Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 8614 insertions, 0 deletions

diff --git a/fs/fat/.kunitconfig b/fs/fat/.kunitconfig
new file mode 100644
index 000000000..0a6971dbe
--- /dev/null
+++ b/fs/fat/.kunitconfig
@@ -0,0 +1,5 @@
+CONFIG_KUNIT=y
+CONFIG_FAT_FS=y
+CONFIG_MSDOS_FS=y
+CONFIG_VFAT_FS=y
+CONFIG_FAT_KUNIT_TEST=y
diff --git a/fs/fat/Kconfig b/fs/fat/Kconfig
new file mode 100644
index 000000000..238cc55f8
--- /dev/null
+++ b/fs/fat/Kconfig
@@ -0,0 +1,129 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config FAT_FS
+	tristate
+	select NLS
+	help
+	  If you want to use one of the FAT-based file systems (the MS-DOS and
+	  VFAT (Windows 95) file systems), then you must say Y or M here
+	  to include FAT support. You will then be able to mount partitions or
+	  diskettes with FAT-based file systems and transparently access the
+	  files on them, i.e. MSDOS files will look and behave just like all
+	  other Unix files.
+
+	  This FAT support is not a file system in itself, it only provides
+	  the foundation for the other file systems. You will have to say Y or
+	  M to at least one of "MSDOS fs support" or "VFAT fs support" in
+	  order to make use of it.
+
+	  Another way to read and write MSDOS floppies and hard drive
+	  partitions from within Linux (but not transparently) is with the
+	  mtools ("man mtools") program suite. You don't need to say Y here in
+	  order to do that.
+
+	  If you need to move large files on floppies between a DOS and a
+	  Linux box, say Y here, mount the floppy under Linux with an MSDOS
+	  file system and use GNU tar's M option. GNU tar is a program
+	  available for Unix and DOS ("man tar" or "info tar").
+
+	  The FAT support will enlarge your kernel by about 37 KB. If unsure,
+	  say Y.
+
+	  To compile this as a module, choose M here: the module will be called
+	  fat.  Note that if you compile the FAT support as a module, you
+	  cannot compile any of the FAT-based file systems into the kernel
+	  -- they will have to be modules as well.
+
+config MSDOS_FS
+	tristate "MSDOS fs support"
+	select FAT_FS
+	help
+	  This allows you to mount MSDOS partitions of your hard drive (unless
+	  they are compressed; to access compressed MSDOS partitions under
+	  Linux, you can either use the DOS emulator DOSEMU, described in the
+	  DOSEMU-HOWTO, available from
+	  <https://www.tldp.org/docs.html#howto>, or try dmsdosfs in
+	  <ftp://ibiblio.org/pub/Linux/system/filesystems/dosfs/>. If you
+	  intend to use dosemu with a non-compressed MSDOS partition, say Y
+	  here) and MSDOS floppies. This means that file access becomes
+	  transparent, i.e. the MSDOS files look and behave just like all
+	  other Unix files.
+
+	  If you have Windows 95 or Windows NT installed on your MSDOS
+	  partitions, you should use the VFAT file system (say Y to "VFAT fs
+	  support" below), or you will not be able to see the long filenames
+	  generated by Windows 95 / Windows NT.
+
+	  This option will enlarge your kernel by about 7 KB. If unsure,
+	  answer Y. This will only work if you said Y to "DOS FAT fs support"
+	  as well. To compile this as a module, choose M here: the module will
+	  be called msdos.
+
+config VFAT_FS
+	tristate "VFAT (Windows-95) fs support"
+	select FAT_FS
+	help
+	  This option provides support for normal Windows file systems with
+	  long filenames.  That includes non-compressed FAT-based file systems
+	  used by Windows 95, Windows 98, Windows NT 4.0, and the Unix
+	  programs from the mtools package.
+
+	  The VFAT support enlarges your kernel by about 10 KB and it only
+	  works if you said Y to the "DOS FAT fs support" above.  Please read
+	  the file <file:Documentation/filesystems/vfat.rst> for details.  If
+	  unsure, say Y.
+
+	  To compile this as a module, choose M here: the module will be called
+	  vfat.
+
+config FAT_DEFAULT_CODEPAGE
+	int "Default codepage for FAT"
+	depends on FAT_FS
+	default 437
+	help
+	  This option should be set to the codepage of your FAT filesystems.
+	  It can be overridden with the "codepage" mount option.
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+config FAT_DEFAULT_IOCHARSET
+	string "Default iocharset for FAT"
+	depends on VFAT_FS
+	default "iso8859-1"
+	help
+	  Set this to the default input/output character set you'd
+	  like FAT to use. It should probably match the character set
+	  that most of your FAT filesystems use, and can be overridden
+	  with the "iocharset" mount option for FAT filesystems.
+	  Note that "utf8" is not recommended for FAT filesystems.
+	  If unsure, you shouldn't set "utf8" here - select the next option
+	  instead if you would like to use UTF-8 encoded file names by default.
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+	  Enable any character sets you need in File Systems/Native Language
+	  Support.
+
+config FAT_DEFAULT_UTF8
+	bool "Enable FAT UTF-8 option by default"
+	depends on VFAT_FS
+	default n
+	help
+	  Set this if you would like to have "utf8" mount option set
+	  by default when mounting FAT filesystems.
+
+	  Even if you say Y here can always disable UTF-8 for
+	  particular mount by adding "utf8=0" to mount options.
+
+	  Say Y if you use UTF-8 encoding for file names, N otherwise.
+
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+config FAT_KUNIT_TEST
+	tristate "Unit Tests for FAT filesystems" if !KUNIT_ALL_TESTS
+	depends on KUNIT && FAT_FS
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the FAT KUnit tests
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit
+
+	  If unsure, say N
diff --git a/fs/fat/Makefile b/fs/fat/Makefile
new file mode 100644
index 000000000..2b0341126
--- /dev/null
+++ b/fs/fat/Makefile
@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux fat filesystem support.
+#
+
+obj-$(CONFIG_FAT_FS) += fat.o
+obj-$(CONFIG_VFAT_FS) += vfat.o
+obj-$(CONFIG_MSDOS_FS) += msdos.o
+
+fat-y := cache.o dir.o fatent.o file.o inode.o misc.o nfs.o
+vfat-y := namei_vfat.o
+msdos-y := namei_msdos.o
+
+obj-$(CONFIG_FAT_KUNIT_TEST) += fat_test.o
diff --git a/fs/fat/cache.c b/fs/fat/cache.c
new file mode 100644
index 000000000..738e427e2
--- /dev/null
+++ b/fs/fat/cache.c
@@ -0,0 +1,386 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/fat/cache.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
+ *	of inode number.
+ *  May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
+ */
+
+#include <linux/slab.h>
+#include "fat.h"
+
+/* this must be > 0. */
+#define FAT_MAX_CACHE	8
+
+struct fat_cache {
+	struct list_head cache_list;
+	int nr_contig;	/* number of contiguous clusters */
+	int fcluster;	/* cluster number in the file. */
+	int dcluster;	/* cluster number on disk. */
+};
+
+struct fat_cache_id {
+	unsigned int id;
+	int nr_contig;
+	int fcluster;
+	int dcluster;
+};
+
+static inline int fat_max_cache(struct inode *inode)
+{
+	return FAT_MAX_CACHE;
+}
+
+static struct kmem_cache *fat_cache_cachep;
+
+static void init_once(void *foo)
+{
+	struct fat_cache *cache = (struct fat_cache *)foo;
+
+	INIT_LIST_HEAD(&cache->cache_list);
+}
+
+int __init fat_cache_init(void)
+{
+	fat_cache_cachep = kmem_cache_create("fat_cache",
+				sizeof(struct fat_cache),
+				0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
+				init_once);
+	if (fat_cache_cachep == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void fat_cache_destroy(void)
+{
+	kmem_cache_destroy(fat_cache_cachep);
+}
+
+static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
+{
+	return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
+}
+
+static inline void fat_cache_free(struct fat_cache *cache)
+{
+	BUG_ON(!list_empty(&cache->cache_list));
+	kmem_cache_free(fat_cache_cachep, cache);
+}
+
+static inline void fat_cache_update_lru(struct inode *inode,
+					struct fat_cache *cache)
+{
+	if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
+		list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
+}
+
+static int fat_cache_lookup(struct inode *inode, int fclus,
+			    struct fat_cache_id *cid,
+			    int *cached_fclus, int *cached_dclus)
+{
+	static struct fat_cache nohit = { .fcluster = 0, };
+
+	struct fat_cache *hit = &nohit, *p;
+	int offset = -1;
+
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+		/* Find the cache of "fclus" or nearest cache. */
+		if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
+			hit = p;
+			if ((hit->fcluster + hit->nr_contig) < fclus) {
+				offset = hit->nr_contig;
+			} else {
+				offset = fclus - hit->fcluster;
+				break;
+			}
+		}
+	}
+	if (hit != &nohit) {
+		fat_cache_update_lru(inode, hit);
+
+		cid->id = MSDOS_I(inode)->cache_valid_id;
+		cid->nr_contig = hit->nr_contig;
+		cid->fcluster = hit->fcluster;
+		cid->dcluster = hit->dcluster;
+		*cached_fclus = cid->fcluster + offset;
+		*cached_dclus = cid->dcluster + offset;
+	}
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+
+	return offset;
+}
+
+static struct fat_cache *fat_cache_merge(struct inode *inode,
+					 struct fat_cache_id *new)
+{
+	struct fat_cache *p;
+
+	list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+		/* Find the same part as "new" in cluster-chain. */
+		if (p->fcluster == new->fcluster) {
+			BUG_ON(p->dcluster != new->dcluster);
+			if (new->nr_contig > p->nr_contig)
+				p->nr_contig = new->nr_contig;
+			return p;
+		}
+	}
+	return NULL;
+}
+
+static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
+{
+	struct fat_cache *cache, *tmp;
+
+	if (new->fcluster == -1) /* dummy cache */
+		return;
+
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	if (new->id != FAT_CACHE_VALID &&
+	    new->id != MSDOS_I(inode)->cache_valid_id)
+		goto out;	/* this cache was invalidated */
+
+	cache = fat_cache_merge(inode, new);
+	if (cache == NULL) {
+		if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
+			MSDOS_I(inode)->nr_caches++;
+			spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+
+			tmp = fat_cache_alloc(inode);
+			if (!tmp) {
+				spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+				MSDOS_I(inode)->nr_caches--;
+				spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+				return;
+			}
+
+			spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+			cache = fat_cache_merge(inode, new);
+			if (cache != NULL) {
+				MSDOS_I(inode)->nr_caches--;
+				fat_cache_free(tmp);
+				goto out_update_lru;
+			}
+			cache = tmp;
+		} else {
+			struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
+			cache = list_entry(p, struct fat_cache, cache_list);
+		}
+		cache->fcluster = new->fcluster;
+		cache->dcluster = new->dcluster;
+		cache->nr_contig = new->nr_contig;
+	}
+out_update_lru:
+	fat_cache_update_lru(inode, cache);
+out:
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+}
+
+/*
+ * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
+ * fixes itself after a while.
+ */
+static void __fat_cache_inval_inode(struct inode *inode)
+{
+	struct msdos_inode_info *i = MSDOS_I(inode);
+	struct fat_cache *cache;
+
+	while (!list_empty(&i->cache_lru)) {
+		cache = list_entry(i->cache_lru.next,
+				   struct fat_cache, cache_list);
+		list_del_init(&cache->cache_list);
+		i->nr_caches--;
+		fat_cache_free(cache);
+	}
+	/* Update. The copy of caches before this id is discarded. */
+	i->cache_valid_id++;
+	if (i->cache_valid_id == FAT_CACHE_VALID)
+		i->cache_valid_id++;
+}
+
+void fat_cache_inval_inode(struct inode *inode)
+{
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	__fat_cache_inval_inode(inode);
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+}
+
+static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
+{
+	cid->nr_contig++;
+	return ((cid->dcluster + cid->nr_contig) == dclus);
+}
+
+static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
+{
+	cid->id = FAT_CACHE_VALID;
+	cid->fcluster = fclus;
+	cid->dcluster = dclus;
+	cid->nr_contig = 0;
+}
+
+int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const int limit = sb->s_maxbytes >> sbi->cluster_bits;
+	struct fat_entry fatent;
+	struct fat_cache_id cid;
+	int nr;
+
+	BUG_ON(MSDOS_I(inode)->i_start == 0);
+
+	*fclus = 0;
+	*dclus = MSDOS_I(inode)->i_start;
+	if (!fat_valid_entry(sbi, *dclus)) {
+		fat_fs_error_ratelimit(sb,
+			"%s: invalid start cluster (i_pos %lld, start %08x)",
+			__func__, MSDOS_I(inode)->i_pos, *dclus);
+		return -EIO;
+	}
+	if (cluster == 0)
+		return 0;
+
+	if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
+		/*
+		 * dummy, always not contiguous
+		 * This is reinitialized by cache_init(), later.
+		 */
+		cache_init(&cid, -1, -1);
+	}
+
+	fatent_init(&fatent);
+	while (*fclus < cluster) {
+		/* prevent the infinite loop of cluster chain */
+		if (*fclus > limit) {
+			fat_fs_error_ratelimit(sb,
+				"%s: detected the cluster chain loop (i_pos %lld)",
+				__func__, MSDOS_I(inode)->i_pos);
+			nr = -EIO;
+			goto out;
+		}
+
+		nr = fat_ent_read(inode, &fatent, *dclus);
+		if (nr < 0)
+			goto out;
+		else if (nr == FAT_ENT_FREE) {
+			fat_fs_error_ratelimit(sb,
+				"%s: invalid cluster chain (i_pos %lld)",
+				__func__, MSDOS_I(inode)->i_pos);
+			nr = -EIO;
+			goto out;
+		} else if (nr == FAT_ENT_EOF) {
+			fat_cache_add(inode, &cid);
+			goto out;
+		}
+		(*fclus)++;
+		*dclus = nr;
+		if (!cache_contiguous(&cid, *dclus))
+			cache_init(&cid, *fclus, *dclus);
+	}
+	nr = 0;
+	fat_cache_add(inode, &cid);
+out:
+	fatent_brelse(&fatent);
+	return nr;
+}
+
+static int fat_bmap_cluster(struct inode *inode, int cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret, fclus, dclus;
+
+	if (MSDOS_I(inode)->i_start == 0)
+		return 0;
+
+	ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
+	if (ret < 0)
+		return ret;
+	else if (ret == FAT_ENT_EOF) {
+		fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
+			     __func__, MSDOS_I(inode)->i_pos);
+		return -EIO;
+	}
+	return dclus;
+}
+
+int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
+			   sector_t last_block,
+			   unsigned long *mapped_blocks, sector_t *bmap)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int cluster, offset;
+
+	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
+	offset  = sector & (sbi->sec_per_clus - 1);
+	cluster = fat_bmap_cluster(inode, cluster);
+	if (cluster < 0)
+		return cluster;
+	else if (cluster) {
+		*bmap = fat_clus_to_blknr(sbi, cluster) + offset;
+		*mapped_blocks = sbi->sec_per_clus - offset;
+		if (*mapped_blocks > last_block - sector)
+			*mapped_blocks = last_block - sector;
+	}
+
+	return 0;
+}
+
+static int is_exceed_eof(struct inode *inode, sector_t sector,
+			 sector_t *last_block, int create)
+{
+	struct super_block *sb = inode->i_sb;
+	const unsigned long blocksize = sb->s_blocksize;
+	const unsigned char blocksize_bits = sb->s_blocksize_bits;
+
+	*last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
+	if (sector >= *last_block) {
+		if (!create)
+			return 1;
+
+		/*
+		 * ->mmu_private can access on only allocation path.
+		 * (caller must hold ->i_mutex)
+		 */
+		*last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
+			>> blocksize_bits;
+		if (sector >= *last_block)
+			return 1;
+	}
+
+	return 0;
+}
+
+int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
+	     unsigned long *mapped_blocks, int create, bool from_bmap)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	sector_t last_block;
+
+	*phys = 0;
+	*mapped_blocks = 0;
+	if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
+		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
+			*phys = sector + sbi->dir_start;
+			*mapped_blocks = 1;
+		}
+		return 0;
+	}
+
+	if (!from_bmap) {
+		if (is_exceed_eof(inode, sector, &last_block, create))
+			return 0;
+	} else {
+		last_block = inode->i_blocks >>
+				(inode->i_sb->s_blocksize_bits - 9);
+		if (sector >= last_block)
+			return 0;
+	}
+
+	return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
+				      phys);
+}
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
new file mode 100644
index 000000000..00235b8a1
--- /dev/null
+++ b/fs/fat/dir.c
@@ -0,0 +1,1414 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/dir.c
+ *
+ *  directory handling functions for fat-based filesystems
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
+ *
+ *  VFAT extensions by Gordon Chaffee <chaffee@plateau.cs.berkeley.edu>
+ *  Merged with msdos fs by Henrik Storner <storner@osiris.ping.dk>
+ *  Rewritten for constant inumbers. Plugged buffer overrun in readdir(). AV
+ *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
+ */
+
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/uaccess.h>
+#include <linux/iversion.h>
+#include "fat.h"
+
+/*
+ * Maximum buffer size of short name.
+ * [(MSDOS_NAME + '.') * max one char + nul]
+ * For msdos style, ['.' (hidden) + MSDOS_NAME + '.' + nul]
+ */
+#define FAT_MAX_SHORT_SIZE	((MSDOS_NAME + 1) * NLS_MAX_CHARSET_SIZE + 1)
+/*
+ * Maximum buffer size of unicode chars from slots.
+ * [(max longname slots * 13 (size in a slot) + nul) * sizeof(wchar_t)]
+ */
+#define FAT_MAX_UNI_CHARS	((MSDOS_SLOTS - 1) * 13 + 1)
+#define FAT_MAX_UNI_SIZE	(FAT_MAX_UNI_CHARS * sizeof(wchar_t))
+
+static inline unsigned char fat_tolower(unsigned char c)
+{
+	return ((c >= 'A') && (c <= 'Z')) ? c+32 : c;
+}
+
+static inline loff_t fat_make_i_pos(struct super_block *sb,
+				    struct buffer_head *bh,
+				    struct msdos_dir_entry *de)
+{
+	return ((loff_t)bh->b_blocknr << MSDOS_SB(sb)->dir_per_block_bits)
+		| (de - (struct msdos_dir_entry *)bh->b_data);
+}
+
+static inline void fat_dir_readahead(struct inode *dir, sector_t iblock,
+				     sector_t phys)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	int sec;
+
+	/* This is not a first sector of cluster, or sec_per_clus == 1 */
+	if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
+		return;
+	/* root dir of FAT12/FAT16 */
+	if (!is_fat32(sbi) && (dir->i_ino == MSDOS_ROOT_INO))
+		return;
+
+	bh = sb_find_get_block(sb, phys);
+	if (bh == NULL || !buffer_uptodate(bh)) {
+		for (sec = 0; sec < sbi->sec_per_clus; sec++)
+			sb_breadahead(sb, phys + sec);
+	}
+	brelse(bh);
+}
+
+/* Returns the inode number of the directory entry at offset pos. If bh is
+   non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
+   returned in bh.
+   AV. Most often we do it item-by-item. Makes sense to optimize.
+   AV. OK, there we go: if both bh and de are non-NULL we assume that we just
+   AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
+   AV. It's done in fat_get_entry() (inlined), here the slow case lives.
+   AV. Additionally, when we return -1 (i.e. reached the end of directory)
+   AV. we make bh NULL.
+ */
+static int fat__get_entry(struct inode *dir, loff_t *pos,
+			  struct buffer_head **bh, struct msdos_dir_entry **de)
+{
+	struct super_block *sb = dir->i_sb;
+	sector_t phys, iblock;
+	unsigned long mapped_blocks;
+	int err, offset;
+
+next:
+	brelse(*bh);
+	*bh = NULL;
+	iblock = *pos >> sb->s_blocksize_bits;
+	err = fat_bmap(dir, iblock, &phys, &mapped_blocks, 0, false);
+	if (err || !phys)
+		return -1;	/* beyond EOF or error */
+
+	fat_dir_readahead(dir, iblock, phys);
+
+	*bh = sb_bread(sb, phys);
+	if (*bh == NULL) {
+		fat_msg_ratelimit(sb, KERN_ERR,
+			"Directory bread(block %llu) failed", (llu)phys);
+		/* skip this block */
+		*pos = (iblock + 1) << sb->s_blocksize_bits;
+		goto next;
+	}
+
+	offset = *pos & (sb->s_blocksize - 1);
+	*pos += sizeof(struct msdos_dir_entry);
+	*de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
+
+	return 0;
+}
+
+static inline int fat_get_entry(struct inode *dir, loff_t *pos,
+				struct buffer_head **bh,
+				struct msdos_dir_entry **de)
+{
+	/* Fast stuff first */
+	if (*bh && *de &&
+	   (*de - (struct msdos_dir_entry *)(*bh)->b_data) <
+				MSDOS_SB(dir->i_sb)->dir_per_block - 1) {
+		*pos += sizeof(struct msdos_dir_entry);
+		(*de)++;
+		return 0;
+	}
+	return fat__get_entry(dir, pos, bh, de);
+}
+
+/*
+ * Convert Unicode 16 to UTF-8, translated Unicode, or ASCII.
+ * If uni_xlate is enabled and we can't get a 1:1 conversion, use a
+ * colon as an escape character since it is normally invalid on the vfat
+ * filesystem. The following four characters are the hexadecimal digits
+ * of Unicode value. This lets us do a full dump and restore of Unicode
+ * filenames. We could get into some trouble with long Unicode names,
+ * but ignore that right now.
+ * Ahem... Stack smashing in ring 0 isn't fun. Fixed.
+ */
+static int uni16_to_x8(struct super_block *sb, unsigned char *ascii,
+		       const wchar_t *uni, int len, struct nls_table *nls)
+{
+	int uni_xlate = MSDOS_SB(sb)->options.unicode_xlate;
+	const wchar_t *ip;
+	wchar_t ec;
+	unsigned char *op;
+	int charlen;
+
+	ip = uni;
+	op = ascii;
+
+	while (*ip && ((len - NLS_MAX_CHARSET_SIZE) > 0)) {
+		ec = *ip++;
+		charlen = nls->uni2char(ec, op, NLS_MAX_CHARSET_SIZE);
+		if (charlen > 0) {
+			op += charlen;
+			len -= charlen;
+		} else {
+			if (uni_xlate == 1) {
+				*op++ = ':';
+				op = hex_byte_pack(op, ec >> 8);
+				op = hex_byte_pack(op, ec);
+				len -= 5;
+			} else {
+				*op++ = '?';
+				len--;
+			}
+		}
+	}
+
+	if (unlikely(*ip)) {
+		fat_msg(sb, KERN_WARNING,
+			"filename was truncated while converting.");
+	}
+
+	*op = 0;
+	return op - ascii;
+}
+
+static inline int fat_uni_to_x8(struct super_block *sb, const wchar_t *uni,
+				unsigned char *buf, int size)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	if (sbi->options.utf8)
+		return utf16s_to_utf8s(uni, FAT_MAX_UNI_CHARS,
+				UTF16_HOST_ENDIAN, buf, size);
+	else
+		return uni16_to_x8(sb, buf, uni, size, sbi->nls_io);
+}
+
+static inline int
+fat_short2uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
+{
+	int charlen;
+
+	charlen = t->char2uni(c, clen, uni);
+	if (charlen < 0) {
+		*uni = 0x003f;	/* a question mark */
+		charlen = 1;
+	}
+	return charlen;
+}
+
+static inline int
+fat_short2lower_uni(struct nls_table *t, unsigned char *c,
+		    int clen, wchar_t *uni)
+{
+	int charlen;
+	wchar_t wc;
+
+	charlen = t->char2uni(c, clen, &wc);
+	if (charlen < 0) {
+		*uni = 0x003f;	/* a question mark */
+		charlen = 1;
+	} else if (charlen <= 1) {
+		unsigned char nc = t->charset2lower[*c];
+
+		if (!nc)
+			nc = *c;
+
+		charlen = t->char2uni(&nc, 1, uni);
+		if (charlen < 0) {
+			*uni = 0x003f;	/* a question mark */
+			charlen = 1;
+		}
+	} else
+		*uni = wc;
+
+	return charlen;
+}
+
+static inline int
+fat_shortname2uni(struct nls_table *nls, unsigned char *buf, int buf_size,
+		  wchar_t *uni_buf, unsigned short opt, int lower)
+{
+	int len = 0;
+
+	if (opt & VFAT_SFN_DISPLAY_LOWER)
+		len =  fat_short2lower_uni(nls, buf, buf_size, uni_buf);
+	else if (opt & VFAT_SFN_DISPLAY_WIN95)
+		len = fat_short2uni(nls, buf, buf_size, uni_buf);
+	else if (opt & VFAT_SFN_DISPLAY_WINNT) {
+		if (lower)
+			len = fat_short2lower_uni(nls, buf, buf_size, uni_buf);
+		else
+			len = fat_short2uni(nls, buf, buf_size, uni_buf);
+	} else
+		len = fat_short2uni(nls, buf, buf_size, uni_buf);
+
+	return len;
+}
+
+static inline int fat_name_match(struct msdos_sb_info *sbi,
+				 const unsigned char *a, int a_len,
+				 const unsigned char *b, int b_len)
+{
+	if (a_len != b_len)
+		return 0;
+
+	if (sbi->options.name_check != 's')
+		return !nls_strnicmp(sbi->nls_io, a, b, a_len);
+	else
+		return !memcmp(a, b, a_len);
+}
+
+enum { PARSE_INVALID = 1, PARSE_NOT_LONGNAME, PARSE_EOF, };
+
+/**
+ * fat_parse_long - Parse extended directory entry.
+ *
+ * This function returns zero on success, negative value on error, or one of
+ * the following:
+ *
+ * %PARSE_INVALID - Directory entry is invalid.
+ * %PARSE_NOT_LONGNAME - Directory entry does not contain longname.
+ * %PARSE_EOF - Directory has no more entries.
+ */
+static int fat_parse_long(struct inode *dir, loff_t *pos,
+			  struct buffer_head **bh, struct msdos_dir_entry **de,
+			  wchar_t **unicode, unsigned char *nr_slots)
+{
+	struct msdos_dir_slot *ds;
+	unsigned char id, slot, slots, alias_checksum;
+
+	if (!*unicode) {
+		*unicode = __getname();
+		if (!*unicode) {
+			brelse(*bh);
+			return -ENOMEM;
+		}
+	}
+parse_long:
+	ds = (struct msdos_dir_slot *)*de;
+	id = ds->id;
+	if (!(id & 0x40))
+		return PARSE_INVALID;
+	slots = id & ~0x40;
+	if (slots > 20 || !slots)	/* ceil(256 * 2 / 26) */
+		return PARSE_INVALID;
+	*nr_slots = slots;
+	alias_checksum = ds->alias_checksum;
+
+	slot = slots;
+	while (1) {
+		int offset;
+
+		slot--;
+		offset = slot * 13;
+		fat16_towchar(*unicode + offset, ds->name0_4, 5);
+		fat16_towchar(*unicode + offset + 5, ds->name5_10, 6);
+		fat16_towchar(*unicode + offset + 11, ds->name11_12, 2);
+
+		if (ds->id & 0x40)
+			(*unicode)[offset + 13] = 0;
+		if (fat_get_entry(dir, pos, bh, de) < 0)
+			return PARSE_EOF;
+		if (slot == 0)
+			break;
+		ds = (struct msdos_dir_slot *)*de;
+		if (ds->attr != ATTR_EXT)
+			return PARSE_NOT_LONGNAME;
+		if ((ds->id & ~0x40) != slot)
+			goto parse_long;
+		if (ds->alias_checksum != alias_checksum)
+			goto parse_long;
+	}
+	if ((*de)->name[0] == DELETED_FLAG)
+		return PARSE_INVALID;
+	if ((*de)->attr == ATTR_EXT)
+		goto parse_long;
+	if (IS_FREE((*de)->name) || ((*de)->attr & ATTR_VOLUME))
+		return PARSE_INVALID;
+	if (fat_checksum((*de)->name) != alias_checksum)
+		*nr_slots = 0;
+
+	return 0;
+}
+
+/**
+ * fat_parse_short - Parse MS-DOS (short) directory entry.
+ * @sb:		superblock
+ * @de:		directory entry to parse
+ * @name:	FAT_MAX_SHORT_SIZE array in which to place extracted name
+ * @dot_hidden:	Nonzero == prepend '.' to names with ATTR_HIDDEN
+ *
+ * Returns the number of characters extracted into 'name'.
+ */
+static int fat_parse_short(struct super_block *sb,
+			   const struct msdos_dir_entry *de,
+			   unsigned char *name, int dot_hidden)
+{
+	const struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int isvfat = sbi->options.isvfat;
+	int nocase = sbi->options.nocase;
+	unsigned short opt_shortname = sbi->options.shortname;
+	struct nls_table *nls_disk = sbi->nls_disk;
+	wchar_t uni_name[14];
+	unsigned char c, work[MSDOS_NAME];
+	unsigned char *ptname = name;
+	int chi, chl, i, j, k;
+	int dotoffset = 0;
+	int name_len = 0, uni_len = 0;
+
+	if (!isvfat && dot_hidden && (de->attr & ATTR_HIDDEN)) {
+		*ptname++ = '.';
+		dotoffset = 1;
+	}
+
+	memcpy(work, de->name, sizeof(work));
+	/* For an explanation of the special treatment of 0x05 in
+	 * filenames, see msdos_format_name in namei_msdos.c
+	 */
+	if (work[0] == 0x05)
+		work[0] = 0xE5;
+
+	/* Filename */
+	for (i = 0, j = 0; i < 8;) {
+		c = work[i];
+		if (!c)
+			break;
+		chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
+					&uni_name[j++], opt_shortname,
+					de->lcase & CASE_LOWER_BASE);
+		if (chl <= 1) {
+			if (!isvfat)
+				ptname[i] = nocase ? c : fat_tolower(c);
+			i++;
+			if (c != ' ') {
+				name_len = i;
+				uni_len  = j;
+			}
+		} else {
+			uni_len = j;
+			if (isvfat)
+				i += min(chl, 8-i);
+			else {
+				for (chi = 0; chi < chl && i < 8; chi++, i++)
+					ptname[i] = work[i];
+			}
+			if (chl)
+				name_len = i;
+		}
+	}
+
+	i = name_len;
+	j = uni_len;
+	fat_short2uni(nls_disk, ".", 1, &uni_name[j++]);
+	if (!isvfat)
+		ptname[i] = '.';
+	i++;
+
+	/* Extension */
+	for (k = 8; k < MSDOS_NAME;) {
+		c = work[k];
+		if (!c)
+			break;
+		chl = fat_shortname2uni(nls_disk, &work[k], MSDOS_NAME - k,
+					&uni_name[j++], opt_shortname,
+					de->lcase & CASE_LOWER_EXT);
+		if (chl <= 1) {
+			k++;
+			if (!isvfat)
+				ptname[i] = nocase ? c : fat_tolower(c);
+			i++;
+			if (c != ' ') {
+				name_len = i;
+				uni_len  = j;
+			}
+		} else {
+			uni_len = j;
+			if (isvfat) {
+				int offset = min(chl, MSDOS_NAME-k);
+				k += offset;
+				i += offset;
+			} else {
+				for (chi = 0; chi < chl && k < MSDOS_NAME;
+				     chi++, i++, k++) {
+						ptname[i] = work[k];
+				}
+			}
+			if (chl)
+				name_len = i;
+		}
+	}
+
+	if (name_len > 0) {
+		name_len += dotoffset;
+
+		if (sbi->options.isvfat) {
+			uni_name[uni_len] = 0x0000;
+			name_len = fat_uni_to_x8(sb, uni_name, name,
+						 FAT_MAX_SHORT_SIZE);
+		}
+	}
+
+	return name_len;
+}
+
+/*
+ * Return values: negative -> error/not found, 0 -> found.
+ */
+int fat_search_long(struct inode *inode, const unsigned char *name,
+		    int name_len, struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh = NULL;
+	struct msdos_dir_entry *de;
+	unsigned char nr_slots;
+	wchar_t *unicode = NULL;
+	unsigned char bufname[FAT_MAX_SHORT_SIZE];
+	loff_t cpos = 0;
+	int err, len;
+
+	err = -ENOENT;
+	while (1) {
+		if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
+			goto end_of_dir;
+parse_record:
+		nr_slots = 0;
+		if (de->name[0] == DELETED_FLAG)
+			continue;
+		if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
+			continue;
+		if (de->attr != ATTR_EXT && IS_FREE(de->name))
+			continue;
+		if (de->attr == ATTR_EXT) {
+			int status = fat_parse_long(inode, &cpos, &bh, &de,
+						    &unicode, &nr_slots);
+			if (status < 0) {
+				err = status;
+				goto end_of_dir;
+			} else if (status == PARSE_INVALID)
+				continue;
+			else if (status == PARSE_NOT_LONGNAME)
+				goto parse_record;
+			else if (status == PARSE_EOF)
+				goto end_of_dir;
+		}
+
+		/* Never prepend '.' to hidden files here.
+		 * That is done only for msdos mounts (and only when
+		 * 'dotsOK=yes'); if we are executing here, it is in the
+		 * context of a vfat mount.
+		 */
+		len = fat_parse_short(sb, de, bufname, 0);
+		if (len == 0)
+			continue;
+
+		/* Compare shortname */
+		if (fat_name_match(sbi, name, name_len, bufname, len))
+			goto found;
+
+		if (nr_slots) {
+			void *longname = unicode + FAT_MAX_UNI_CHARS;
+			int size = PATH_MAX - FAT_MAX_UNI_SIZE;
+
+			/* Compare longname */
+			len = fat_uni_to_x8(sb, unicode, longname, size);
+			if (fat_name_match(sbi, name, name_len, longname, len))
+				goto found;
+		}
+	}
+
+found:
+	nr_slots++;	/* include the de */
+	sinfo->slot_off = cpos - nr_slots * sizeof(*de);
+	sinfo->nr_slots = nr_slots;
+	sinfo->de = de;
+	sinfo->bh = bh;
+	sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
+	err = 0;
+end_of_dir:
+	if (unicode)
+		__putname(unicode);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(fat_search_long);
+
+struct fat_ioctl_filldir_callback {
+	struct dir_context ctx;
+	void __user *dirent;
+	int result;
+	/* for dir ioctl */
+	const char *longname;
+	int long_len;
+	const char *shortname;
+	int short_len;
+};
+
+static int __fat_readdir(struct inode *inode, struct file *file,
+			 struct dir_context *ctx, int short_only,
+			 struct fat_ioctl_filldir_callback *both)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	struct msdos_dir_entry *de;
+	unsigned char nr_slots;
+	wchar_t *unicode = NULL;
+	unsigned char bufname[FAT_MAX_SHORT_SIZE];
+	int isvfat = sbi->options.isvfat;
+	const char *fill_name = NULL;
+	int fake_offset = 0;
+	loff_t cpos;
+	int short_len = 0, fill_len = 0;
+	int ret = 0;
+
+	mutex_lock(&sbi->s_lock);
+
+	cpos = ctx->pos;
+	/* Fake . and .. for the root directory. */
+	if (inode->i_ino == MSDOS_ROOT_INO) {
+		if (!dir_emit_dots(file, ctx))
+			goto out;
+		if (ctx->pos == 2) {
+			fake_offset = 1;
+			cpos = 0;
+		}
+	}
+	if (cpos & (sizeof(struct msdos_dir_entry) - 1)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	bh = NULL;
+get_new:
+	if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
+		goto end_of_dir;
+parse_record:
+	nr_slots = 0;
+	/*
+	 * Check for long filename entry, but if short_only, we don't
+	 * need to parse long filename.
+	 */
+	if (isvfat && !short_only) {
+		if (de->name[0] == DELETED_FLAG)
+			goto record_end;
+		if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
+			goto record_end;
+		if (de->attr != ATTR_EXT && IS_FREE(de->name))
+			goto record_end;
+	} else {
+		if ((de->attr & ATTR_VOLUME) || IS_FREE(de->name))
+			goto record_end;
+	}
+
+	if (isvfat && de->attr == ATTR_EXT) {
+		int status = fat_parse_long(inode, &cpos, &bh, &de,
+					    &unicode, &nr_slots);
+		if (status < 0) {
+			bh = NULL;
+			ret = status;
+			goto end_of_dir;
+		} else if (status == PARSE_INVALID)
+			goto record_end;
+		else if (status == PARSE_NOT_LONGNAME)
+			goto parse_record;
+		else if (status == PARSE_EOF)
+			goto end_of_dir;
+
+		if (nr_slots) {
+			void *longname = unicode + FAT_MAX_UNI_CHARS;
+			int size = PATH_MAX - FAT_MAX_UNI_SIZE;
+			int len = fat_uni_to_x8(sb, unicode, longname, size);
+
+			fill_name = longname;
+			fill_len = len;
+			/* !both && !short_only, so we don't need shortname. */
+			if (!both)
+				goto start_filldir;
+
+			short_len = fat_parse_short(sb, de, bufname,
+						    sbi->options.dotsOK);
+			if (short_len == 0)
+				goto record_end;
+			/* hack for fat_ioctl_filldir() */
+			both->longname = fill_name;
+			both->long_len = fill_len;
+			both->shortname = bufname;
+			both->short_len = short_len;
+			fill_name = NULL;
+			fill_len = 0;
+			goto start_filldir;
+		}
+	}
+
+	short_len = fat_parse_short(sb, de, bufname, sbi->options.dotsOK);
+	if (short_len == 0)
+		goto record_end;
+
+	fill_name = bufname;
+	fill_len = short_len;
+
+start_filldir:
+	ctx->pos = cpos - (nr_slots + 1) * sizeof(struct msdos_dir_entry);
+	if (fake_offset && ctx->pos < 2)
+		ctx->pos = 2;
+
+	if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME)) {
+		if (!dir_emit_dot(file, ctx))
+			goto fill_failed;
+	} else if (!memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
+		if (!dir_emit_dotdot(file, ctx))
+			goto fill_failed;
+	} else {
+		unsigned long inum;
+		loff_t i_pos = fat_make_i_pos(sb, bh, de);
+		struct inode *tmp = fat_iget(sb, i_pos);
+		if (tmp) {
+			inum = tmp->i_ino;
+			iput(tmp);
+		} else
+			inum = iunique(sb, MSDOS_ROOT_INO);
+		if (!dir_emit(ctx, fill_name, fill_len, inum,
+			    (de->attr & ATTR_DIR) ? DT_DIR : DT_REG))
+			goto fill_failed;
+	}
+
+record_end:
+	fake_offset = 0;
+	ctx->pos = cpos;
+	goto get_new;
+
+end_of_dir:
+	if (fake_offset && cpos < 2)
+		ctx->pos = 2;
+	else
+		ctx->pos = cpos;
+fill_failed:
+	brelse(bh);
+	if (unicode)
+		__putname(unicode);
+out:
+	mutex_unlock(&sbi->s_lock);
+
+	return ret;
+}
+
+static int fat_readdir(struct file *file, struct dir_context *ctx)
+{
+	return __fat_readdir(file_inode(file), file, ctx, 0, NULL);
+}
+
+#define FAT_IOCTL_FILLDIR_FUNC(func, dirent_type)			   \
+static bool func(struct dir_context *ctx, const char *name, int name_len,  \
+			     loff_t offset, u64 ino, unsigned int d_type)  \
+{									   \
+	struct fat_ioctl_filldir_callback *buf =			   \
+		container_of(ctx, struct fat_ioctl_filldir_callback, ctx); \
+	struct dirent_type __user *d1 = buf->dirent;			   \
+	struct dirent_type __user *d2 = d1 + 1;				   \
+									   \
+	if (buf->result)						   \
+		return false;						   \
+	buf->result++;							   \
+									   \
+	if (name != NULL) {						   \
+		/* dirent has only short name */			   \
+		if (name_len >= sizeof(d1->d_name))			   \
+			name_len = sizeof(d1->d_name) - 1;		   \
+									   \
+		if (put_user(0, &d2->d_name[0])			||	   \
+		    put_user(0, &d2->d_reclen)			||	   \
+		    copy_to_user(d1->d_name, name, name_len)	||	   \
+		    put_user(0, d1->d_name + name_len)		||	   \
+		    put_user(name_len, &d1->d_reclen))			   \
+			goto efault;					   \
+	} else {							   \
+		/* dirent has short and long name */			   \
+		const char *longname = buf->longname;			   \
+		int long_len = buf->long_len;				   \
+		const char *shortname = buf->shortname;			   \
+		int short_len = buf->short_len;				   \
+									   \
+		if (long_len >= sizeof(d1->d_name))			   \
+			long_len = sizeof(d1->d_name) - 1;		   \
+		if (short_len >= sizeof(d1->d_name))			   \
+			short_len = sizeof(d1->d_name) - 1;		   \
+									   \
+		if (copy_to_user(d2->d_name, longname, long_len)	|| \
+		    put_user(0, d2->d_name + long_len)			|| \
+		    put_user(long_len, &d2->d_reclen)			|| \
+		    put_user(ino, &d2->d_ino)				|| \
+		    put_user(offset, &d2->d_off)			|| \
+		    copy_to_user(d1->d_name, shortname, short_len)	|| \
+		    put_user(0, d1->d_name + short_len)			|| \
+		    put_user(short_len, &d1->d_reclen))			   \
+			goto efault;					   \
+	}								   \
+	return true;							   \
+efault:									   \
+	buf->result = -EFAULT;						   \
+	return false;							   \
+}
+
+FAT_IOCTL_FILLDIR_FUNC(fat_ioctl_filldir, __fat_dirent)
+
+static int fat_ioctl_readdir(struct inode *inode, struct file *file,
+			     void __user *dirent, filldir_t filldir,
+			     int short_only, int both)
+{
+	struct fat_ioctl_filldir_callback buf = {
+		.ctx.actor = filldir,
+		.dirent = dirent
+	};
+	int ret;
+
+	buf.dirent = dirent;
+	buf.result = 0;
+	inode_lock_shared(inode);
+	buf.ctx.pos = file->f_pos;
+	ret = -ENOENT;
+	if (!IS_DEADDIR(inode)) {
+		ret = __fat_readdir(inode, file, &buf.ctx,
+				    short_only, both ? &buf : NULL);
+		file->f_pos = buf.ctx.pos;
+	}
+	inode_unlock_shared(inode);
+	if (ret >= 0)
+		ret = buf.result;
+	return ret;
+}
+
+static long fat_dir_ioctl(struct file *filp, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	struct __fat_dirent __user *d1 = (struct __fat_dirent __user *)arg;
+	int short_only, both;
+
+	switch (cmd) {
+	case VFAT_IOCTL_READDIR_SHORT:
+		short_only = 1;
+		both = 0;
+		break;
+	case VFAT_IOCTL_READDIR_BOTH:
+		short_only = 0;
+		both = 1;
+		break;
+	default:
+		return fat_generic_ioctl(filp, cmd, arg);
+	}
+
+	/*
+	 * Yes, we don't need this put_user() absolutely. However old
+	 * code didn't return the right value. So, app use this value,
+	 * in order to check whether it is EOF.
+	 */
+	if (put_user(0, &d1->d_reclen))
+		return -EFAULT;
+
+	return fat_ioctl_readdir(inode, filp, d1, fat_ioctl_filldir,
+				 short_only, both);
+}
+
+#ifdef CONFIG_COMPAT
+#define	VFAT_IOCTL_READDIR_BOTH32	_IOR('r', 1, struct compat_dirent[2])
+#define	VFAT_IOCTL_READDIR_SHORT32	_IOR('r', 2, struct compat_dirent[2])
+
+FAT_IOCTL_FILLDIR_FUNC(fat_compat_ioctl_filldir, compat_dirent)
+
+static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
+				 unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	struct compat_dirent __user *d1 = compat_ptr(arg);
+	int short_only, both;
+
+	switch (cmd) {
+	case VFAT_IOCTL_READDIR_SHORT32:
+		short_only = 1;
+		both = 0;
+		break;
+	case VFAT_IOCTL_READDIR_BOTH32:
+		short_only = 0;
+		both = 1;
+		break;
+	default:
+		return fat_generic_ioctl(filp, cmd, (unsigned long)arg);
+	}
+
+	/*
+	 * Yes, we don't need this put_user() absolutely. However old
+	 * code didn't return the right value. So, app use this value,
+	 * in order to check whether it is EOF.
+	 */
+	if (put_user(0, &d1->d_reclen))
+		return -EFAULT;
+
+	return fat_ioctl_readdir(inode, filp, d1, fat_compat_ioctl_filldir,
+				 short_only, both);
+}
+#endif /* CONFIG_COMPAT */
+
+const struct file_operations fat_dir_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= fat_readdir,
+	.unlocked_ioctl	= fat_dir_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= fat_compat_dir_ioctl,
+#endif
+	.fsync		= fat_file_fsync,
+};
+
+static int fat_get_short_entry(struct inode *dir, loff_t *pos,
+			       struct buffer_head **bh,
+			       struct msdos_dir_entry **de)
+{
+	while (fat_get_entry(dir, pos, bh, de) >= 0) {
+		/* free entry or long name entry or volume label */
+		if (!IS_FREE((*de)->name) && !((*de)->attr & ATTR_VOLUME))
+			return 0;
+	}
+	return -ENOENT;
+}
+
+/*
+ * The ".." entry can not provide the "struct fat_slot_info" information
+ * for inode, nor a usable i_pos. So, this function provides some information
+ * only.
+ *
+ * Since this function walks through the on-disk inodes within a directory,
+ * callers are responsible for taking any locks necessary to prevent the
+ * directory from changing.
+ */
+int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
+			 struct msdos_dir_entry **de)
+{
+	loff_t offset = 0;
+
+	*de = NULL;
+	while (fat_get_short_entry(dir, &offset, bh, de) >= 0) {
+		if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME))
+			return 0;
+	}
+	return -ENOENT;
+}
+EXPORT_SYMBOL_GPL(fat_get_dotdot_entry);
+
+/* See if directory is empty */
+int fat_dir_empty(struct inode *dir)
+{
+	struct buffer_head *bh;
+	struct msdos_dir_entry *de;
+	loff_t cpos;
+	int result = 0;
+
+	bh = NULL;
+	cpos = 0;
+	while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
+		if (strncmp(de->name, MSDOS_DOT   , MSDOS_NAME) &&
+		    strncmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
+			result = -ENOTEMPTY;
+			break;
+		}
+	}
+	brelse(bh);
+	return result;
+}
+EXPORT_SYMBOL_GPL(fat_dir_empty);
+
+/*
+ * fat_subdirs counts the number of sub-directories of dir. It can be run
+ * on directories being created.
+ */
+int fat_subdirs(struct inode *dir)
+{
+	struct buffer_head *bh;
+	struct msdos_dir_entry *de;
+	loff_t cpos;
+	int count = 0;
+
+	bh = NULL;
+	cpos = 0;
+	while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
+		if (de->attr & ATTR_DIR)
+			count++;
+	}
+	brelse(bh);
+	return count;
+}
+
+/*
+ * Scans a directory for a given file (name points to its formatted name).
+ * Returns an error code or zero.
+ */
+int fat_scan(struct inode *dir, const unsigned char *name,
+	     struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = dir->i_sb;
+
+	sinfo->slot_off = 0;
+	sinfo->bh = NULL;
+	while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
+				   &sinfo->de) >= 0) {
+		if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
+			sinfo->slot_off -= sizeof(*sinfo->de);
+			sinfo->nr_slots = 1;
+			sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+EXPORT_SYMBOL_GPL(fat_scan);
+
+/*
+ * Scans a directory for a given logstart.
+ * Returns an error code or zero.
+ */
+int fat_scan_logstart(struct inode *dir, int i_logstart,
+		      struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = dir->i_sb;
+
+	sinfo->slot_off = 0;
+	sinfo->bh = NULL;
+	while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
+				   &sinfo->de) >= 0) {
+		if (fat_get_start(MSDOS_SB(sb), sinfo->de) == i_logstart) {
+			sinfo->slot_off -= sizeof(*sinfo->de);
+			sinfo->nr_slots = 1;
+			sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+
+static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
+{
+	struct super_block *sb = dir->i_sb;
+	struct buffer_head *bh;
+	struct msdos_dir_entry *de, *endp;
+	int err = 0, orig_slots;
+
+	while (nr_slots) {
+		bh = NULL;
+		if (fat_get_entry(dir, &pos, &bh, &de) < 0) {
+			err = -EIO;
+			break;
+		}
+
+		orig_slots = nr_slots;
+		endp = (struct msdos_dir_entry *)(bh->b_data + sb->s_blocksize);
+		while (nr_slots && de < endp) {
+			de->name[0] = DELETED_FLAG;
+			de++;
+			nr_slots--;
+		}
+		mark_buffer_dirty_inode(bh, dir);
+		if (IS_DIRSYNC(dir))
+			err = sync_dirty_buffer(bh);
+		brelse(bh);
+		if (err)
+			break;
+
+		/* pos is *next* de's position, so this does `- sizeof(de)' */
+		pos += ((orig_slots - nr_slots) * sizeof(*de)) - sizeof(*de);
+	}
+
+	return err;
+}
+
+int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_dir_entry *de;
+	struct buffer_head *bh;
+	int err = 0, nr_slots;
+
+	/*
+	 * First stage: Remove the shortname. By this, the directory
+	 * entry is removed.
+	 */
+	nr_slots = sinfo->nr_slots;
+	de = sinfo->de;
+	sinfo->de = NULL;
+	bh = sinfo->bh;
+	sinfo->bh = NULL;
+	while (nr_slots && de >= (struct msdos_dir_entry *)bh->b_data) {
+		de->name[0] = DELETED_FLAG;
+		de--;
+		nr_slots--;
+	}
+	mark_buffer_dirty_inode(bh, dir);
+	if (IS_DIRSYNC(dir))
+		err = sync_dirty_buffer(bh);
+	brelse(bh);
+	if (err)
+		return err;
+	inode_inc_iversion(dir);
+
+	if (nr_slots) {
+		/*
+		 * Second stage: remove the remaining longname slots.
+		 * (This directory entry is already removed, and so return
+		 * the success)
+		 */
+		err = __fat_remove_entries(dir, sinfo->slot_off, nr_slots);
+		if (err) {
+			fat_msg(sb, KERN_WARNING,
+			       "Couldn't remove the long name slots");
+		}
+	}
+
+	fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
+	if (IS_DIRSYNC(dir))
+		(void)fat_sync_inode(dir);
+	else
+		mark_inode_dirty(dir);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_remove_entries);
+
+static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
+			      struct buffer_head **bhs, int nr_bhs)
+{
+	struct super_block *sb = dir->i_sb;
+	sector_t last_blknr = blknr + MSDOS_SB(sb)->sec_per_clus;
+	int err, i, n;
+
+	/* Zeroing the unused blocks on this cluster */
+	blknr += nr_used;
+	n = nr_used;
+	while (blknr < last_blknr) {
+		bhs[n] = sb_getblk(sb, blknr);
+		if (!bhs[n]) {
+			err = -ENOMEM;
+			goto error;
+		}
+		/* Avoid race with userspace read via bdev */
+		lock_buffer(bhs[n]);
+		memset(bhs[n]->b_data, 0, sb->s_blocksize);
+		set_buffer_uptodate(bhs[n]);
+		unlock_buffer(bhs[n]);
+		mark_buffer_dirty_inode(bhs[n], dir);
+
+		n++;
+		blknr++;
+		if (n == nr_bhs) {
+			if (IS_DIRSYNC(dir)) {
+				err = fat_sync_bhs(bhs, n);
+				if (err)
+					goto error;
+			}
+			for (i = 0; i < n; i++)
+				brelse(bhs[i]);
+			n = 0;
+		}
+	}
+	if (IS_DIRSYNC(dir)) {
+		err = fat_sync_bhs(bhs, n);
+		if (err)
+			goto error;
+	}
+	for (i = 0; i < n; i++)
+		brelse(bhs[i]);
+
+	return 0;
+
+error:
+	for (i = 0; i < n; i++)
+		bforget(bhs[i]);
+	return err;
+}
+
+int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	struct msdos_dir_entry *de;
+	sector_t blknr;
+	__le16 date, time;
+	u8 time_cs;
+	int err, cluster;
+
+	err = fat_alloc_clusters(dir, &cluster, 1);
+	if (err)
+		goto error;
+
+	blknr = fat_clus_to_blknr(sbi, cluster);
+	bhs[0] = sb_getblk(sb, blknr);
+	if (!bhs[0]) {
+		err = -ENOMEM;
+		goto error_free;
+	}
+
+	fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
+
+	de = (struct msdos_dir_entry *)bhs[0]->b_data;
+	/* Avoid race with userspace read via bdev */
+	lock_buffer(bhs[0]);
+	/* filling the new directory slots ("." and ".." entries) */
+	memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
+	memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
+	de->attr = de[1].attr = ATTR_DIR;
+	de[0].lcase = de[1].lcase = 0;
+	de[0].time = de[1].time = time;
+	de[0].date = de[1].date = date;
+	if (sbi->options.isvfat) {
+		/* extra timestamps */
+		de[0].ctime = de[1].ctime = time;
+		de[0].ctime_cs = de[1].ctime_cs = time_cs;
+		de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
+	} else {
+		de[0].ctime = de[1].ctime = 0;
+		de[0].ctime_cs = de[1].ctime_cs = 0;
+		de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
+	}
+	fat_set_start(&de[0], cluster);
+	fat_set_start(&de[1], MSDOS_I(dir)->i_logstart);
+	de[0].size = de[1].size = 0;
+	memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
+	set_buffer_uptodate(bhs[0]);
+	unlock_buffer(bhs[0]);
+	mark_buffer_dirty_inode(bhs[0], dir);
+
+	err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
+	if (err)
+		goto error_free;
+
+	return cluster;
+
+error_free:
+	fat_free_clusters(dir, cluster);
+error:
+	return err;
+}
+EXPORT_SYMBOL_GPL(fat_alloc_new_dir);
+
+static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
+			       int *nr_cluster, struct msdos_dir_entry **de,
+			       struct buffer_head **bh, loff_t *i_pos)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	sector_t blknr, start_blknr, last_blknr;
+	unsigned long size, copy;
+	int err, i, n, offset, cluster[2];
+
+	/*
+	 * The minimum cluster size is 512bytes, and maximum entry
+	 * size is 32*slots (672bytes).  So, iff the cluster size is
+	 * 512bytes, we may need two clusters.
+	 */
+	size = nr_slots * sizeof(struct msdos_dir_entry);
+	*nr_cluster = (size + (sbi->cluster_size - 1)) >> sbi->cluster_bits;
+	BUG_ON(*nr_cluster > 2);
+
+	err = fat_alloc_clusters(dir, cluster, *nr_cluster);
+	if (err)
+		goto error;
+
+	/*
+	 * First stage: Fill the directory entry.  NOTE: This cluster
+	 * is not referenced from any inode yet, so updates order is
+	 * not important.
+	 */
+	i = n = copy = 0;
+	do {
+		start_blknr = blknr = fat_clus_to_blknr(sbi, cluster[i]);
+		last_blknr = start_blknr + sbi->sec_per_clus;
+		while (blknr < last_blknr) {
+			bhs[n] = sb_getblk(sb, blknr);
+			if (!bhs[n]) {
+				err = -ENOMEM;
+				goto error_nomem;
+			}
+
+			/* fill the directory entry */
+			copy = min(size, sb->s_blocksize);
+			/* Avoid race with userspace read via bdev */
+			lock_buffer(bhs[n]);
+			memcpy(bhs[n]->b_data, slots, copy);
+			set_buffer_uptodate(bhs[n]);
+			unlock_buffer(bhs[n]);
+			mark_buffer_dirty_inode(bhs[n], dir);
+			slots += copy;
+			size -= copy;
+			if (!size)
+				break;
+			n++;
+			blknr++;
+		}
+	} while (++i < *nr_cluster);
+
+	memset(bhs[n]->b_data + copy, 0, sb->s_blocksize - copy);
+	offset = copy - sizeof(struct msdos_dir_entry);
+	get_bh(bhs[n]);
+	*bh = bhs[n];
+	*de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
+	*i_pos = fat_make_i_pos(sb, *bh, *de);
+
+	/* Second stage: clear the rest of cluster, and write outs */
+	err = fat_zeroed_cluster(dir, start_blknr, ++n, bhs, MAX_BUF_PER_PAGE);
+	if (err)
+		goto error_free;
+
+	return cluster[0];
+
+error_free:
+	brelse(*bh);
+	*bh = NULL;
+	n = 0;
+error_nomem:
+	for (i = 0; i < n; i++)
+		bforget(bhs[i]);
+	fat_free_clusters(dir, cluster[0]);
+error:
+	return err;
+}
+
+int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
+		    struct fat_slot_info *sinfo)
+{
+	struct super_block *sb = dir->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh, *prev, *bhs[3]; /* 32*slots (672bytes) */
+	struct msdos_dir_entry *de;
+	int err, free_slots, i, nr_bhs;
+	loff_t pos, i_pos;
+
+	sinfo->nr_slots = nr_slots;
+
+	/* First stage: search free directory entries */
+	free_slots = nr_bhs = 0;
+	bh = prev = NULL;
+	pos = 0;
+	err = -ENOSPC;
+	while (fat_get_entry(dir, &pos, &bh, &de) > -1) {
+		/* check the maximum size of directory */
+		if (pos >= FAT_MAX_DIR_SIZE)
+			goto error;
+
+		if (IS_FREE(de->name)) {
+			if (prev != bh) {
+				get_bh(bh);
+				bhs[nr_bhs] = prev = bh;
+				nr_bhs++;
+			}
+			free_slots++;
+			if (free_slots == nr_slots)
+				goto found;
+		} else {
+			for (i = 0; i < nr_bhs; i++)
+				brelse(bhs[i]);
+			prev = NULL;
+			free_slots = nr_bhs = 0;
+		}
+	}
+	if (dir->i_ino == MSDOS_ROOT_INO) {
+		if (!is_fat32(sbi))
+			goto error;
+	} else if (MSDOS_I(dir)->i_start == 0) {
+		fat_msg(sb, KERN_ERR, "Corrupted directory (i_pos %lld)",
+		       MSDOS_I(dir)->i_pos);
+		err = -EIO;
+		goto error;
+	}
+
+found:
+	err = 0;
+	pos -= free_slots * sizeof(*de);
+	nr_slots -= free_slots;
+	if (free_slots) {
+		/*
+		 * Second stage: filling the free entries with new entries.
+		 * NOTE: If this slots has shortname, first, we write
+		 * the long name slots, then write the short name.
+		 */
+		int size = free_slots * sizeof(*de);
+		int offset = pos & (sb->s_blocksize - 1);
+		int long_bhs = nr_bhs - (nr_slots == 0);
+
+		/* Fill the long name slots. */
+		for (i = 0; i < long_bhs; i++) {
+			int copy = min_t(int, sb->s_blocksize - offset, size);
+			memcpy(bhs[i]->b_data + offset, slots, copy);
+			mark_buffer_dirty_inode(bhs[i], dir);
+			offset = 0;
+			slots += copy;
+			size -= copy;
+		}
+		if (long_bhs && IS_DIRSYNC(dir))
+			err = fat_sync_bhs(bhs, long_bhs);
+		if (!err && i < nr_bhs) {
+			/* Fill the short name slot. */
+			int copy = min_t(int, sb->s_blocksize - offset, size);
+			memcpy(bhs[i]->b_data + offset, slots, copy);
+			mark_buffer_dirty_inode(bhs[i], dir);
+			if (IS_DIRSYNC(dir))
+				err = sync_dirty_buffer(bhs[i]);
+		}
+		for (i = 0; i < nr_bhs; i++)
+			brelse(bhs[i]);
+		if (err)
+			goto error_remove;
+	}
+
+	if (nr_slots) {
+		int cluster, nr_cluster;
+
+		/*
+		 * Third stage: allocate the cluster for new entries.
+		 * And initialize the cluster with new entries, then
+		 * add the cluster to dir.
+		 */
+		cluster = fat_add_new_entries(dir, slots, nr_slots, &nr_cluster,
+					      &de, &bh, &i_pos);
+		if (cluster < 0) {
+			err = cluster;
+			goto error_remove;
+		}
+		err = fat_chain_add(dir, cluster, nr_cluster);
+		if (err) {
+			fat_free_clusters(dir, cluster);
+			goto error_remove;
+		}
+		if (dir->i_size & (sbi->cluster_size - 1)) {
+			fat_fs_error(sb, "Odd directory size");
+			dir->i_size = (dir->i_size + sbi->cluster_size - 1)
+				& ~((loff_t)sbi->cluster_size - 1);
+		}
+		dir->i_size += nr_cluster << sbi->cluster_bits;
+		MSDOS_I(dir)->mmu_private += nr_cluster << sbi->cluster_bits;
+	}
+	sinfo->slot_off = pos;
+	sinfo->de = de;
+	sinfo->bh = bh;
+	sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
+
+	return 0;
+
+error:
+	brelse(bh);
+	for (i = 0; i < nr_bhs; i++)
+		brelse(bhs[i]);
+	return err;
+
+error_remove:
+	brelse(bh);
+	if (free_slots)
+		__fat_remove_entries(dir, pos, free_slots);
+	return err;
+}
+EXPORT_SYMBOL_GPL(fat_add_entries);
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
new file mode 100644
index 000000000..a415c02ed
--- /dev/null
+++ b/fs/fat/fat.h
@@ -0,0 +1,477 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _FAT_H
+#define _FAT_H
+
+#include <linux/buffer_head.h>
+#include <linux/nls.h>
+#include <linux/hash.h>
+#include <linux/ratelimit.h>
+#include <linux/msdos_fs.h>
+
+/*
+ * vfat shortname flags
+ */
+#define VFAT_SFN_DISPLAY_LOWER	0x0001 /* convert to lowercase for display */
+#define VFAT_SFN_DISPLAY_WIN95	0x0002 /* emulate win95 rule for display */
+#define VFAT_SFN_DISPLAY_WINNT	0x0004 /* emulate winnt rule for display */
+#define VFAT_SFN_CREATE_WIN95	0x0100 /* emulate win95 rule for create */
+#define VFAT_SFN_CREATE_WINNT	0x0200 /* emulate winnt rule for create */
+
+#define FAT_ERRORS_CONT		1      /* ignore error and continue */
+#define FAT_ERRORS_PANIC	2      /* panic on error */
+#define FAT_ERRORS_RO		3      /* remount r/o on error */
+
+#define FAT_NFS_STALE_RW	1      /* NFS RW support, can cause ESTALE */
+#define FAT_NFS_NOSTALE_RO	2      /* NFS RO support, no ESTALE issue */
+
+struct fat_mount_options {
+	kuid_t fs_uid;
+	kgid_t fs_gid;
+	unsigned short fs_fmask;
+	unsigned short fs_dmask;
+	unsigned short codepage;   /* Codepage for shortname conversions */
+	int time_offset;	   /* Offset of timestamps from UTC (in minutes) */
+	char *iocharset;           /* Charset used for filename input/display */
+	unsigned short shortname;  /* flags for shortname display/create rule */
+	unsigned char name_check;  /* r = relaxed, n = normal, s = strict */
+	unsigned char errors;	   /* On error: continue, panic, remount-ro */
+	unsigned char nfs;	  /* NFS support: nostale_ro, stale_rw */
+	unsigned short allow_utime;/* permission for setting the [am]time */
+	unsigned quiet:1,          /* set = fake successful chmods and chowns */
+		 showexec:1,       /* set = only set x bit for com/exe/bat */
+		 sys_immutable:1,  /* set = system files are immutable */
+		 dotsOK:1,         /* set = hidden and system files are named '.filename' */
+		 isvfat:1,         /* 0=no vfat long filename support, 1=vfat support */
+		 utf8:1,	   /* Use of UTF-8 character set (Default) */
+		 unicode_xlate:1,  /* create escape sequences for unhandled Unicode */
+		 numtail:1,        /* Does first alias have a numeric '~1' type tail? */
+		 flush:1,	   /* write things quickly */
+		 nocase:1,	   /* Does this need case conversion? 0=need case conversion*/
+		 usefree:1,	   /* Use free_clusters for FAT32 */
+		 tz_set:1,	   /* Filesystem timestamps' offset set */
+		 rodir:1,	   /* allow ATTR_RO for directory */
+		 discard:1,	   /* Issue discard requests on deletions */
+		 dos1xfloppy:1;	   /* Assume default BPB for DOS 1.x floppies */
+};
+
+#define FAT_HASH_BITS	8
+#define FAT_HASH_SIZE	(1UL << FAT_HASH_BITS)
+
+/*
+ * MS-DOS file system in-core superblock data
+ */
+struct msdos_sb_info {
+	unsigned short sec_per_clus;  /* sectors/cluster */
+	unsigned short cluster_bits;  /* log2(cluster_size) */
+	unsigned int cluster_size;    /* cluster size */
+	unsigned char fats, fat_bits; /* number of FATs, FAT bits (12,16 or 32) */
+	unsigned short fat_start;
+	unsigned long fat_length;     /* FAT start & length (sec.) */
+	unsigned long dir_start;
+	unsigned short dir_entries;   /* root dir start & entries */
+	unsigned long data_start;     /* first data sector */
+	unsigned long max_cluster;    /* maximum cluster number */
+	unsigned long root_cluster;   /* first cluster of the root directory */
+	unsigned long fsinfo_sector;  /* sector number of FAT32 fsinfo */
+	struct mutex fat_lock;
+	struct mutex nfs_build_inode_lock;
+	struct mutex s_lock;
+	unsigned int prev_free;      /* previously allocated cluster number */
+	unsigned int free_clusters;  /* -1 if undefined */
+	unsigned int free_clus_valid; /* is free_clusters valid? */
+	struct fat_mount_options options;
+	struct nls_table *nls_disk;   /* Codepage used on disk */
+	struct nls_table *nls_io;     /* Charset used for input and display */
+	const void *dir_ops;	      /* Opaque; default directory operations */
+	int dir_per_block;	      /* dir entries per block */
+	int dir_per_block_bits;	      /* log2(dir_per_block) */
+	unsigned int vol_id;		/*volume ID*/
+
+	int fatent_shift;
+	const struct fatent_operations *fatent_ops;
+	struct inode *fat_inode;
+	struct inode *fsinfo_inode;
+
+	struct ratelimit_state ratelimit;
+
+	spinlock_t inode_hash_lock;
+	struct hlist_head inode_hashtable[FAT_HASH_SIZE];
+
+	spinlock_t dir_hash_lock;
+	struct hlist_head dir_hashtable[FAT_HASH_SIZE];
+
+	unsigned int dirty;           /* fs state before mount */
+	struct rcu_head rcu;
+};
+
+#define FAT_CACHE_VALID	0	/* special case for valid cache */
+
+/*
+ * MS-DOS file system inode data in memory
+ */
+struct msdos_inode_info {
+	spinlock_t cache_lru_lock;
+	struct list_head cache_lru;
+	int nr_caches;
+	/* for avoiding the race between fat_free() and fat_get_cluster() */
+	unsigned int cache_valid_id;
+
+	/* NOTE: mmu_private is 64bits, so must hold ->i_mutex to access */
+	loff_t mmu_private;	/* physically allocated size */
+
+	int i_start;		/* first cluster or 0 */
+	int i_logstart;		/* logical first cluster */
+	int i_attrs;		/* unused attribute bits */
+	loff_t i_pos;		/* on-disk position of directory entry or 0 */
+	struct hlist_node i_fat_hash;	/* hash by i_location */
+	struct hlist_node i_dir_hash;	/* hash by i_logstart */
+	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
+	struct timespec64 i_crtime;	/* File creation (birth) time */
+	struct inode vfs_inode;
+};
+
+struct fat_slot_info {
+	loff_t i_pos;		/* on-disk position of directory entry */
+	loff_t slot_off;	/* offset for slot or de start */
+	int nr_slots;		/* number of slots + 1(de) in filename */
+	struct msdos_dir_entry *de;
+	struct buffer_head *bh;
+};
+
+static inline struct msdos_sb_info *MSDOS_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+/*
+ * Functions that determine the variant of the FAT file system (i.e.,
+ * whether this is FAT12, FAT16 or FAT32.
+ */
+static inline bool is_fat12(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 12;
+}
+
+static inline bool is_fat16(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 16;
+}
+
+static inline bool is_fat32(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 32;
+}
+
+/* Maximum number of clusters */
+static inline u32 max_fat(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	return is_fat32(sbi) ? MAX_FAT32 :
+		is_fat16(sbi) ? MAX_FAT16 : MAX_FAT12;
+}
+
+static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
+{
+	return container_of(inode, struct msdos_inode_info, vfs_inode);
+}
+
+/*
+ * If ->i_mode can't hold S_IWUGO (i.e. ATTR_RO), we use ->i_attrs to
+ * save ATTR_RO instead of ->i_mode.
+ *
+ * If it's directory and !sbi->options.rodir, ATTR_RO isn't read-only
+ * bit, it's just used as flag for app.
+ */
+static inline int fat_mode_can_hold_ro(struct inode *inode)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	umode_t mask;
+
+	if (S_ISDIR(inode->i_mode)) {
+		if (!sbi->options.rodir)
+			return 0;
+		mask = ~sbi->options.fs_dmask;
+	} else
+		mask = ~sbi->options.fs_fmask;
+
+	if (!(mask & S_IWUGO))
+		return 0;
+	return 1;
+}
+
+/* Convert attribute bits and a mask to the UNIX mode. */
+static inline umode_t fat_make_mode(struct msdos_sb_info *sbi,
+				   u8 attrs, umode_t mode)
+{
+	if (attrs & ATTR_RO && !((attrs & ATTR_DIR) && !sbi->options.rodir))
+		mode &= ~S_IWUGO;
+
+	if (attrs & ATTR_DIR)
+		return (mode & ~sbi->options.fs_dmask) | S_IFDIR;
+	else
+		return (mode & ~sbi->options.fs_fmask) | S_IFREG;
+}
+
+/* Return the FAT attribute byte for this inode */
+static inline u8 fat_make_attrs(struct inode *inode)
+{
+	u8 attrs = MSDOS_I(inode)->i_attrs;
+	if (S_ISDIR(inode->i_mode))
+		attrs |= ATTR_DIR;
+	if (fat_mode_can_hold_ro(inode) && !(inode->i_mode & S_IWUGO))
+		attrs |= ATTR_RO;
+	return attrs;
+}
+
+static inline void fat_save_attrs(struct inode *inode, u8 attrs)
+{
+	if (fat_mode_can_hold_ro(inode))
+		MSDOS_I(inode)->i_attrs = attrs & ATTR_UNUSED;
+	else
+		MSDOS_I(inode)->i_attrs = attrs & (ATTR_UNUSED | ATTR_RO);
+}
+
+static inline unsigned char fat_checksum(const __u8 *name)
+{
+	unsigned char s = name[0];
+	s = (s<<7) + (s>>1) + name[1];	s = (s<<7) + (s>>1) + name[2];
+	s = (s<<7) + (s>>1) + name[3];	s = (s<<7) + (s>>1) + name[4];
+	s = (s<<7) + (s>>1) + name[5];	s = (s<<7) + (s>>1) + name[6];
+	s = (s<<7) + (s>>1) + name[7];	s = (s<<7) + (s>>1) + name[8];
+	s = (s<<7) + (s>>1) + name[9];	s = (s<<7) + (s>>1) + name[10];
+	return s;
+}
+
+static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus)
+{
+	return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus
+		+ sbi->data_start;
+}
+
+static inline void fat_get_blknr_offset(struct msdos_sb_info *sbi,
+				loff_t i_pos, sector_t *blknr, int *offset)
+{
+	*blknr = i_pos >> sbi->dir_per_block_bits;
+	*offset = i_pos & (sbi->dir_per_block - 1);
+}
+
+static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
+					struct inode *inode)
+{
+	loff_t i_pos;
+#if BITS_PER_LONG == 32
+	spin_lock(&sbi->inode_hash_lock);
+#endif
+	i_pos = MSDOS_I(inode)->i_pos;
+#if BITS_PER_LONG == 32
+	spin_unlock(&sbi->inode_hash_lock);
+#endif
+	return i_pos;
+}
+
+static inline void fat16_towchar(wchar_t *dst, const __u8 *src, size_t len)
+{
+#ifdef __BIG_ENDIAN
+	while (len--) {
+		*dst++ = src[0] | (src[1] << 8);
+		src += 2;
+	}
+#else
+	memcpy(dst, src, len * 2);
+#endif
+}
+
+static inline int fat_get_start(const struct msdos_sb_info *sbi,
+				const struct msdos_dir_entry *de)
+{
+	int cluster = le16_to_cpu(de->start);
+	if (is_fat32(sbi))
+		cluster |= (le16_to_cpu(de->starthi) << 16);
+	return cluster;
+}
+
+static inline void fat_set_start(struct msdos_dir_entry *de, int cluster)
+{
+	de->start   = cpu_to_le16(cluster);
+	de->starthi = cpu_to_le16(cluster >> 16);
+}
+
+static inline void fatwchar_to16(__u8 *dst, const wchar_t *src, size_t len)
+{
+#ifdef __BIG_ENDIAN
+	while (len--) {
+		dst[0] = *src & 0x00FF;
+		dst[1] = (*src & 0xFF00) >> 8;
+		dst += 2;
+		src++;
+	}
+#else
+	memcpy(dst, src, len * 2);
+#endif
+}
+
+/* fat/cache.c */
+extern void fat_cache_inval_inode(struct inode *inode);
+extern int fat_get_cluster(struct inode *inode, int cluster,
+			   int *fclus, int *dclus);
+extern int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
+				  sector_t last_block,
+				  unsigned long *mapped_blocks, sector_t *bmap);
+extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
+		    unsigned long *mapped_blocks, int create, bool from_bmap);
+
+/* fat/dir.c */
+extern const struct file_operations fat_dir_operations;
+extern int fat_search_long(struct inode *inode, const unsigned char *name,
+			   int name_len, struct fat_slot_info *sinfo);
+extern int fat_dir_empty(struct inode *dir);
+extern int fat_subdirs(struct inode *dir);
+extern int fat_scan(struct inode *dir, const unsigned char *name,
+		    struct fat_slot_info *sinfo);
+extern int fat_scan_logstart(struct inode *dir, int i_logstart,
+			     struct fat_slot_info *sinfo);
+extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
+				struct msdos_dir_entry **de);
+extern int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts);
+extern int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
+			   struct fat_slot_info *sinfo);
+extern int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo);
+
+/* fat/fatent.c */
+struct fat_entry {
+	int entry;
+	union {
+		u8 *ent12_p[2];
+		__le16 *ent16_p;
+		__le32 *ent32_p;
+	} u;
+	int nr_bhs;
+	struct buffer_head *bhs[2];
+	struct inode *fat_inode;
+};
+
+static inline void fatent_init(struct fat_entry *fatent)
+{
+	fatent->nr_bhs = 0;
+	fatent->entry = 0;
+	fatent->u.ent32_p = NULL;
+	fatent->bhs[0] = fatent->bhs[1] = NULL;
+	fatent->fat_inode = NULL;
+}
+
+static inline void fatent_set_entry(struct fat_entry *fatent, int entry)
+{
+	fatent->entry = entry;
+	fatent->u.ent32_p = NULL;
+}
+
+static inline void fatent_brelse(struct fat_entry *fatent)
+{
+	int i;
+	fatent->u.ent32_p = NULL;
+	for (i = 0; i < fatent->nr_bhs; i++)
+		brelse(fatent->bhs[i]);
+	fatent->nr_bhs = 0;
+	fatent->bhs[0] = fatent->bhs[1] = NULL;
+	fatent->fat_inode = NULL;
+}
+
+static inline bool fat_valid_entry(struct msdos_sb_info *sbi, int entry)
+{
+	return FAT_START_ENT <= entry && entry < sbi->max_cluster;
+}
+
+extern void fat_ent_access_init(struct super_block *sb);
+extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent,
+			int entry);
+extern int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
+			 int new, int wait);
+extern int fat_alloc_clusters(struct inode *inode, int *cluster,
+			      int nr_cluster);
+extern int fat_free_clusters(struct inode *inode, int cluster);
+extern int fat_count_free_clusters(struct super_block *sb);
+extern int fat_trim_fs(struct inode *inode, struct fstrim_range *range);
+
+/* fat/file.c */
+extern long fat_generic_ioctl(struct file *filp, unsigned int cmd,
+			      unsigned long arg);
+extern const struct file_operations fat_file_operations;
+extern const struct inode_operations fat_file_inode_operations;
+extern int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		       struct iattr *attr);
+extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
+extern int fat_getattr(struct user_namespace *mnt_userns,
+		       const struct path *path, struct kstat *stat,
+		       u32 request_mask, unsigned int flags);
+extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
+			  int datasync);
+
+/* fat/inode.c */
+extern int fat_block_truncate_page(struct inode *inode, loff_t from);
+extern void fat_attach(struct inode *inode, loff_t i_pos);
+extern void fat_detach(struct inode *inode);
+extern struct inode *fat_iget(struct super_block *sb, loff_t i_pos);
+extern struct inode *fat_build_inode(struct super_block *sb,
+			struct msdos_dir_entry *de, loff_t i_pos);
+extern int fat_sync_inode(struct inode *inode);
+extern int fat_fill_super(struct super_block *sb, void *data, int silent,
+			  int isvfat, void (*setup)(struct super_block *));
+extern int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de);
+
+extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
+			    struct inode *i2);
+static inline unsigned long fat_dir_hash(int logstart)
+{
+	return hash_32(logstart, FAT_HASH_BITS);
+}
+extern int fat_add_cluster(struct inode *inode);
+
+/* fat/misc.c */
+extern __printf(3, 4) __cold
+void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...);
+#define fat_fs_error(sb, fmt, args...)		\
+	__fat_fs_error(sb, 1, fmt , ## args)
+#define fat_fs_error_ratelimit(sb, fmt, args...) \
+	__fat_fs_error(sb, __ratelimit(&MSDOS_SB(sb)->ratelimit), fmt , ## args)
+
+#define FAT_PRINTK_PREFIX "%sFAT-fs (%s): "
+#define fat_msg(sb, level, fmt, args...)				\
+do {									\
+	printk_index_subsys_emit(FAT_PRINTK_PREFIX, level, fmt, ##args);\
+	_fat_msg(sb, level, fmt, ##args);				\
+} while (0)
+__printf(3, 4) __cold
+void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...);
+#define fat_msg_ratelimit(sb, level, fmt, args...)	\
+	do {	\
+			if (__ratelimit(&MSDOS_SB(sb)->ratelimit))	\
+				fat_msg(sb, level, fmt, ## args);	\
+	 } while (0)
+extern int fat_clusters_flush(struct super_block *sb);
+extern int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster);
+extern void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			      __le16 __time, __le16 __date, u8 time_cs);
+extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			      __le16 *time, __le16 *date, u8 *time_cs);
+extern struct timespec64 fat_truncate_atime(const struct msdos_sb_info *sbi,
+					    const struct timespec64 *ts);
+extern struct timespec64 fat_truncate_mtime(const struct msdos_sb_info *sbi,
+					    const struct timespec64 *ts);
+extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
+			     int flags);
+extern int fat_update_time(struct inode *inode, struct timespec64 *now,
+			   int flags);
+extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
+
+int fat_cache_init(void);
+void fat_cache_destroy(void);
+
+/* fat/nfs.c */
+extern const struct export_operations fat_export_ops;
+extern const struct export_operations fat_export_ops_nostale;
+
+/* helper for printk */
+typedef unsigned long long	llu;
+
+#endif /* !_FAT_H */
diff --git a/fs/fat/fat_test.c b/fs/fat/fat_test.c
new file mode 100644
index 000000000..2dab4ca1d
--- /dev/null
+++ b/fs/fat/fat_test.c
@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for FAT filesystems.
+ *
+ * Copyright (C) 2020 Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#include <kunit/test.h>
+
+#include "fat.h"
+
+static void fat_checksum_test(struct kunit *test)
+{
+	/* With no extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("VMLINUX    "), (u8)44);
+	/* With 3-letter extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("README  TXT"), (u8)115);
+	/* With short (1-letter) extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("ABCDEFGHA  "), (u8)98);
+}
+
+struct fat_timestamp_testcase {
+	const char *name;
+	struct timespec64 ts;
+	__le16 time;
+	__le16 date;
+	u8 cs;
+	int time_offset;
+};
+
+static struct fat_timestamp_testcase time_test_cases[] = {
+	{
+		.name = "Earliest possible UTC (1980-01-01 00:00:00)",
+		.ts = {.tv_sec = 315532800LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Latest possible UTC (2107-12-31 23:59:58)",
+		.ts = {.tv_sec = 4354819198LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Earliest possible (UTC-11) (== 1979-12-31 13:00:00 UTC)",
+		.ts = {.tv_sec = 315493200LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = 11 * 60,
+	},
+	{
+		.name = "Latest possible (UTC+11) (== 2108-01-01 10:59:58 UTC)",
+		.ts = {.tv_sec = 4354858798LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 0,
+		.time_offset = -11 * 60,
+	},
+	{
+		.name = "Leap Day / Year (1996-02-29 00:00:00)",
+		.ts = {.tv_sec = 825552000LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(8285),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Year 2000 is leap year (2000-02-29 00:00:00)",
+		.ts = {.tv_sec = 951782400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(10333),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Year 2100 not leap year (2100-03-01 00:00:00)",
+		.ts = {.tv_sec = 4107542400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(61537),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Leap year + timezone UTC+1 (== 2004-02-29 00:30:00 UTC)",
+		.ts = {.tv_sec = 1078014600LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(48064),
+		.date = cpu_to_le16(12380),
+		.cs = 0,
+		.time_offset = -60,
+	},
+	{
+		.name = "Leap year + timezone UTC-1 (== 2004-02-29 23:30:00 UTC)",
+		.ts = {.tv_sec = 1078097400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(960),
+		.date = cpu_to_le16(12385),
+		.cs = 0,
+		.time_offset = 60,
+	},
+	{
+		.name = "VFAT odd-second resolution (1999-12-31 23:59:59)",
+		.ts = {.tv_sec = 946684799LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(10143),
+		.cs = 100,
+		.time_offset = 0,
+	},
+	{
+		.name = "VFAT 10ms resolution (1980-01-01 00:00:00:0010)",
+		.ts = {.tv_sec = 315532800LL, .tv_nsec = 10000000L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 1,
+		.time_offset = 0,
+	},
+};
+
+static void time_testcase_desc(struct fat_timestamp_testcase *t,
+			       char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(fat_time, time_test_cases, time_testcase_desc);
+
+static void fat_time_fat2unix_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	struct timespec64 ts;
+	struct fat_timestamp_testcase *testcase =
+		(struct fat_timestamp_testcase *)test->param_value;
+
+	fake_sb.options.tz_set = 1;
+	fake_sb.options.time_offset = testcase->time_offset;
+
+	fat_time_fat2unix(&fake_sb, &ts,
+			  testcase->time,
+			  testcase->date,
+			  testcase->cs);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->ts.tv_sec,
+			    ts.tv_sec,
+			    "Timestamp mismatch (seconds)\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->ts.tv_nsec,
+			    ts.tv_nsec,
+			    "Timestamp mismatch (nanoseconds)\n");
+}
+
+static void fat_time_unix2fat_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	__le16 date, time;
+	u8 cs;
+	struct fat_timestamp_testcase *testcase =
+		(struct fat_timestamp_testcase *)test->param_value;
+
+	fake_sb.options.tz_set = 1;
+	fake_sb.options.time_offset = testcase->time_offset;
+
+	fat_time_unix2fat(&fake_sb, &testcase->ts,
+			  &time, &date, &cs);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    le16_to_cpu(testcase->time),
+			    le16_to_cpu(time),
+			    "Time mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    le16_to_cpu(testcase->date),
+			    le16_to_cpu(date),
+			    "Date mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->cs,
+			    cs,
+			    "Centisecond mismatch\n");
+}
+
+static struct kunit_case fat_test_cases[] = {
+	KUNIT_CASE(fat_checksum_test),
+	KUNIT_CASE_PARAM(fat_time_fat2unix_test, fat_time_gen_params),
+	KUNIT_CASE_PARAM(fat_time_unix2fat_test, fat_time_gen_params),
+	{},
+};
+
+static struct kunit_suite fat_test_suite = {
+	.name = "fat_test",
+	.test_cases = fat_test_cases,
+};
+
+kunit_test_suites(&fat_test_suite);
+
+MODULE_LICENSE("GPL v2");
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
new file mode 100644
index 000000000..1db348f8f
--- /dev/null
+++ b/fs/fat/fatent.c
@@ -0,0 +1,848 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2004, OGAWA Hirofumi
+ */
+
+#include <linux/blkdev.h>
+#include <linux/sched/signal.h>
+#include <linux/backing-dev-defs.h>
+#include "fat.h"
+
+struct fatent_operations {
+	void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
+	void (*ent_set_ptr)(struct fat_entry *, int);
+	int (*ent_bread)(struct super_block *, struct fat_entry *,
+			 int, sector_t);
+	int (*ent_get)(struct fat_entry *);
+	void (*ent_put)(struct fat_entry *, int);
+	int (*ent_next)(struct fat_entry *);
+};
+
+static DEFINE_SPINLOCK(fat12_entry_lock);
+
+static void fat12_ent_blocknr(struct super_block *sb, int entry,
+			      int *offset, sector_t *blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int bytes = entry + (entry >> 1);
+	WARN_ON(!fat_valid_entry(sbi, entry));
+	*offset = bytes & (sb->s_blocksize - 1);
+	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
+}
+
+static void fat_ent_blocknr(struct super_block *sb, int entry,
+			    int *offset, sector_t *blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int bytes = (entry << sbi->fatent_shift);
+	WARN_ON(!fat_valid_entry(sbi, entry));
+	*offset = bytes & (sb->s_blocksize - 1);
+	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
+}
+
+static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	struct buffer_head **bhs = fatent->bhs;
+	if (fatent->nr_bhs == 1) {
+		WARN_ON(offset >= (bhs[0]->b_size - 1));
+		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
+		fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
+	} else {
+		WARN_ON(offset != (bhs[0]->b_size - 1));
+		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
+		fatent->u.ent12_p[1] = bhs[1]->b_data;
+	}
+}
+
+static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	WARN_ON(offset & (2 - 1));
+	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
+}
+
+static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	WARN_ON(offset & (4 - 1));
+	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
+}
+
+static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
+			   int offset, sector_t blocknr)
+{
+	struct buffer_head **bhs = fatent->bhs;
+
+	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
+	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
+
+	bhs[0] = sb_bread(sb, blocknr);
+	if (!bhs[0])
+		goto err;
+
+	if ((offset + 1) < sb->s_blocksize)
+		fatent->nr_bhs = 1;
+	else {
+		/* This entry is block boundary, it needs the next block */
+		blocknr++;
+		bhs[1] = sb_bread(sb, blocknr);
+		if (!bhs[1])
+			goto err_brelse;
+		fatent->nr_bhs = 2;
+	}
+	fat12_ent_set_ptr(fatent, offset);
+	return 0;
+
+err_brelse:
+	brelse(bhs[0]);
+err:
+	fat_msg_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
+			  (llu)blocknr);
+	return -EIO;
+}
+
+static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
+			 int offset, sector_t blocknr)
+{
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+
+	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
+	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
+	fatent->bhs[0] = sb_bread(sb, blocknr);
+	if (!fatent->bhs[0]) {
+		fat_msg_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
+				  (llu)blocknr);
+		return -EIO;
+	}
+	fatent->nr_bhs = 1;
+	ops->ent_set_ptr(fatent, offset);
+	return 0;
+}
+
+static int fat12_ent_get(struct fat_entry *fatent)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+	int next;
+
+	spin_lock(&fat12_entry_lock);
+	if (fatent->entry & 1)
+		next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
+	else
+		next = (*ent12_p[1] << 8) | *ent12_p[0];
+	spin_unlock(&fat12_entry_lock);
+
+	next &= 0x0fff;
+	if (next >= BAD_FAT12)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static int fat16_ent_get(struct fat_entry *fatent)
+{
+	int next = le16_to_cpu(*fatent->u.ent16_p);
+	WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
+	if (next >= BAD_FAT16)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static int fat32_ent_get(struct fat_entry *fatent)
+{
+	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
+	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
+	if (next >= BAD_FAT32)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static void fat12_ent_put(struct fat_entry *fatent, int new)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+
+	if (new == FAT_ENT_EOF)
+		new = EOF_FAT12;
+
+	spin_lock(&fat12_entry_lock);
+	if (fatent->entry & 1) {
+		*ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
+		*ent12_p[1] = new >> 4;
+	} else {
+		*ent12_p[0] = new & 0xff;
+		*ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
+	}
+	spin_unlock(&fat12_entry_lock);
+
+	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
+	if (fatent->nr_bhs == 2)
+		mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
+}
+
+static void fat16_ent_put(struct fat_entry *fatent, int new)
+{
+	if (new == FAT_ENT_EOF)
+		new = EOF_FAT16;
+
+	*fatent->u.ent16_p = cpu_to_le16(new);
+	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
+}
+
+static void fat32_ent_put(struct fat_entry *fatent, int new)
+{
+	WARN_ON(new & 0xf0000000);
+	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
+	*fatent->u.ent32_p = cpu_to_le32(new);
+	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
+}
+
+static int fat12_ent_next(struct fat_entry *fatent)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+	struct buffer_head **bhs = fatent->bhs;
+	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
+
+	fatent->entry++;
+	if (fatent->nr_bhs == 1) {
+		WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 2)));
+		WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 1)));
+		if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
+			ent12_p[0] = nextp - 1;
+			ent12_p[1] = nextp;
+			return 1;
+		}
+	} else {
+		WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 1)));
+		WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
+		ent12_p[0] = nextp - 1;
+		ent12_p[1] = nextp;
+		brelse(bhs[0]);
+		bhs[0] = bhs[1];
+		fatent->nr_bhs = 1;
+		return 1;
+	}
+	ent12_p[0] = NULL;
+	ent12_p[1] = NULL;
+	return 0;
+}
+
+static int fat16_ent_next(struct fat_entry *fatent)
+{
+	const struct buffer_head *bh = fatent->bhs[0];
+	fatent->entry++;
+	if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
+		fatent->u.ent16_p++;
+		return 1;
+	}
+	fatent->u.ent16_p = NULL;
+	return 0;
+}
+
+static int fat32_ent_next(struct fat_entry *fatent)
+{
+	const struct buffer_head *bh = fatent->bhs[0];
+	fatent->entry++;
+	if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
+		fatent->u.ent32_p++;
+		return 1;
+	}
+	fatent->u.ent32_p = NULL;
+	return 0;
+}
+
+static const struct fatent_operations fat12_ops = {
+	.ent_blocknr	= fat12_ent_blocknr,
+	.ent_set_ptr	= fat12_ent_set_ptr,
+	.ent_bread	= fat12_ent_bread,
+	.ent_get	= fat12_ent_get,
+	.ent_put	= fat12_ent_put,
+	.ent_next	= fat12_ent_next,
+};
+
+static const struct fatent_operations fat16_ops = {
+	.ent_blocknr	= fat_ent_blocknr,
+	.ent_set_ptr	= fat16_ent_set_ptr,
+	.ent_bread	= fat_ent_bread,
+	.ent_get	= fat16_ent_get,
+	.ent_put	= fat16_ent_put,
+	.ent_next	= fat16_ent_next,
+};
+
+static const struct fatent_operations fat32_ops = {
+	.ent_blocknr	= fat_ent_blocknr,
+	.ent_set_ptr	= fat32_ent_set_ptr,
+	.ent_bread	= fat_ent_bread,
+	.ent_get	= fat32_ent_get,
+	.ent_put	= fat32_ent_put,
+	.ent_next	= fat32_ent_next,
+};
+
+static inline void lock_fat(struct msdos_sb_info *sbi)
+{
+	mutex_lock(&sbi->fat_lock);
+}
+
+static inline void unlock_fat(struct msdos_sb_info *sbi)
+{
+	mutex_unlock(&sbi->fat_lock);
+}
+
+void fat_ent_access_init(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	mutex_init(&sbi->fat_lock);
+
+	if (is_fat32(sbi)) {
+		sbi->fatent_shift = 2;
+		sbi->fatent_ops = &fat32_ops;
+	} else if (is_fat16(sbi)) {
+		sbi->fatent_shift = 1;
+		sbi->fatent_ops = &fat16_ops;
+	} else if (is_fat12(sbi)) {
+		sbi->fatent_shift = -1;
+		sbi->fatent_ops = &fat12_ops;
+	} else {
+		fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
+	}
+}
+
+static void mark_fsinfo_dirty(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (sb_rdonly(sb) || !is_fat32(sbi))
+		return;
+
+	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
+}
+
+static inline int fat_ent_update_ptr(struct super_block *sb,
+				     struct fat_entry *fatent,
+				     int offset, sector_t blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct buffer_head **bhs = fatent->bhs;
+
+	/* Is this fatent's blocks including this entry? */
+	if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
+		return 0;
+	if (is_fat12(sbi)) {
+		if ((offset + 1) < sb->s_blocksize) {
+			/* This entry is on bhs[0]. */
+			if (fatent->nr_bhs == 2) {
+				brelse(bhs[1]);
+				fatent->nr_bhs = 1;
+			}
+		} else {
+			/* This entry needs the next block. */
+			if (fatent->nr_bhs != 2)
+				return 0;
+			if (bhs[1]->b_blocknr != (blocknr + 1))
+				return 0;
+		}
+	}
+	ops->ent_set_ptr(fatent, offset);
+	return 1;
+}
+
+int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	int err, offset;
+	sector_t blocknr;
+
+	if (!fat_valid_entry(sbi, entry)) {
+		fatent_brelse(fatent);
+		fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
+		return -EIO;
+	}
+
+	fatent_set_entry(fatent, entry);
+	ops->ent_blocknr(sb, entry, &offset, &blocknr);
+
+	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
+		fatent_brelse(fatent);
+		err = ops->ent_bread(sb, fatent, offset, blocknr);
+		if (err)
+			return err;
+	}
+	return ops->ent_get(fatent);
+}
+
+/* FIXME: We can write the blocks as more big chunk. */
+static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
+			  int nr_bhs)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *c_bh;
+	int err, n, copy;
+
+	err = 0;
+	for (copy = 1; copy < sbi->fats; copy++) {
+		sector_t backup_fat = sbi->fat_length * copy;
+
+		for (n = 0; n < nr_bhs; n++) {
+			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
+			if (!c_bh) {
+				err = -ENOMEM;
+				goto error;
+			}
+			/* Avoid race with userspace read via bdev */
+			lock_buffer(c_bh);
+			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
+			set_buffer_uptodate(c_bh);
+			unlock_buffer(c_bh);
+			mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
+			if (sb->s_flags & SB_SYNCHRONOUS)
+				err = sync_dirty_buffer(c_bh);
+			brelse(c_bh);
+			if (err)
+				goto error;
+		}
+	}
+error:
+	return err;
+}
+
+int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
+		  int new, int wait)
+{
+	struct super_block *sb = inode->i_sb;
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+	int err;
+
+	ops->ent_put(fatent, new);
+	if (wait) {
+		err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
+		if (err)
+			return err;
+	}
+	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
+}
+
+static inline int fat_ent_next(struct msdos_sb_info *sbi,
+			       struct fat_entry *fatent)
+{
+	if (sbi->fatent_ops->ent_next(fatent)) {
+		if (fatent->entry < sbi->max_cluster)
+			return 1;
+	}
+	return 0;
+}
+
+static inline int fat_ent_read_block(struct super_block *sb,
+				     struct fat_entry *fatent)
+{
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+	sector_t blocknr;
+	int offset;
+
+	fatent_brelse(fatent);
+	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+	return ops->ent_bread(sb, fatent, offset, blocknr);
+}
+
+static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
+			    struct fat_entry *fatent)
+{
+	int n, i;
+
+	for (n = 0; n < fatent->nr_bhs; n++) {
+		for (i = 0; i < *nr_bhs; i++) {
+			if (fatent->bhs[n] == bhs[i])
+				break;
+		}
+		if (i == *nr_bhs) {
+			get_bh(fatent->bhs[n]);
+			bhs[i] = fatent->bhs[n];
+			(*nr_bhs)++;
+		}
+	}
+}
+
+int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent, prev_ent;
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	int i, count, err, nr_bhs, idx_clus;
+
+	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));	/* fixed limit */
+
+	lock_fat(sbi);
+	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
+	    sbi->free_clusters < nr_cluster) {
+		unlock_fat(sbi);
+		return -ENOSPC;
+	}
+
+	err = nr_bhs = idx_clus = 0;
+	count = FAT_START_ENT;
+	fatent_init(&prev_ent);
+	fatent_init(&fatent);
+	fatent_set_entry(&fatent, sbi->prev_free + 1);
+	while (count < sbi->max_cluster) {
+		if (fatent.entry >= sbi->max_cluster)
+			fatent.entry = FAT_START_ENT;
+		fatent_set_entry(&fatent, fatent.entry);
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto out;
+
+		/* Find the free entries in a block */
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
+				int entry = fatent.entry;
+
+				/* make the cluster chain */
+				ops->ent_put(&fatent, FAT_ENT_EOF);
+				if (prev_ent.nr_bhs)
+					ops->ent_put(&prev_ent, entry);
+
+				fat_collect_bhs(bhs, &nr_bhs, &fatent);
+
+				sbi->prev_free = entry;
+				if (sbi->free_clusters != -1)
+					sbi->free_clusters--;
+
+				cluster[idx_clus] = entry;
+				idx_clus++;
+				if (idx_clus == nr_cluster)
+					goto out;
+
+				/*
+				 * fat_collect_bhs() gets ref-count of bhs,
+				 * so we can still use the prev_ent.
+				 */
+				prev_ent = fatent;
+			}
+			count++;
+			if (count == sbi->max_cluster)
+				break;
+		} while (fat_ent_next(sbi, &fatent));
+	}
+
+	/* Couldn't allocate the free entries */
+	sbi->free_clusters = 0;
+	sbi->free_clus_valid = 1;
+	err = -ENOSPC;
+
+out:
+	unlock_fat(sbi);
+	mark_fsinfo_dirty(sb);
+	fatent_brelse(&fatent);
+	if (!err) {
+		if (inode_needs_sync(inode))
+			err = fat_sync_bhs(bhs, nr_bhs);
+		if (!err)
+			err = fat_mirror_bhs(sb, bhs, nr_bhs);
+	}
+	for (i = 0; i < nr_bhs; i++)
+		brelse(bhs[i]);
+
+	if (err && idx_clus)
+		fat_free_clusters(inode, cluster[0]);
+
+	return err;
+}
+
+int fat_free_clusters(struct inode *inode, int cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	int i, err, nr_bhs;
+	int first_cl = cluster, dirty_fsinfo = 0;
+
+	nr_bhs = 0;
+	fatent_init(&fatent);
+	lock_fat(sbi);
+	do {
+		cluster = fat_ent_read(inode, &fatent, cluster);
+		if (cluster < 0) {
+			err = cluster;
+			goto error;
+		} else if (cluster == FAT_ENT_FREE) {
+			fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
+				     __func__);
+			err = -EIO;
+			goto error;
+		}
+
+		if (sbi->options.discard) {
+			/*
+			 * Issue discard for the sectors we no longer
+			 * care about, batching contiguous clusters
+			 * into one request
+			 */
+			if (cluster != fatent.entry + 1) {
+				int nr_clus = fatent.entry - first_cl + 1;
+
+				sb_issue_discard(sb,
+					fat_clus_to_blknr(sbi, first_cl),
+					nr_clus * sbi->sec_per_clus,
+					GFP_NOFS, 0);
+
+				first_cl = cluster;
+			}
+		}
+
+		ops->ent_put(&fatent, FAT_ENT_FREE);
+		if (sbi->free_clusters != -1) {
+			sbi->free_clusters++;
+			dirty_fsinfo = 1;
+		}
+
+		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
+			if (sb->s_flags & SB_SYNCHRONOUS) {
+				err = fat_sync_bhs(bhs, nr_bhs);
+				if (err)
+					goto error;
+			}
+			err = fat_mirror_bhs(sb, bhs, nr_bhs);
+			if (err)
+				goto error;
+			for (i = 0; i < nr_bhs; i++)
+				brelse(bhs[i]);
+			nr_bhs = 0;
+		}
+		fat_collect_bhs(bhs, &nr_bhs, &fatent);
+	} while (cluster != FAT_ENT_EOF);
+
+	if (sb->s_flags & SB_SYNCHRONOUS) {
+		err = fat_sync_bhs(bhs, nr_bhs);
+		if (err)
+			goto error;
+	}
+	err = fat_mirror_bhs(sb, bhs, nr_bhs);
+error:
+	fatent_brelse(&fatent);
+	for (i = 0; i < nr_bhs; i++)
+		brelse(bhs[i]);
+	unlock_fat(sbi);
+	if (dirty_fsinfo)
+		mark_fsinfo_dirty(sb);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(fat_free_clusters);
+
+struct fatent_ra {
+	sector_t cur;
+	sector_t limit;
+
+	unsigned int ra_blocks;
+	sector_t ra_advance;
+	sector_t ra_next;
+	sector_t ra_limit;
+};
+
+static void fat_ra_init(struct super_block *sb, struct fatent_ra *ra,
+			struct fat_entry *fatent, int ent_limit)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	sector_t blocknr, block_end;
+	int offset;
+	/*
+	 * This is the sequential read, so ra_pages * 2 (but try to
+	 * align the optimal hardware IO size).
+	 * [BTW, 128kb covers the whole sectors for FAT12 and FAT16]
+	 */
+	unsigned long ra_pages = sb->s_bdi->ra_pages;
+	unsigned int reada_blocks;
+
+	if (fatent->entry >= ent_limit)
+		return;
+
+	if (ra_pages > sb->s_bdi->io_pages)
+		ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages);
+	reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1);
+
+	/* Initialize the range for sequential read */
+	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+	ops->ent_blocknr(sb, ent_limit - 1, &offset, &block_end);
+	ra->cur = 0;
+	ra->limit = (block_end + 1) - blocknr;
+
+	/* Advancing the window at half size */
+	ra->ra_blocks = reada_blocks >> 1;
+	ra->ra_advance = ra->cur;
+	ra->ra_next = ra->cur;
+	ra->ra_limit = ra->cur + min_t(sector_t, reada_blocks, ra->limit);
+}
+
+/* Assuming to be called before reading a new block (increments ->cur). */
+static void fat_ent_reada(struct super_block *sb, struct fatent_ra *ra,
+			  struct fat_entry *fatent)
+{
+	if (ra->ra_next >= ra->ra_limit)
+		return;
+
+	if (ra->cur >= ra->ra_advance) {
+		struct msdos_sb_info *sbi = MSDOS_SB(sb);
+		const struct fatent_operations *ops = sbi->fatent_ops;
+		struct blk_plug plug;
+		sector_t blocknr, diff;
+		int offset;
+
+		ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+
+		diff = blocknr - ra->cur;
+		blk_start_plug(&plug);
+		/*
+		 * FIXME: we would want to directly use the bio with
+		 * pages to reduce the number of segments.
+		 */
+		for (; ra->ra_next < ra->ra_limit; ra->ra_next++)
+			sb_breadahead(sb, ra->ra_next + diff);
+		blk_finish_plug(&plug);
+
+		/* Advance the readahead window */
+		ra->ra_advance += ra->ra_blocks;
+		ra->ra_limit += min_t(sector_t,
+				      ra->ra_blocks, ra->limit - ra->ra_limit);
+	}
+	ra->cur++;
+}
+
+int fat_count_free_clusters(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct fatent_ra fatent_ra;
+	int err = 0, free;
+
+	lock_fat(sbi);
+	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
+		goto out;
+
+	free = 0;
+	fatent_init(&fatent);
+	fatent_set_entry(&fatent, FAT_START_ENT);
+	fat_ra_init(sb, &fatent_ra, &fatent, sbi->max_cluster);
+	while (fatent.entry < sbi->max_cluster) {
+		/* readahead of fat blocks */
+		fat_ent_reada(sb, &fatent_ra, &fatent);
+
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto out;
+
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE)
+				free++;
+		} while (fat_ent_next(sbi, &fatent));
+		cond_resched();
+	}
+	sbi->free_clusters = free;
+	sbi->free_clus_valid = 1;
+	mark_fsinfo_dirty(sb);
+	fatent_brelse(&fatent);
+out:
+	unlock_fat(sbi);
+	return err;
+}
+
+static int fat_trim_clusters(struct super_block *sb, u32 clus, u32 nr_clus)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	return sb_issue_discard(sb, fat_clus_to_blknr(sbi, clus),
+				nr_clus * sbi->sec_per_clus, GFP_NOFS, 0);
+}
+
+int fat_trim_fs(struct inode *inode, struct fstrim_range *range)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct fatent_ra fatent_ra;
+	u64 ent_start, ent_end, minlen, trimmed = 0;
+	u32 free = 0;
+	int err = 0;
+
+	/*
+	 * FAT data is organized as clusters, trim at the granulary of cluster.
+	 *
+	 * fstrim_range is in byte, convert values to cluster index.
+	 * Treat sectors before data region as all used, not to trim them.
+	 */
+	ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
+	ent_end = ent_start + (range->len >> sbi->cluster_bits) - 1;
+	minlen = range->minlen >> sbi->cluster_bits;
+
+	if (ent_start >= sbi->max_cluster || range->len < sbi->cluster_size)
+		return -EINVAL;
+	if (ent_end >= sbi->max_cluster)
+		ent_end = sbi->max_cluster - 1;
+
+	fatent_init(&fatent);
+	lock_fat(sbi);
+	fatent_set_entry(&fatent, ent_start);
+	fat_ra_init(sb, &fatent_ra, &fatent, ent_end + 1);
+	while (fatent.entry <= ent_end) {
+		/* readahead of fat blocks */
+		fat_ent_reada(sb, &fatent_ra, &fatent);
+
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto error;
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
+				free++;
+			} else if (free) {
+				if (free >= minlen) {
+					u32 clus = fatent.entry - free;
+
+					err = fat_trim_clusters(sb, clus, free);
+					if (err && err != -EOPNOTSUPP)
+						goto error;
+					if (!err)
+						trimmed += free;
+					err = 0;
+				}
+				free = 0;
+			}
+		} while (fat_ent_next(sbi, &fatent) && fatent.entry <= ent_end);
+
+		if (fatal_signal_pending(current)) {
+			err = -ERESTARTSYS;
+			goto error;
+		}
+
+		if (need_resched()) {
+			fatent_brelse(&fatent);
+			unlock_fat(sbi);
+			cond_resched();
+			lock_fat(sbi);
+		}
+	}
+	/* handle scenario when tail entries are all free */
+	if (free && free >= minlen) {
+		u32 clus = fatent.entry - free;
+
+		err = fat_trim_clusters(sb, clus, free);
+		if (err && err != -EOPNOTSUPP)
+			goto error;
+		if (!err)
+			trimmed += free;
+		err = 0;
+	}
+
+error:
+	fatent_brelse(&fatent);
+	unlock_fat(sbi);
+
+	range->len = trimmed << sbi->cluster_bits;
+
+	return err;
+}
diff --git a/fs/fat/file.c b/fs/fat/file.c
new file mode 100644
index 000000000..8a6b493b5
--- /dev/null
+++ b/fs/fat/file.c
@@ -0,0 +1,578 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/file.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  regular file handling primitives for fat-based filesystems
+ */
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/compat.h>
+#include <linux/mount.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/fsnotify.h>
+#include <linux/security.h>
+#include <linux/falloc.h>
+#include "fat.h"
+
+static long fat_fallocate(struct file *file, int mode,
+			  loff_t offset, loff_t len);
+
+static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
+{
+	u32 attr;
+
+	inode_lock_shared(inode);
+	attr = fat_make_attrs(inode);
+	inode_unlock_shared(inode);
+
+	return put_user(attr, user_attr);
+}
+
+static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
+{
+	struct inode *inode = file_inode(file);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	int is_dir = S_ISDIR(inode->i_mode);
+	u32 attr, oldattr;
+	struct iattr ia;
+	int err;
+
+	err = get_user(attr, user_attr);
+	if (err)
+		goto out;
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+	inode_lock(inode);
+
+	/*
+	 * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
+	 * prevents the user from turning us into a VFAT
+	 * longname entry.  Also, we obviously can't set
+	 * any of the NTFS attributes in the high 24 bits.
+	 */
+	attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
+	/* Merge in ATTR_VOLUME and ATTR_DIR */
+	attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
+		(is_dir ? ATTR_DIR : 0);
+	oldattr = fat_make_attrs(inode);
+
+	/* Equivalent to a chmod() */
+	ia.ia_valid = ATTR_MODE | ATTR_CTIME;
+	ia.ia_ctime = current_time(inode);
+	if (is_dir)
+		ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
+	else {
+		ia.ia_mode = fat_make_mode(sbi, attr,
+			S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
+	}
+
+	/* The root directory has no attributes */
+	if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
+		err = -EINVAL;
+		goto out_unlock_inode;
+	}
+
+	if (sbi->options.sys_immutable &&
+	    ((attr | oldattr) & ATTR_SYS) &&
+	    !capable(CAP_LINUX_IMMUTABLE)) {
+		err = -EPERM;
+		goto out_unlock_inode;
+	}
+
+	/*
+	 * The security check is questionable...  We single
+	 * out the RO attribute for checking by the security
+	 * module, just because it maps to a file mode.
+	 */
+	err = security_inode_setattr(file_mnt_user_ns(file),
+				     file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	/* This MUST be done before doing anything irreversible... */
+	err = fat_setattr(file_mnt_user_ns(file), file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	fsnotify_change(file->f_path.dentry, ia.ia_valid);
+	if (sbi->options.sys_immutable) {
+		if (attr & ATTR_SYS)
+			inode->i_flags |= S_IMMUTABLE;
+		else
+			inode->i_flags &= ~S_IMMUTABLE;
+	}
+
+	fat_save_attrs(inode, attr);
+	mark_inode_dirty(inode);
+out_unlock_inode:
+	inode_unlock(inode);
+	mnt_drop_write_file(file);
+out:
+	return err;
+}
+
+static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	return put_user(sbi->vol_id, user_attr);
+}
+
+static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
+{
+	struct super_block *sb = inode->i_sb;
+	struct fstrim_range __user *user_range;
+	struct fstrim_range range;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (!bdev_max_discard_sectors(sb->s_bdev))
+		return -EOPNOTSUPP;
+
+	user_range = (struct fstrim_range __user *)arg;
+	if (copy_from_user(&range, user_range, sizeof(range)))
+		return -EFAULT;
+
+	range.minlen = max_t(unsigned int, range.minlen,
+			     bdev_discard_granularity(sb->s_bdev));
+
+	err = fat_trim_fs(inode, &range);
+	if (err < 0)
+		return err;
+
+	if (copy_to_user(user_range, &range, sizeof(range)))
+		return -EFAULT;
+
+	return 0;
+}
+
+long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	u32 __user *user_attr = (u32 __user *)arg;
+
+	switch (cmd) {
+	case FAT_IOCTL_GET_ATTRIBUTES:
+		return fat_ioctl_get_attributes(inode, user_attr);
+	case FAT_IOCTL_SET_ATTRIBUTES:
+		return fat_ioctl_set_attributes(filp, user_attr);
+	case FAT_IOCTL_GET_VOLUME_ID:
+		return fat_ioctl_get_volume_id(inode, user_attr);
+	case FITRIM:
+		return fat_ioctl_fitrim(inode, arg);
+	default:
+		return -ENOTTY;	/* Inappropriate ioctl for device */
+	}
+}
+
+static int fat_file_release(struct inode *inode, struct file *filp)
+{
+	if ((filp->f_mode & FMODE_WRITE) &&
+	    MSDOS_SB(inode->i_sb)->options.flush) {
+		fat_flush_inodes(inode->i_sb, inode, NULL);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		io_schedule_timeout(HZ/10);
+	}
+	return 0;
+}
+
+int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = filp->f_mapping->host;
+	int err;
+
+	err = __generic_file_fsync(filp, start, end, datasync);
+	if (err)
+		return err;
+
+	err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
+	if (err)
+		return err;
+
+	return blkdev_issue_flush(inode->i_sb->s_bdev);
+}
+
+
+const struct file_operations fat_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.mmap		= generic_file_mmap,
+	.release	= fat_file_release,
+	.unlocked_ioctl	= fat_generic_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.fsync		= fat_file_fsync,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.fallocate	= fat_fallocate,
+};
+
+static int fat_cont_expand(struct inode *inode, loff_t size)
+{
+	struct address_space *mapping = inode->i_mapping;
+	loff_t start = inode->i_size, count = size - inode->i_size;
+	int err;
+
+	err = generic_cont_expand_simple(inode, size);
+	if (err)
+		goto out;
+
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
+	mark_inode_dirty(inode);
+	if (IS_SYNC(inode)) {
+		int err2;
+
+		/*
+		 * Opencode syncing since we don't have a file open to use
+		 * standard fsync path.
+		 */
+		err = filemap_fdatawrite_range(mapping, start,
+					       start + count - 1);
+		err2 = sync_mapping_buffers(mapping);
+		if (!err)
+			err = err2;
+		err2 = write_inode_now(inode, 1);
+		if (!err)
+			err = err2;
+		if (!err) {
+			err =  filemap_fdatawait_range(mapping, start,
+						       start + count - 1);
+		}
+	}
+out:
+	return err;
+}
+
+/*
+ * Preallocate space for a file. This implements fat's fallocate file
+ * operation, which gets called from sys_fallocate system call. User
+ * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
+ * we just allocate clusters without zeroing them out. Otherwise we
+ * allocate and zero out clusters via an expanding truncate.
+ */
+static long fat_fallocate(struct file *file, int mode,
+			  loff_t offset, loff_t len)
+{
+	int nr_cluster; /* Number of clusters to be allocated */
+	loff_t mm_bytes; /* Number of bytes to be allocated for file */
+	loff_t ondisksize; /* block aligned on-disk size in bytes*/
+	struct inode *inode = file->f_mapping->host;
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int err = 0;
+
+	/* No support for hole punch or other fallocate flags. */
+	if (mode & ~FALLOC_FL_KEEP_SIZE)
+		return -EOPNOTSUPP;
+
+	/* No support for dir */
+	if (!S_ISREG(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	inode_lock(inode);
+	if (mode & FALLOC_FL_KEEP_SIZE) {
+		ondisksize = inode->i_blocks << 9;
+		if ((offset + len) <= ondisksize)
+			goto error;
+
+		/* First compute the number of clusters to be allocated */
+		mm_bytes = offset + len - ondisksize;
+		nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
+			sbi->cluster_bits;
+
+		/* Start the allocation.We are not zeroing out the clusters */
+		while (nr_cluster-- > 0) {
+			err = fat_add_cluster(inode);
+			if (err)
+				goto error;
+		}
+	} else {
+		if ((offset + len) <= i_size_read(inode))
+			goto error;
+
+		/* This is just an expanding truncate */
+		err = fat_cont_expand(inode, (offset + len));
+	}
+
+error:
+	inode_unlock(inode);
+	return err;
+}
+
+/* Free all clusters after the skip'th cluster. */
+static int fat_free(struct inode *inode, int skip)
+{
+	struct super_block *sb = inode->i_sb;
+	int err, wait, free_start, i_start, i_logstart;
+
+	if (MSDOS_I(inode)->i_start == 0)
+		return 0;
+
+	fat_cache_inval_inode(inode);
+
+	wait = IS_DIRSYNC(inode);
+	i_start = free_start = MSDOS_I(inode)->i_start;
+	i_logstart = MSDOS_I(inode)->i_logstart;
+
+	/* First, we write the new file size. */
+	if (!skip) {
+		MSDOS_I(inode)->i_start = 0;
+		MSDOS_I(inode)->i_logstart = 0;
+	}
+	MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
+	if (wait) {
+		err = fat_sync_inode(inode);
+		if (err) {
+			MSDOS_I(inode)->i_start = i_start;
+			MSDOS_I(inode)->i_logstart = i_logstart;
+			return err;
+		}
+	} else
+		mark_inode_dirty(inode);
+
+	/* Write a new EOF, and get the remaining cluster chain for freeing. */
+	if (skip) {
+		struct fat_entry fatent;
+		int ret, fclus, dclus;
+
+		ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
+		if (ret < 0)
+			return ret;
+		else if (ret == FAT_ENT_EOF)
+			return 0;
+
+		fatent_init(&fatent);
+		ret = fat_ent_read(inode, &fatent, dclus);
+		if (ret == FAT_ENT_EOF) {
+			fatent_brelse(&fatent);
+			return 0;
+		} else if (ret == FAT_ENT_FREE) {
+			fat_fs_error(sb,
+				     "%s: invalid cluster chain (i_pos %lld)",
+				     __func__, MSDOS_I(inode)->i_pos);
+			ret = -EIO;
+		} else if (ret > 0) {
+			err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
+			if (err)
+				ret = err;
+		}
+		fatent_brelse(&fatent);
+		if (ret < 0)
+			return ret;
+
+		free_start = ret;
+	}
+	inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
+
+	/* Freeing the remained cluster chain */
+	return fat_free_clusters(inode, free_start);
+}
+
+void fat_truncate_blocks(struct inode *inode, loff_t offset)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	const unsigned int cluster_size = sbi->cluster_size;
+	int nr_clusters;
+
+	/*
+	 * This protects against truncating a file bigger than it was then
+	 * trying to write into the hole.
+	 */
+	if (MSDOS_I(inode)->mmu_private > offset)
+		MSDOS_I(inode)->mmu_private = offset;
+
+	nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
+
+	fat_free(inode, nr_clusters);
+	fat_flush_inodes(inode->i_sb, inode, NULL);
+}
+
+int fat_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
+	generic_fillattr(mnt_userns, inode, stat);
+	stat->blksize = sbi->cluster_size;
+
+	if (sbi->options.nfs == FAT_NFS_NOSTALE_RO) {
+		/* Use i_pos for ino. This is used as fileid of nfs. */
+		stat->ino = fat_i_pos_read(sbi, inode);
+	}
+
+	if (sbi->options.isvfat && request_mask & STATX_BTIME) {
+		stat->result_mask |= STATX_BTIME;
+		stat->btime = MSDOS_I(inode)->i_crtime;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_getattr);
+
+static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
+			     struct inode *inode, umode_t *mode_ptr)
+{
+	umode_t mask, perm;
+
+	/*
+	 * Note, the basic check is already done by a caller of
+	 * (attr->ia_mode & ~FAT_VALID_MODE)
+	 */
+
+	if (S_ISREG(inode->i_mode))
+		mask = sbi->options.fs_fmask;
+	else
+		mask = sbi->options.fs_dmask;
+
+	perm = *mode_ptr & ~(S_IFMT | mask);
+
+	/*
+	 * Of the r and x bits, all (subject to umask) must be present. Of the
+	 * w bits, either all (subject to umask) or none must be present.
+	 *
+	 * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
+	 */
+	if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
+		return -EPERM;
+	if (fat_mode_can_hold_ro(inode)) {
+		if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
+			return -EPERM;
+	} else {
+		if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
+			return -EPERM;
+	}
+
+	*mode_ptr &= S_IFMT | perm;
+
+	return 0;
+}
+
+static int fat_allow_set_time(struct user_namespace *mnt_userns,
+			      struct msdos_sb_info *sbi, struct inode *inode)
+{
+	umode_t allow_utime = sbi->options.allow_utime;
+
+	if (!vfsuid_eq_kuid(i_uid_into_vfsuid(mnt_userns, inode),
+			    current_fsuid())) {
+		if (vfsgid_in_group_p(i_gid_into_vfsgid(mnt_userns, inode)))
+			allow_utime >>= 3;
+		if (allow_utime & MAY_WRITE)
+			return 1;
+	}
+
+	/* use a default check */
+	return 0;
+}
+
+#define TIMES_SET_FLAGS	(ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
+/* valid file mode bits */
+#define FAT_VALID_MODE	(S_IFREG | S_IFDIR | S_IRWXUGO)
+
+int fat_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
+	struct inode *inode = d_inode(dentry);
+	unsigned int ia_valid;
+	int error;
+
+	/* Check for setting the inode time. */
+	ia_valid = attr->ia_valid;
+	if (ia_valid & TIMES_SET_FLAGS) {
+		if (fat_allow_set_time(mnt_userns, sbi, inode))
+			attr->ia_valid &= ~TIMES_SET_FLAGS;
+	}
+
+	error = setattr_prepare(mnt_userns, dentry, attr);
+	attr->ia_valid = ia_valid;
+	if (error) {
+		if (sbi->options.quiet)
+			error = 0;
+		goto out;
+	}
+
+	/*
+	 * Expand the file. Since inode_setattr() updates ->i_size
+	 * before calling the ->truncate(), but FAT needs to fill the
+	 * hole before it. XXX: this is no longer true with new truncate
+	 * sequence.
+	 */
+	if (attr->ia_valid & ATTR_SIZE) {
+		inode_dio_wait(inode);
+
+		if (attr->ia_size > inode->i_size) {
+			error = fat_cont_expand(inode, attr->ia_size);
+			if (error || attr->ia_valid == ATTR_SIZE)
+				goto out;
+			attr->ia_valid &= ~ATTR_SIZE;
+		}
+	}
+
+	if (((attr->ia_valid & ATTR_UID) &&
+	     (!uid_eq(from_vfsuid(mnt_userns, i_user_ns(inode), attr->ia_vfsuid),
+		      sbi->options.fs_uid))) ||
+	    ((attr->ia_valid & ATTR_GID) &&
+	     (!gid_eq(from_vfsgid(mnt_userns, i_user_ns(inode), attr->ia_vfsgid),
+		      sbi->options.fs_gid))) ||
+	    ((attr->ia_valid & ATTR_MODE) &&
+	     (attr->ia_mode & ~FAT_VALID_MODE)))
+		error = -EPERM;
+
+	if (error) {
+		if (sbi->options.quiet)
+			error = 0;
+		goto out;
+	}
+
+	/*
+	 * We don't return -EPERM here. Yes, strange, but this is too
+	 * old behavior.
+	 */
+	if (attr->ia_valid & ATTR_MODE) {
+		if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
+			attr->ia_valid &= ~ATTR_MODE;
+	}
+
+	if (attr->ia_valid & ATTR_SIZE) {
+		error = fat_block_truncate_page(inode, attr->ia_size);
+		if (error)
+			goto out;
+		down_write(&MSDOS_I(inode)->truncate_lock);
+		truncate_setsize(inode, attr->ia_size);
+		fat_truncate_blocks(inode, attr->ia_size);
+		up_write(&MSDOS_I(inode)->truncate_lock);
+	}
+
+	/*
+	 * setattr_copy can't truncate these appropriately, so we'll
+	 * copy them ourselves
+	 */
+	if (attr->ia_valid & ATTR_ATIME)
+		fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
+	if (attr->ia_valid & ATTR_CTIME)
+		fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
+	if (attr->ia_valid & ATTR_MTIME)
+		fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
+	attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
+
+	setattr_copy(mnt_userns, inode, attr);
+	mark_inode_dirty(inode);
+out:
+	return error;
+}
+EXPORT_SYMBOL_GPL(fat_setattr);
+
+const struct inode_operations fat_file_inode_operations = {
+	.setattr	= fat_setattr,
+	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
+};
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
new file mode 100644
index 000000000..1cbcc4608
--- /dev/null
+++ b/fs/fat/inode.c
@@ -0,0 +1,1975 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/inode.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *  VFAT extensions by Gordon Chaffee, merged with msdos fs by Henrik Storner
+ *  Rewritten for the constant inumbers support by Al Viro
+ *
+ *  Fixes:
+ *
+ *	Max Cohan: Fixed invalid FSINFO offset when info_sector is 0
+ */
+
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/mpage.h>
+#include <linux/vfs.h>
+#include <linux/seq_file.h>
+#include <linux/parser.h>
+#include <linux/uio.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <asm/unaligned.h>
+#include <linux/random.h>
+#include <linux/iversion.h>
+#include "fat.h"
+
+#ifndef CONFIG_FAT_DEFAULT_IOCHARSET
+/* if user don't select VFAT, this is undefined. */
+#define CONFIG_FAT_DEFAULT_IOCHARSET	""
+#endif
+
+#define KB_IN_SECTORS 2
+
+/* DOS dates from 1980/1/1 through 2107/12/31 */
+#define FAT_DATE_MIN (0<<9 | 1<<5 | 1)
+#define FAT_DATE_MAX (127<<9 | 12<<5 | 31)
+#define FAT_TIME_MAX (23<<11 | 59<<5 | 29)
+
+/*
+ * A deserialized copy of the on-disk structure laid out in struct
+ * fat_boot_sector.
+ */
+struct fat_bios_param_block {
+	u16	fat_sector_size;
+	u8	fat_sec_per_clus;
+	u16	fat_reserved;
+	u8	fat_fats;
+	u16	fat_dir_entries;
+	u16	fat_sectors;
+	u16	fat_fat_length;
+	u32	fat_total_sect;
+
+	u8	fat16_state;
+	u32	fat16_vol_id;
+
+	u32	fat32_length;
+	u32	fat32_root_cluster;
+	u16	fat32_info_sector;
+	u8	fat32_state;
+	u32	fat32_vol_id;
+};
+
+static int fat_default_codepage = CONFIG_FAT_DEFAULT_CODEPAGE;
+static char fat_default_iocharset[] = CONFIG_FAT_DEFAULT_IOCHARSET;
+
+static struct fat_floppy_defaults {
+	unsigned nr_sectors;
+	unsigned sec_per_clus;
+	unsigned dir_entries;
+	unsigned media;
+	unsigned fat_length;
+} floppy_defaults[] = {
+{
+	.nr_sectors = 160 * KB_IN_SECTORS,
+	.sec_per_clus = 1,
+	.dir_entries = 64,
+	.media = 0xFE,
+	.fat_length = 1,
+},
+{
+	.nr_sectors = 180 * KB_IN_SECTORS,
+	.sec_per_clus = 1,
+	.dir_entries = 64,
+	.media = 0xFC,
+	.fat_length = 2,
+},
+{
+	.nr_sectors = 320 * KB_IN_SECTORS,
+	.sec_per_clus = 2,
+	.dir_entries = 112,
+	.media = 0xFF,
+	.fat_length = 1,
+},
+{
+	.nr_sectors = 360 * KB_IN_SECTORS,
+	.sec_per_clus = 2,
+	.dir_entries = 112,
+	.media = 0xFD,
+	.fat_length = 2,
+},
+};
+
+int fat_add_cluster(struct inode *inode)
+{
+	int err, cluster;
+
+	err = fat_alloc_clusters(inode, &cluster, 1);
+	if (err)
+		return err;
+	/* FIXME: this cluster should be added after data of this
+	 * cluster is writed */
+	err = fat_chain_add(inode, cluster, 1);
+	if (err)
+		fat_free_clusters(inode, cluster);
+	return err;
+}
+
+static inline int __fat_get_block(struct inode *inode, sector_t iblock,
+				  unsigned long *max_blocks,
+				  struct buffer_head *bh_result, int create)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	unsigned long mapped_blocks;
+	sector_t phys, last_block;
+	int err, offset;
+
+	err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create, false);
+	if (err)
+		return err;
+	if (phys) {
+		map_bh(bh_result, sb, phys);
+		*max_blocks = min(mapped_blocks, *max_blocks);
+		return 0;
+	}
+	if (!create)
+		return 0;
+
+	if (iblock != MSDOS_I(inode)->mmu_private >> sb->s_blocksize_bits) {
+		fat_fs_error(sb, "corrupted file size (i_pos %lld, %lld)",
+			MSDOS_I(inode)->i_pos, MSDOS_I(inode)->mmu_private);
+		return -EIO;
+	}
+
+	last_block = inode->i_blocks >> (sb->s_blocksize_bits - 9);
+	offset = (unsigned long)iblock & (sbi->sec_per_clus - 1);
+	/*
+	 * allocate a cluster according to the following.
+	 * 1) no more available blocks
+	 * 2) not part of fallocate region
+	 */
+	if (!offset && !(iblock < last_block)) {
+		/* TODO: multiple cluster allocation would be desirable. */
+		err = fat_add_cluster(inode);
+		if (err)
+			return err;
+	}
+	/* available blocks on this cluster */
+	mapped_blocks = sbi->sec_per_clus - offset;
+
+	*max_blocks = min(mapped_blocks, *max_blocks);
+	MSDOS_I(inode)->mmu_private += *max_blocks << sb->s_blocksize_bits;
+
+	err = fat_bmap(inode, iblock, &phys, &mapped_blocks, create, false);
+	if (err)
+		return err;
+	if (!phys) {
+		fat_fs_error(sb,
+			     "invalid FAT chain (i_pos %lld, last_block %llu)",
+			     MSDOS_I(inode)->i_pos,
+			     (unsigned long long)last_block);
+		return -EIO;
+	}
+
+	BUG_ON(*max_blocks != mapped_blocks);
+	set_buffer_new(bh_result);
+	map_bh(bh_result, sb, phys);
+
+	return 0;
+}
+
+static int fat_get_block(struct inode *inode, sector_t iblock,
+			 struct buffer_head *bh_result, int create)
+{
+	struct super_block *sb = inode->i_sb;
+	unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
+	int err;
+
+	err = __fat_get_block(inode, iblock, &max_blocks, bh_result, create);
+	if (err)
+		return err;
+	bh_result->b_size = max_blocks << sb->s_blocksize_bits;
+	return 0;
+}
+
+static int fat_writepage(struct page *page, struct writeback_control *wbc)
+{
+	return block_write_full_page(page, fat_get_block, wbc);
+}
+
+static int fat_writepages(struct address_space *mapping,
+			  struct writeback_control *wbc)
+{
+	return mpage_writepages(mapping, wbc, fat_get_block);
+}
+
+static int fat_read_folio(struct file *file, struct folio *folio)
+{
+	return mpage_read_folio(folio, fat_get_block);
+}
+
+static void fat_readahead(struct readahead_control *rac)
+{
+	mpage_readahead(rac, fat_get_block);
+}
+
+static void fat_write_failed(struct address_space *mapping, loff_t to)
+{
+	struct inode *inode = mapping->host;
+
+	if (to > inode->i_size) {
+		truncate_pagecache(inode, inode->i_size);
+		fat_truncate_blocks(inode, inode->i_size);
+	}
+}
+
+static int fat_write_begin(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len,
+			struct page **pagep, void **fsdata)
+{
+	int err;
+
+	*pagep = NULL;
+	err = cont_write_begin(file, mapping, pos, len,
+				pagep, fsdata, fat_get_block,
+				&MSDOS_I(mapping->host)->mmu_private);
+	if (err < 0)
+		fat_write_failed(mapping, pos + len);
+	return err;
+}
+
+static int fat_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *pagep, void *fsdata)
+{
+	struct inode *inode = mapping->host;
+	int err;
+	err = generic_write_end(file, mapping, pos, len, copied, pagep, fsdata);
+	if (err < len)
+		fat_write_failed(mapping, pos + len);
+	if (!(err < 0) && !(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
+		fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
+		MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
+		mark_inode_dirty(inode);
+	}
+	return err;
+}
+
+static ssize_t fat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	size_t count = iov_iter_count(iter);
+	loff_t offset = iocb->ki_pos;
+	ssize_t ret;
+
+	if (iov_iter_rw(iter) == WRITE) {
+		/*
+		 * FIXME: blockdev_direct_IO() doesn't use ->write_begin(),
+		 * so we need to update the ->mmu_private to block boundary.
+		 *
+		 * But we must fill the remaining area or hole by nul for
+		 * updating ->mmu_private.
+		 *
+		 * Return 0, and fallback to normal buffered write.
+		 */
+		loff_t size = offset + count;
+		if (MSDOS_I(inode)->mmu_private < size)
+			return 0;
+	}
+
+	/*
+	 * FAT need to use the DIO_LOCKING for avoiding the race
+	 * condition of fat_get_block() and ->truncate().
+	 */
+	ret = blockdev_direct_IO(iocb, inode, iter, fat_get_block);
+	if (ret < 0 && iov_iter_rw(iter) == WRITE)
+		fat_write_failed(mapping, offset + count);
+
+	return ret;
+}
+
+static int fat_get_block_bmap(struct inode *inode, sector_t iblock,
+		struct buffer_head *bh_result, int create)
+{
+	struct super_block *sb = inode->i_sb;
+	unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
+	int err;
+	sector_t bmap;
+	unsigned long mapped_blocks;
+
+	BUG_ON(create != 0);
+
+	err = fat_bmap(inode, iblock, &bmap, &mapped_blocks, create, true);
+	if (err)
+		return err;
+
+	if (bmap) {
+		map_bh(bh_result, sb, bmap);
+		max_blocks = min(mapped_blocks, max_blocks);
+	}
+
+	bh_result->b_size = max_blocks << sb->s_blocksize_bits;
+
+	return 0;
+}
+
+static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
+{
+	sector_t blocknr;
+
+	/* fat_get_cluster() assumes the requested blocknr isn't truncated. */
+	down_read(&MSDOS_I(mapping->host)->truncate_lock);
+	blocknr = generic_block_bmap(mapping, block, fat_get_block_bmap);
+	up_read(&MSDOS_I(mapping->host)->truncate_lock);
+
+	return blocknr;
+}
+
+/*
+ * fat_block_truncate_page() zeroes out a mapping from file offset `from'
+ * up to the end of the block which corresponds to `from'.
+ * This is required during truncate to physically zeroout the tail end
+ * of that block so it doesn't yield old data if the file is later grown.
+ * Also, avoid causing failure from fsx for cases of "data past EOF"
+ */
+int fat_block_truncate_page(struct inode *inode, loff_t from)
+{
+	return block_truncate_page(inode->i_mapping, from, fat_get_block);
+}
+
+static const struct address_space_operations fat_aops = {
+	.dirty_folio	= block_dirty_folio,
+	.invalidate_folio = block_invalidate_folio,
+	.read_folio	= fat_read_folio,
+	.readahead	= fat_readahead,
+	.writepage	= fat_writepage,
+	.writepages	= fat_writepages,
+	.write_begin	= fat_write_begin,
+	.write_end	= fat_write_end,
+	.direct_IO	= fat_direct_IO,
+	.bmap		= _fat_bmap
+};
+
+/*
+ * New FAT inode stuff. We do the following:
+ *	a) i_ino is constant and has nothing with on-disk location.
+ *	b) FAT manages its own cache of directory entries.
+ *	c) *This* cache is indexed by on-disk location.
+ *	d) inode has an associated directory entry, all right, but
+ *		it may be unhashed.
+ *	e) currently entries are stored within struct inode. That should
+ *		change.
+ *	f) we deal with races in the following way:
+ *		1. readdir() and lookup() do FAT-dir-cache lookup.
+ *		2. rename() unhashes the F-d-c entry and rehashes it in
+ *			a new place.
+ *		3. unlink() and rmdir() unhash F-d-c entry.
+ *		4. fat_write_inode() checks whether the thing is unhashed.
+ *			If it is we silently return. If it isn't we do bread(),
+ *			check if the location is still valid and retry if it
+ *			isn't. Otherwise we do changes.
+ *		5. Spinlock is used to protect hash/unhash/location check/lookup
+ *		6. fat_evict_inode() unhashes the F-d-c entry.
+ *		7. lookup() and readdir() do igrab() if they find a F-d-c entry
+ *			and consider negative result as cache miss.
+ */
+
+static void fat_hash_init(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int i;
+
+	spin_lock_init(&sbi->inode_hash_lock);
+	for (i = 0; i < FAT_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
+}
+
+static inline unsigned long fat_hash(loff_t i_pos)
+{
+	return hash_32(i_pos, FAT_HASH_BITS);
+}
+
+static void dir_hash_init(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int i;
+
+	spin_lock_init(&sbi->dir_hash_lock);
+	for (i = 0; i < FAT_HASH_SIZE; i++)
+		INIT_HLIST_HEAD(&sbi->dir_hashtable[i]);
+}
+
+void fat_attach(struct inode *inode, loff_t i_pos)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
+	if (inode->i_ino != MSDOS_ROOT_INO) {
+		struct hlist_head *head =   sbi->inode_hashtable
+					  + fat_hash(i_pos);
+
+		spin_lock(&sbi->inode_hash_lock);
+		MSDOS_I(inode)->i_pos = i_pos;
+		hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
+		spin_unlock(&sbi->inode_hash_lock);
+	}
+
+	/* If NFS support is enabled, cache the mapping of start cluster
+	 * to directory inode. This is used during reconnection of
+	 * dentries to the filesystem root.
+	 */
+	if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
+		struct hlist_head *d_head = sbi->dir_hashtable;
+		d_head += fat_dir_hash(MSDOS_I(inode)->i_logstart);
+
+		spin_lock(&sbi->dir_hash_lock);
+		hlist_add_head(&MSDOS_I(inode)->i_dir_hash, d_head);
+		spin_unlock(&sbi->dir_hash_lock);
+	}
+}
+EXPORT_SYMBOL_GPL(fat_attach);
+
+void fat_detach(struct inode *inode)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	spin_lock(&sbi->inode_hash_lock);
+	MSDOS_I(inode)->i_pos = 0;
+	hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
+	spin_unlock(&sbi->inode_hash_lock);
+
+	if (S_ISDIR(inode->i_mode) && sbi->options.nfs) {
+		spin_lock(&sbi->dir_hash_lock);
+		hlist_del_init(&MSDOS_I(inode)->i_dir_hash);
+		spin_unlock(&sbi->dir_hash_lock);
+	}
+}
+EXPORT_SYMBOL_GPL(fat_detach);
+
+struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
+	struct msdos_inode_info *i;
+	struct inode *inode = NULL;
+
+	spin_lock(&sbi->inode_hash_lock);
+	hlist_for_each_entry(i, head, i_fat_hash) {
+		BUG_ON(i->vfs_inode.i_sb != sb);
+		if (i->i_pos != i_pos)
+			continue;
+		inode = igrab(&i->vfs_inode);
+		if (inode)
+			break;
+	}
+	spin_unlock(&sbi->inode_hash_lock);
+	return inode;
+}
+
+static int is_exec(unsigned char *extension)
+{
+	unsigned char exe_extensions[] = "EXECOMBAT", *walk;
+
+	for (walk = exe_extensions; *walk; walk += 3)
+		if (!strncmp(extension, walk, 3))
+			return 1;
+	return 0;
+}
+
+static int fat_calc_dir_size(struct inode *inode)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	int ret, fclus, dclus;
+
+	inode->i_size = 0;
+	if (MSDOS_I(inode)->i_start == 0)
+		return 0;
+
+	ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
+	if (ret < 0)
+		return ret;
+	inode->i_size = (fclus + 1) << sbi->cluster_bits;
+
+	return 0;
+}
+
+static int fat_validate_dir(struct inode *dir)
+{
+	struct super_block *sb = dir->i_sb;
+
+	if (dir->i_nlink < 2) {
+		/* Directory should have "."/".." entries at least. */
+		fat_fs_error(sb, "corrupted directory (invalid entries)");
+		return -EIO;
+	}
+	if (MSDOS_I(dir)->i_start == 0 ||
+	    MSDOS_I(dir)->i_start == MSDOS_SB(sb)->root_cluster) {
+		/* Directory should point valid cluster. */
+		fat_fs_error(sb, "corrupted directory (invalid i_start)");
+		return -EIO;
+	}
+	return 0;
+}
+
+/* doesn't deal with root inode */
+int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	int error;
+
+	MSDOS_I(inode)->i_pos = 0;
+	inode->i_uid = sbi->options.fs_uid;
+	inode->i_gid = sbi->options.fs_gid;
+	inode_inc_iversion(inode);
+	inode->i_generation = get_random_u32();
+
+	if ((de->attr & ATTR_DIR) && !IS_FREE(de->name)) {
+		inode->i_generation &= ~1;
+		inode->i_mode = fat_make_mode(sbi, de->attr, S_IRWXUGO);
+		inode->i_op = sbi->dir_ops;
+		inode->i_fop = &fat_dir_operations;
+
+		MSDOS_I(inode)->i_start = fat_get_start(sbi, de);
+		MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
+		error = fat_calc_dir_size(inode);
+		if (error < 0)
+			return error;
+		MSDOS_I(inode)->mmu_private = inode->i_size;
+
+		set_nlink(inode, fat_subdirs(inode));
+
+		error = fat_validate_dir(inode);
+		if (error < 0)
+			return error;
+	} else { /* not a directory */
+		inode->i_generation |= 1;
+		inode->i_mode = fat_make_mode(sbi, de->attr,
+			((sbi->options.showexec && !is_exec(de->name + 8))
+			 ? S_IRUGO|S_IWUGO : S_IRWXUGO));
+		MSDOS_I(inode)->i_start = fat_get_start(sbi, de);
+
+		MSDOS_I(inode)->i_logstart = MSDOS_I(inode)->i_start;
+		inode->i_size = le32_to_cpu(de->size);
+		inode->i_op = &fat_file_inode_operations;
+		inode->i_fop = &fat_file_operations;
+		inode->i_mapping->a_ops = &fat_aops;
+		MSDOS_I(inode)->mmu_private = inode->i_size;
+	}
+	if (de->attr & ATTR_SYS) {
+		if (sbi->options.sys_immutable)
+			inode->i_flags |= S_IMMUTABLE;
+	}
+	fat_save_attrs(inode, de->attr);
+
+	inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
+			   & ~((loff_t)sbi->cluster_size - 1)) >> 9;
+
+	fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0);
+	inode->i_ctime = inode->i_mtime;
+	if (sbi->options.isvfat) {
+		fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
+		fat_time_fat2unix(sbi, &MSDOS_I(inode)->i_crtime, de->ctime,
+				  de->cdate, de->ctime_cs);
+	} else
+		inode->i_atime = fat_truncate_atime(sbi, &inode->i_mtime);
+
+	return 0;
+}
+
+static inline void fat_lock_build_inode(struct msdos_sb_info *sbi)
+{
+	if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+		mutex_lock(&sbi->nfs_build_inode_lock);
+}
+
+static inline void fat_unlock_build_inode(struct msdos_sb_info *sbi)
+{
+	if (sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+		mutex_unlock(&sbi->nfs_build_inode_lock);
+}
+
+struct inode *fat_build_inode(struct super_block *sb,
+			struct msdos_dir_entry *de, loff_t i_pos)
+{
+	struct inode *inode;
+	int err;
+
+	fat_lock_build_inode(MSDOS_SB(sb));
+	inode = fat_iget(sb, i_pos);
+	if (inode)
+		goto out;
+	inode = new_inode(sb);
+	if (!inode) {
+		inode = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+	inode->i_ino = iunique(sb, MSDOS_ROOT_INO);
+	inode_set_iversion(inode, 1);
+	err = fat_fill_inode(inode, de);
+	if (err) {
+		iput(inode);
+		inode = ERR_PTR(err);
+		goto out;
+	}
+	fat_attach(inode, i_pos);
+	insert_inode_hash(inode);
+out:
+	fat_unlock_build_inode(MSDOS_SB(sb));
+	return inode;
+}
+
+EXPORT_SYMBOL_GPL(fat_build_inode);
+
+static int __fat_write_inode(struct inode *inode, int wait);
+
+static void fat_free_eofblocks(struct inode *inode)
+{
+	/* Release unwritten fallocated blocks on inode eviction. */
+	if ((inode->i_blocks << 9) >
+			round_up(MSDOS_I(inode)->mmu_private,
+				MSDOS_SB(inode->i_sb)->cluster_size)) {
+		int err;
+
+		fat_truncate_blocks(inode, MSDOS_I(inode)->mmu_private);
+		/* Fallocate results in updating the i_start/iogstart
+		 * for the zero byte file. So, make it return to
+		 * original state during evict and commit it to avoid
+		 * any corruption on the next access to the cluster
+		 * chain for the file.
+		 */
+		err = __fat_write_inode(inode, inode_needs_sync(inode));
+		if (err) {
+			fat_msg(inode->i_sb, KERN_WARNING, "Failed to "
+					"update on disk inode for unused "
+					"fallocated blocks, inode could be "
+					"corrupted. Please run fsck");
+		}
+
+	}
+}
+
+static void fat_evict_inode(struct inode *inode)
+{
+	truncate_inode_pages_final(&inode->i_data);
+	if (!inode->i_nlink) {
+		inode->i_size = 0;
+		fat_truncate_blocks(inode, 0);
+	} else
+		fat_free_eofblocks(inode);
+
+	invalidate_inode_buffers(inode);
+	clear_inode(inode);
+	fat_cache_inval_inode(inode);
+	fat_detach(inode);
+}
+
+static void fat_set_state(struct super_block *sb,
+			unsigned int set, unsigned int force)
+{
+	struct buffer_head *bh;
+	struct fat_boot_sector *b;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	/* do not change any thing if mounted read only */
+	if (sb_rdonly(sb) && !force)
+		return;
+
+	/* do not change state if fs was dirty */
+	if (sbi->dirty) {
+		/* warn only on set (mount). */
+		if (set)
+			fat_msg(sb, KERN_WARNING, "Volume was not properly "
+				"unmounted. Some data may be corrupt. "
+				"Please run fsck.");
+		return;
+	}
+
+	bh = sb_bread(sb, 0);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "unable to read boot sector "
+			"to mark fs as dirty");
+		return;
+	}
+
+	b = (struct fat_boot_sector *) bh->b_data;
+
+	if (is_fat32(sbi)) {
+		if (set)
+			b->fat32.state |= FAT_STATE_DIRTY;
+		else
+			b->fat32.state &= ~FAT_STATE_DIRTY;
+	} else /* fat 16 and 12 */ {
+		if (set)
+			b->fat16.state |= FAT_STATE_DIRTY;
+		else
+			b->fat16.state &= ~FAT_STATE_DIRTY;
+	}
+
+	mark_buffer_dirty(bh);
+	sync_dirty_buffer(bh);
+	brelse(bh);
+}
+
+static void fat_reset_iocharset(struct fat_mount_options *opts)
+{
+	if (opts->iocharset != fat_default_iocharset) {
+		/* Note: opts->iocharset can be NULL here */
+		kfree(opts->iocharset);
+		opts->iocharset = fat_default_iocharset;
+	}
+}
+
+static void delayed_free(struct rcu_head *p)
+{
+	struct msdos_sb_info *sbi = container_of(p, struct msdos_sb_info, rcu);
+	unload_nls(sbi->nls_disk);
+	unload_nls(sbi->nls_io);
+	fat_reset_iocharset(&sbi->options);
+	kfree(sbi);
+}
+
+static void fat_put_super(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	fat_set_state(sb, 0, 0);
+
+	iput(sbi->fsinfo_inode);
+	iput(sbi->fat_inode);
+
+	call_rcu(&sbi->rcu, delayed_free);
+}
+
+static struct kmem_cache *fat_inode_cachep;
+
+static struct inode *fat_alloc_inode(struct super_block *sb)
+{
+	struct msdos_inode_info *ei;
+	ei = alloc_inode_sb(sb, fat_inode_cachep, GFP_NOFS);
+	if (!ei)
+		return NULL;
+
+	init_rwsem(&ei->truncate_lock);
+	/* Zeroing to allow iput() even if partial initialized inode. */
+	ei->mmu_private = 0;
+	ei->i_start = 0;
+	ei->i_logstart = 0;
+	ei->i_attrs = 0;
+	ei->i_pos = 0;
+	ei->i_crtime.tv_sec = 0;
+	ei->i_crtime.tv_nsec = 0;
+
+	return &ei->vfs_inode;
+}
+
+static void fat_free_inode(struct inode *inode)
+{
+	kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
+}
+
+static void init_once(void *foo)
+{
+	struct msdos_inode_info *ei = (struct msdos_inode_info *)foo;
+
+	spin_lock_init(&ei->cache_lru_lock);
+	ei->nr_caches = 0;
+	ei->cache_valid_id = FAT_CACHE_VALID + 1;
+	INIT_LIST_HEAD(&ei->cache_lru);
+	INIT_HLIST_NODE(&ei->i_fat_hash);
+	INIT_HLIST_NODE(&ei->i_dir_hash);
+	inode_init_once(&ei->vfs_inode);
+}
+
+static int __init fat_init_inodecache(void)
+{
+	fat_inode_cachep = kmem_cache_create("fat_inode_cache",
+					     sizeof(struct msdos_inode_info),
+					     0, (SLAB_RECLAIM_ACCOUNT|
+						SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+					     init_once);
+	if (fat_inode_cachep == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+static void __exit fat_destroy_inodecache(void)
+{
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+	kmem_cache_destroy(fat_inode_cachep);
+}
+
+static int fat_remount(struct super_block *sb, int *flags, char *data)
+{
+	bool new_rdonly;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	*flags |= SB_NODIRATIME | (sbi->options.isvfat ? 0 : SB_NOATIME);
+
+	sync_filesystem(sb);
+
+	/* make sure we update state on remount. */
+	new_rdonly = *flags & SB_RDONLY;
+	if (new_rdonly != sb_rdonly(sb)) {
+		if (new_rdonly)
+			fat_set_state(sb, 0, 0);
+		else
+			fat_set_state(sb, 1, 1);
+	}
+	return 0;
+}
+
+static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
+
+	/* If the count of free cluster is still unknown, counts it here. */
+	if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
+		int err = fat_count_free_clusters(dentry->d_sb);
+		if (err)
+			return err;
+	}
+
+	buf->f_type = dentry->d_sb->s_magic;
+	buf->f_bsize = sbi->cluster_size;
+	buf->f_blocks = sbi->max_cluster - FAT_START_ENT;
+	buf->f_bfree = sbi->free_clusters;
+	buf->f_bavail = sbi->free_clusters;
+	buf->f_fsid = u64_to_fsid(id);
+	buf->f_namelen =
+		(sbi->options.isvfat ? FAT_LFN_LEN : 12) * NLS_MAX_CHARSET_SIZE;
+
+	return 0;
+}
+
+static int __fat_write_inode(struct inode *inode, int wait)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	struct msdos_dir_entry *raw_entry;
+	loff_t i_pos;
+	sector_t blocknr;
+	int err, offset;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return 0;
+
+retry:
+	i_pos = fat_i_pos_read(sbi, inode);
+	if (!i_pos)
+		return 0;
+
+	fat_get_blknr_offset(sbi, i_pos, &blocknr, &offset);
+	bh = sb_bread(sb, blocknr);
+	if (!bh) {
+		fat_msg(sb, KERN_ERR, "unable to read inode block "
+		       "for updating (i_pos %lld)", i_pos);
+		return -EIO;
+	}
+	spin_lock(&sbi->inode_hash_lock);
+	if (i_pos != MSDOS_I(inode)->i_pos) {
+		spin_unlock(&sbi->inode_hash_lock);
+		brelse(bh);
+		goto retry;
+	}
+
+	raw_entry = &((struct msdos_dir_entry *) (bh->b_data))[offset];
+	if (S_ISDIR(inode->i_mode))
+		raw_entry->size = 0;
+	else
+		raw_entry->size = cpu_to_le32(inode->i_size);
+	raw_entry->attr = fat_make_attrs(inode);
+	fat_set_start(raw_entry, MSDOS_I(inode)->i_logstart);
+	fat_time_unix2fat(sbi, &inode->i_mtime, &raw_entry->time,
+			  &raw_entry->date, NULL);
+	if (sbi->options.isvfat) {
+		__le16 atime;
+		fat_time_unix2fat(sbi, &inode->i_atime, &atime,
+				  &raw_entry->adate, NULL);
+		fat_time_unix2fat(sbi, &MSDOS_I(inode)->i_crtime, &raw_entry->ctime,
+				  &raw_entry->cdate, &raw_entry->ctime_cs);
+	}
+	spin_unlock(&sbi->inode_hash_lock);
+	mark_buffer_dirty(bh);
+	err = 0;
+	if (wait)
+		err = sync_dirty_buffer(bh);
+	brelse(bh);
+	return err;
+}
+
+static int fat_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	int err;
+
+	if (inode->i_ino == MSDOS_FSINFO_INO) {
+		struct super_block *sb = inode->i_sb;
+
+		mutex_lock(&MSDOS_SB(sb)->s_lock);
+		err = fat_clusters_flush(sb);
+		mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	} else
+		err = __fat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
+
+	return err;
+}
+
+int fat_sync_inode(struct inode *inode)
+{
+	return __fat_write_inode(inode, 1);
+}
+
+EXPORT_SYMBOL_GPL(fat_sync_inode);
+
+static int fat_show_options(struct seq_file *m, struct dentry *root);
+static const struct super_operations fat_sops = {
+	.alloc_inode	= fat_alloc_inode,
+	.free_inode	= fat_free_inode,
+	.write_inode	= fat_write_inode,
+	.evict_inode	= fat_evict_inode,
+	.put_super	= fat_put_super,
+	.statfs		= fat_statfs,
+	.remount_fs	= fat_remount,
+
+	.show_options	= fat_show_options,
+};
+
+static int fat_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(root->d_sb);
+	struct fat_mount_options *opts = &sbi->options;
+	int isvfat = opts->isvfat;
+
+	if (!uid_eq(opts->fs_uid, GLOBAL_ROOT_UID))
+		seq_printf(m, ",uid=%u",
+				from_kuid_munged(&init_user_ns, opts->fs_uid));
+	if (!gid_eq(opts->fs_gid, GLOBAL_ROOT_GID))
+		seq_printf(m, ",gid=%u",
+				from_kgid_munged(&init_user_ns, opts->fs_gid));
+	seq_printf(m, ",fmask=%04o", opts->fs_fmask);
+	seq_printf(m, ",dmask=%04o", opts->fs_dmask);
+	if (opts->allow_utime)
+		seq_printf(m, ",allow_utime=%04o", opts->allow_utime);
+	if (sbi->nls_disk)
+		/* strip "cp" prefix from displayed option */
+		seq_printf(m, ",codepage=%s", &sbi->nls_disk->charset[2]);
+	if (isvfat) {
+		if (sbi->nls_io)
+			seq_printf(m, ",iocharset=%s", sbi->nls_io->charset);
+
+		switch (opts->shortname) {
+		case VFAT_SFN_DISPLAY_WIN95 | VFAT_SFN_CREATE_WIN95:
+			seq_puts(m, ",shortname=win95");
+			break;
+		case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WINNT:
+			seq_puts(m, ",shortname=winnt");
+			break;
+		case VFAT_SFN_DISPLAY_WINNT | VFAT_SFN_CREATE_WIN95:
+			seq_puts(m, ",shortname=mixed");
+			break;
+		case VFAT_SFN_DISPLAY_LOWER | VFAT_SFN_CREATE_WIN95:
+			seq_puts(m, ",shortname=lower");
+			break;
+		default:
+			seq_puts(m, ",shortname=unknown");
+			break;
+		}
+	}
+	if (opts->name_check != 'n')
+		seq_printf(m, ",check=%c", opts->name_check);
+	if (opts->usefree)
+		seq_puts(m, ",usefree");
+	if (opts->quiet)
+		seq_puts(m, ",quiet");
+	if (opts->showexec)
+		seq_puts(m, ",showexec");
+	if (opts->sys_immutable)
+		seq_puts(m, ",sys_immutable");
+	if (!isvfat) {
+		if (opts->dotsOK)
+			seq_puts(m, ",dotsOK=yes");
+		if (opts->nocase)
+			seq_puts(m, ",nocase");
+	} else {
+		if (opts->utf8)
+			seq_puts(m, ",utf8");
+		if (opts->unicode_xlate)
+			seq_puts(m, ",uni_xlate");
+		if (!opts->numtail)
+			seq_puts(m, ",nonumtail");
+		if (opts->rodir)
+			seq_puts(m, ",rodir");
+	}
+	if (opts->flush)
+		seq_puts(m, ",flush");
+	if (opts->tz_set) {
+		if (opts->time_offset)
+			seq_printf(m, ",time_offset=%d", opts->time_offset);
+		else
+			seq_puts(m, ",tz=UTC");
+	}
+	if (opts->errors == FAT_ERRORS_CONT)
+		seq_puts(m, ",errors=continue");
+	else if (opts->errors == FAT_ERRORS_PANIC)
+		seq_puts(m, ",errors=panic");
+	else
+		seq_puts(m, ",errors=remount-ro");
+	if (opts->nfs == FAT_NFS_NOSTALE_RO)
+		seq_puts(m, ",nfs=nostale_ro");
+	else if (opts->nfs)
+		seq_puts(m, ",nfs=stale_rw");
+	if (opts->discard)
+		seq_puts(m, ",discard");
+	if (opts->dos1xfloppy)
+		seq_puts(m, ",dos1xfloppy");
+
+	return 0;
+}
+
+enum {
+	Opt_check_n, Opt_check_r, Opt_check_s, Opt_uid, Opt_gid,
+	Opt_umask, Opt_dmask, Opt_fmask, Opt_allow_utime, Opt_codepage,
+	Opt_usefree, Opt_nocase, Opt_quiet, Opt_showexec, Opt_debug,
+	Opt_immutable, Opt_dots, Opt_nodots,
+	Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
+	Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
+	Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
+	Opt_obsolete, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err_cont,
+	Opt_err_panic, Opt_err_ro, Opt_discard, Opt_nfs, Opt_time_offset,
+	Opt_nfs_stale_rw, Opt_nfs_nostale_ro, Opt_err, Opt_dos1xfloppy,
+};
+
+static const match_table_t fat_tokens = {
+	{Opt_check_r, "check=relaxed"},
+	{Opt_check_s, "check=strict"},
+	{Opt_check_n, "check=normal"},
+	{Opt_check_r, "check=r"},
+	{Opt_check_s, "check=s"},
+	{Opt_check_n, "check=n"},
+	{Opt_uid, "uid=%u"},
+	{Opt_gid, "gid=%u"},
+	{Opt_umask, "umask=%o"},
+	{Opt_dmask, "dmask=%o"},
+	{Opt_fmask, "fmask=%o"},
+	{Opt_allow_utime, "allow_utime=%o"},
+	{Opt_codepage, "codepage=%u"},
+	{Opt_usefree, "usefree"},
+	{Opt_nocase, "nocase"},
+	{Opt_quiet, "quiet"},
+	{Opt_showexec, "showexec"},
+	{Opt_debug, "debug"},
+	{Opt_immutable, "sys_immutable"},
+	{Opt_flush, "flush"},
+	{Opt_tz_utc, "tz=UTC"},
+	{Opt_time_offset, "time_offset=%d"},
+	{Opt_err_cont, "errors=continue"},
+	{Opt_err_panic, "errors=panic"},
+	{Opt_err_ro, "errors=remount-ro"},
+	{Opt_discard, "discard"},
+	{Opt_nfs_stale_rw, "nfs"},
+	{Opt_nfs_stale_rw, "nfs=stale_rw"},
+	{Opt_nfs_nostale_ro, "nfs=nostale_ro"},
+	{Opt_dos1xfloppy, "dos1xfloppy"},
+	{Opt_obsolete, "conv=binary"},
+	{Opt_obsolete, "conv=text"},
+	{Opt_obsolete, "conv=auto"},
+	{Opt_obsolete, "conv=b"},
+	{Opt_obsolete, "conv=t"},
+	{Opt_obsolete, "conv=a"},
+	{Opt_obsolete, "fat=%u"},
+	{Opt_obsolete, "blocksize=%u"},
+	{Opt_obsolete, "cvf_format=%20s"},
+	{Opt_obsolete, "cvf_options=%100s"},
+	{Opt_obsolete, "posix"},
+	{Opt_err, NULL},
+};
+static const match_table_t msdos_tokens = {
+	{Opt_nodots, "nodots"},
+	{Opt_nodots, "dotsOK=no"},
+	{Opt_dots, "dots"},
+	{Opt_dots, "dotsOK=yes"},
+	{Opt_err, NULL}
+};
+static const match_table_t vfat_tokens = {
+	{Opt_charset, "iocharset=%s"},
+	{Opt_shortname_lower, "shortname=lower"},
+	{Opt_shortname_win95, "shortname=win95"},
+	{Opt_shortname_winnt, "shortname=winnt"},
+	{Opt_shortname_mixed, "shortname=mixed"},
+	{Opt_utf8_no, "utf8=0"},		/* 0 or no or false */
+	{Opt_utf8_no, "utf8=no"},
+	{Opt_utf8_no, "utf8=false"},
+	{Opt_utf8_yes, "utf8=1"},		/* empty or 1 or yes or true */
+	{Opt_utf8_yes, "utf8=yes"},
+	{Opt_utf8_yes, "utf8=true"},
+	{Opt_utf8_yes, "utf8"},
+	{Opt_uni_xl_no, "uni_xlate=0"},		/* 0 or no or false */
+	{Opt_uni_xl_no, "uni_xlate=no"},
+	{Opt_uni_xl_no, "uni_xlate=false"},
+	{Opt_uni_xl_yes, "uni_xlate=1"},	/* empty or 1 or yes or true */
+	{Opt_uni_xl_yes, "uni_xlate=yes"},
+	{Opt_uni_xl_yes, "uni_xlate=true"},
+	{Opt_uni_xl_yes, "uni_xlate"},
+	{Opt_nonumtail_no, "nonumtail=0"},	/* 0 or no or false */
+	{Opt_nonumtail_no, "nonumtail=no"},
+	{Opt_nonumtail_no, "nonumtail=false"},
+	{Opt_nonumtail_yes, "nonumtail=1"},	/* empty or 1 or yes or true */
+	{Opt_nonumtail_yes, "nonumtail=yes"},
+	{Opt_nonumtail_yes, "nonumtail=true"},
+	{Opt_nonumtail_yes, "nonumtail"},
+	{Opt_rodir, "rodir"},
+	{Opt_err, NULL}
+};
+
+static int parse_options(struct super_block *sb, char *options, int is_vfat,
+			 int silent, int *debug, struct fat_mount_options *opts)
+{
+	char *p;
+	substring_t args[MAX_OPT_ARGS];
+	int option;
+	char *iocharset;
+
+	opts->isvfat = is_vfat;
+
+	opts->fs_uid = current_uid();
+	opts->fs_gid = current_gid();
+	opts->fs_fmask = opts->fs_dmask = current_umask();
+	opts->allow_utime = -1;
+	opts->codepage = fat_default_codepage;
+	fat_reset_iocharset(opts);
+	if (is_vfat) {
+		opts->shortname = VFAT_SFN_DISPLAY_WINNT|VFAT_SFN_CREATE_WIN95;
+		opts->rodir = 0;
+	} else {
+		opts->shortname = 0;
+		opts->rodir = 1;
+	}
+	opts->name_check = 'n';
+	opts->quiet = opts->showexec = opts->sys_immutable = opts->dotsOK =  0;
+	opts->unicode_xlate = 0;
+	opts->numtail = 1;
+	opts->usefree = opts->nocase = 0;
+	opts->tz_set = 0;
+	opts->nfs = 0;
+	opts->errors = FAT_ERRORS_RO;
+	*debug = 0;
+
+	opts->utf8 = IS_ENABLED(CONFIG_FAT_DEFAULT_UTF8) && is_vfat;
+
+	if (!options)
+		goto out;
+
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+		if (!*p)
+			continue;
+
+		token = match_token(p, fat_tokens, args);
+		if (token == Opt_err) {
+			if (is_vfat)
+				token = match_token(p, vfat_tokens, args);
+			else
+				token = match_token(p, msdos_tokens, args);
+		}
+		switch (token) {
+		case Opt_check_s:
+			opts->name_check = 's';
+			break;
+		case Opt_check_r:
+			opts->name_check = 'r';
+			break;
+		case Opt_check_n:
+			opts->name_check = 'n';
+			break;
+		case Opt_usefree:
+			opts->usefree = 1;
+			break;
+		case Opt_nocase:
+			if (!is_vfat)
+				opts->nocase = 1;
+			else {
+				/* for backward compatibility */
+				opts->shortname = VFAT_SFN_DISPLAY_WIN95
+					| VFAT_SFN_CREATE_WIN95;
+			}
+			break;
+		case Opt_quiet:
+			opts->quiet = 1;
+			break;
+		case Opt_showexec:
+			opts->showexec = 1;
+			break;
+		case Opt_debug:
+			*debug = 1;
+			break;
+		case Opt_immutable:
+			opts->sys_immutable = 1;
+			break;
+		case Opt_uid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			opts->fs_uid = make_kuid(current_user_ns(), option);
+			if (!uid_valid(opts->fs_uid))
+				return -EINVAL;
+			break;
+		case Opt_gid:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			opts->fs_gid = make_kgid(current_user_ns(), option);
+			if (!gid_valid(opts->fs_gid))
+				return -EINVAL;
+			break;
+		case Opt_umask:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->fs_fmask = opts->fs_dmask = option;
+			break;
+		case Opt_dmask:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->fs_dmask = option;
+			break;
+		case Opt_fmask:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->fs_fmask = option;
+			break;
+		case Opt_allow_utime:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->allow_utime = option & (S_IWGRP | S_IWOTH);
+			break;
+		case Opt_codepage:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			opts->codepage = option;
+			break;
+		case Opt_flush:
+			opts->flush = 1;
+			break;
+		case Opt_time_offset:
+			if (match_int(&args[0], &option))
+				return -EINVAL;
+			/*
+			 * GMT+-12 zones may have DST corrections so at least
+			 * 13 hours difference is needed. Make the limit 24
+			 * just in case someone invents something unusual.
+			 */
+			if (option < -24 * 60 || option > 24 * 60)
+				return -EINVAL;
+			opts->tz_set = 1;
+			opts->time_offset = option;
+			break;
+		case Opt_tz_utc:
+			opts->tz_set = 1;
+			opts->time_offset = 0;
+			break;
+		case Opt_err_cont:
+			opts->errors = FAT_ERRORS_CONT;
+			break;
+		case Opt_err_panic:
+			opts->errors = FAT_ERRORS_PANIC;
+			break;
+		case Opt_err_ro:
+			opts->errors = FAT_ERRORS_RO;
+			break;
+		case Opt_nfs_stale_rw:
+			opts->nfs = FAT_NFS_STALE_RW;
+			break;
+		case Opt_nfs_nostale_ro:
+			opts->nfs = FAT_NFS_NOSTALE_RO;
+			break;
+		case Opt_dos1xfloppy:
+			opts->dos1xfloppy = 1;
+			break;
+
+		/* msdos specific */
+		case Opt_dots:
+			opts->dotsOK = 1;
+			break;
+		case Opt_nodots:
+			opts->dotsOK = 0;
+			break;
+
+		/* vfat specific */
+		case Opt_charset:
+			fat_reset_iocharset(opts);
+			iocharset = match_strdup(&args[0]);
+			if (!iocharset)
+				return -ENOMEM;
+			opts->iocharset = iocharset;
+			break;
+		case Opt_shortname_lower:
+			opts->shortname = VFAT_SFN_DISPLAY_LOWER
+					| VFAT_SFN_CREATE_WIN95;
+			break;
+		case Opt_shortname_win95:
+			opts->shortname = VFAT_SFN_DISPLAY_WIN95
+					| VFAT_SFN_CREATE_WIN95;
+			break;
+		case Opt_shortname_winnt:
+			opts->shortname = VFAT_SFN_DISPLAY_WINNT
+					| VFAT_SFN_CREATE_WINNT;
+			break;
+		case Opt_shortname_mixed:
+			opts->shortname = VFAT_SFN_DISPLAY_WINNT
+					| VFAT_SFN_CREATE_WIN95;
+			break;
+		case Opt_utf8_no:		/* 0 or no or false */
+			opts->utf8 = 0;
+			break;
+		case Opt_utf8_yes:		/* empty or 1 or yes or true */
+			opts->utf8 = 1;
+			break;
+		case Opt_uni_xl_no:		/* 0 or no or false */
+			opts->unicode_xlate = 0;
+			break;
+		case Opt_uni_xl_yes:		/* empty or 1 or yes or true */
+			opts->unicode_xlate = 1;
+			break;
+		case Opt_nonumtail_no:		/* 0 or no or false */
+			opts->numtail = 1;	/* negated option */
+			break;
+		case Opt_nonumtail_yes:		/* empty or 1 or yes or true */
+			opts->numtail = 0;	/* negated option */
+			break;
+		case Opt_rodir:
+			opts->rodir = 1;
+			break;
+		case Opt_discard:
+			opts->discard = 1;
+			break;
+
+		/* obsolete mount options */
+		case Opt_obsolete:
+			fat_msg(sb, KERN_INFO, "\"%s\" option is obsolete, "
+			       "not supported now", p);
+			break;
+		/* unknown option */
+		default:
+			if (!silent) {
+				fat_msg(sb, KERN_ERR,
+				       "Unrecognized mount option \"%s\" "
+				       "or missing value", p);
+			}
+			return -EINVAL;
+		}
+	}
+
+out:
+	/* UTF-8 doesn't provide FAT semantics */
+	if (!strcmp(opts->iocharset, "utf8")) {
+		fat_msg(sb, KERN_WARNING, "utf8 is not a recommended IO charset"
+		       " for FAT filesystems, filesystem will be "
+		       "case sensitive!");
+	}
+
+	/* If user doesn't specify allow_utime, it's initialized from dmask. */
+	if (opts->allow_utime == (unsigned short)-1)
+		opts->allow_utime = ~opts->fs_dmask & (S_IWGRP | S_IWOTH);
+	if (opts->unicode_xlate)
+		opts->utf8 = 0;
+	if (opts->nfs == FAT_NFS_NOSTALE_RO) {
+		sb->s_flags |= SB_RDONLY;
+		sb->s_export_op = &fat_export_ops_nostale;
+	}
+
+	return 0;
+}
+
+static int fat_read_root(struct inode *inode)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	int error;
+
+	MSDOS_I(inode)->i_pos = MSDOS_ROOT_INO;
+	inode->i_uid = sbi->options.fs_uid;
+	inode->i_gid = sbi->options.fs_gid;
+	inode_inc_iversion(inode);
+	inode->i_generation = 0;
+	inode->i_mode = fat_make_mode(sbi, ATTR_DIR, S_IRWXUGO);
+	inode->i_op = sbi->dir_ops;
+	inode->i_fop = &fat_dir_operations;
+	if (is_fat32(sbi)) {
+		MSDOS_I(inode)->i_start = sbi->root_cluster;
+		error = fat_calc_dir_size(inode);
+		if (error < 0)
+			return error;
+	} else {
+		MSDOS_I(inode)->i_start = 0;
+		inode->i_size = sbi->dir_entries * sizeof(struct msdos_dir_entry);
+	}
+	inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
+			   & ~((loff_t)sbi->cluster_size - 1)) >> 9;
+	MSDOS_I(inode)->i_logstart = 0;
+	MSDOS_I(inode)->mmu_private = inode->i_size;
+
+	fat_save_attrs(inode, ATTR_DIR);
+	inode->i_mtime.tv_sec = inode->i_atime.tv_sec = inode->i_ctime.tv_sec = 0;
+	inode->i_mtime.tv_nsec = inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec = 0;
+	set_nlink(inode, fat_subdirs(inode)+2);
+
+	return 0;
+}
+
+static unsigned long calc_fat_clusters(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	/* Divide first to avoid overflow */
+	if (!is_fat12(sbi)) {
+		unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits;
+		return ent_per_sec * sbi->fat_length;
+	}
+
+	return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
+}
+
+static bool fat_bpb_is_zero(struct fat_boot_sector *b)
+{
+	if (get_unaligned_le16(&b->sector_size))
+		return false;
+	if (b->sec_per_clus)
+		return false;
+	if (b->reserved)
+		return false;
+	if (b->fats)
+		return false;
+	if (get_unaligned_le16(&b->dir_entries))
+		return false;
+	if (get_unaligned_le16(&b->sectors))
+		return false;
+	if (b->media)
+		return false;
+	if (b->fat_length)
+		return false;
+	if (b->secs_track)
+		return false;
+	if (b->heads)
+		return false;
+	return true;
+}
+
+static int fat_read_bpb(struct super_block *sb, struct fat_boot_sector *b,
+	int silent, struct fat_bios_param_block *bpb)
+{
+	int error = -EINVAL;
+
+	/* Read in BPB ... */
+	memset(bpb, 0, sizeof(*bpb));
+	bpb->fat_sector_size = get_unaligned_le16(&b->sector_size);
+	bpb->fat_sec_per_clus = b->sec_per_clus;
+	bpb->fat_reserved = le16_to_cpu(b->reserved);
+	bpb->fat_fats = b->fats;
+	bpb->fat_dir_entries = get_unaligned_le16(&b->dir_entries);
+	bpb->fat_sectors = get_unaligned_le16(&b->sectors);
+	bpb->fat_fat_length = le16_to_cpu(b->fat_length);
+	bpb->fat_total_sect = le32_to_cpu(b->total_sect);
+
+	bpb->fat16_state = b->fat16.state;
+	bpb->fat16_vol_id = get_unaligned_le32(b->fat16.vol_id);
+
+	bpb->fat32_length = le32_to_cpu(b->fat32.length);
+	bpb->fat32_root_cluster = le32_to_cpu(b->fat32.root_cluster);
+	bpb->fat32_info_sector = le16_to_cpu(b->fat32.info_sector);
+	bpb->fat32_state = b->fat32.state;
+	bpb->fat32_vol_id = get_unaligned_le32(b->fat32.vol_id);
+
+	/* Validate this looks like a FAT filesystem BPB */
+	if (!bpb->fat_reserved) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR,
+				"bogus number of reserved sectors");
+		goto out;
+	}
+	if (!bpb->fat_fats) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "bogus number of FAT structure");
+		goto out;
+	}
+
+	/*
+	 * Earlier we checked here that b->secs_track and b->head are nonzero,
+	 * but it turns out valid FAT filesystems can have zero there.
+	 */
+
+	if (!fat_valid_media(b->media)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "invalid media value (0x%02x)",
+				(unsigned)b->media);
+		goto out;
+	}
+
+	if (!is_power_of_2(bpb->fat_sector_size)
+	    || (bpb->fat_sector_size < 512)
+	    || (bpb->fat_sector_size > 4096)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "bogus logical sector size %u",
+			       (unsigned)bpb->fat_sector_size);
+		goto out;
+	}
+
+	if (!is_power_of_2(bpb->fat_sec_per_clus)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "bogus sectors per cluster %u",
+				(unsigned)bpb->fat_sec_per_clus);
+		goto out;
+	}
+
+	if (bpb->fat_fat_length == 0 && bpb->fat32_length == 0) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "bogus number of FAT sectors");
+		goto out;
+	}
+
+	error = 0;
+
+out:
+	return error;
+}
+
+static int fat_read_static_bpb(struct super_block *sb,
+	struct fat_boot_sector *b, int silent,
+	struct fat_bios_param_block *bpb)
+{
+	static const char *notdos1x = "This doesn't look like a DOS 1.x volume";
+	sector_t bd_sects = bdev_nr_sectors(sb->s_bdev);
+	struct fat_floppy_defaults *fdefaults = NULL;
+	int error = -EINVAL;
+	unsigned i;
+
+	/* 16-bit DOS 1.x reliably wrote bootstrap short-jmp code */
+	if (b->ignored[0] != 0xeb || b->ignored[2] != 0x90) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR,
+				"%s; no bootstrapping code", notdos1x);
+		goto out;
+	}
+
+	/*
+	 * If any value in this region is non-zero, it isn't archaic
+	 * DOS.
+	 */
+	if (!fat_bpb_is_zero(b)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR,
+				"%s; DOS 2.x BPB is non-zero", notdos1x);
+		goto out;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(floppy_defaults); i++) {
+		if (floppy_defaults[i].nr_sectors == bd_sects) {
+			fdefaults = &floppy_defaults[i];
+			break;
+		}
+	}
+
+	if (fdefaults == NULL) {
+		if (!silent)
+			fat_msg(sb, KERN_WARNING,
+				"This looks like a DOS 1.x volume, but isn't a recognized floppy size (%llu sectors)",
+				(u64)bd_sects);
+		goto out;
+	}
+
+	if (!silent)
+		fat_msg(sb, KERN_INFO,
+			"This looks like a DOS 1.x volume; assuming default BPB values");
+
+	memset(bpb, 0, sizeof(*bpb));
+	bpb->fat_sector_size = SECTOR_SIZE;
+	bpb->fat_sec_per_clus = fdefaults->sec_per_clus;
+	bpb->fat_reserved = 1;
+	bpb->fat_fats = 2;
+	bpb->fat_dir_entries = fdefaults->dir_entries;
+	bpb->fat_sectors = fdefaults->nr_sectors;
+	bpb->fat_fat_length = fdefaults->fat_length;
+
+	error = 0;
+
+out:
+	return error;
+}
+
+/*
+ * Read the super block of an MS-DOS FS.
+ */
+int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
+		   void (*setup)(struct super_block *))
+{
+	struct inode *root_inode = NULL, *fat_inode = NULL;
+	struct inode *fsinfo_inode = NULL;
+	struct buffer_head *bh;
+	struct fat_bios_param_block bpb;
+	struct msdos_sb_info *sbi;
+	u16 logical_sector_size;
+	u32 total_sectors, total_clusters, fat_clusters, rootdir_sectors;
+	int debug;
+	long error;
+	char buf[50];
+	struct timespec64 ts;
+
+	/*
+	 * GFP_KERNEL is ok here, because while we do hold the
+	 * superblock lock, memory pressure can't call back into
+	 * the filesystem, since we're only just about to mount
+	 * it and have no inodes etc active!
+	 */
+	sbi = kzalloc(sizeof(struct msdos_sb_info), GFP_KERNEL);
+	if (!sbi)
+		return -ENOMEM;
+	sb->s_fs_info = sbi;
+
+	sb->s_flags |= SB_NODIRATIME;
+	sb->s_magic = MSDOS_SUPER_MAGIC;
+	sb->s_op = &fat_sops;
+	sb->s_export_op = &fat_export_ops;
+	/*
+	 * fat timestamps are complex and truncated by fat itself, so
+	 * we set 1 here to be fast
+	 */
+	sb->s_time_gran = 1;
+	mutex_init(&sbi->nfs_build_inode_lock);
+	ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,
+			     DEFAULT_RATELIMIT_BURST);
+
+	error = parse_options(sb, data, isvfat, silent, &debug, &sbi->options);
+	if (error)
+		goto out_fail;
+
+	setup(sb); /* flavour-specific stuff that needs options */
+
+	error = -EIO;
+	sb_min_blocksize(sb, 512);
+	bh = sb_bread(sb, 0);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "unable to read boot sector");
+		goto out_fail;
+	}
+
+	error = fat_read_bpb(sb, (struct fat_boot_sector *)bh->b_data, silent,
+		&bpb);
+	if (error == -EINVAL && sbi->options.dos1xfloppy)
+		error = fat_read_static_bpb(sb,
+			(struct fat_boot_sector *)bh->b_data, silent, &bpb);
+	brelse(bh);
+
+	if (error == -EINVAL)
+		goto out_invalid;
+	else if (error)
+		goto out_fail;
+
+	logical_sector_size = bpb.fat_sector_size;
+	sbi->sec_per_clus = bpb.fat_sec_per_clus;
+
+	error = -EIO;
+	if (logical_sector_size < sb->s_blocksize) {
+		fat_msg(sb, KERN_ERR, "logical sector size too small for device"
+		       " (logical sector size = %u)", logical_sector_size);
+		goto out_fail;
+	}
+
+	if (logical_sector_size > sb->s_blocksize) {
+		struct buffer_head *bh_resize;
+
+		if (!sb_set_blocksize(sb, logical_sector_size)) {
+			fat_msg(sb, KERN_ERR, "unable to set blocksize %u",
+			       logical_sector_size);
+			goto out_fail;
+		}
+
+		/* Verify that the larger boot sector is fully readable */
+		bh_resize = sb_bread(sb, 0);
+		if (bh_resize == NULL) {
+			fat_msg(sb, KERN_ERR, "unable to read boot sector"
+			       " (logical sector size = %lu)",
+			       sb->s_blocksize);
+			goto out_fail;
+		}
+		brelse(bh_resize);
+	}
+
+	mutex_init(&sbi->s_lock);
+	sbi->cluster_size = sb->s_blocksize * sbi->sec_per_clus;
+	sbi->cluster_bits = ffs(sbi->cluster_size) - 1;
+	sbi->fats = bpb.fat_fats;
+	sbi->fat_bits = 0;		/* Don't know yet */
+	sbi->fat_start = bpb.fat_reserved;
+	sbi->fat_length = bpb.fat_fat_length;
+	sbi->root_cluster = 0;
+	sbi->free_clusters = -1;	/* Don't know yet */
+	sbi->free_clus_valid = 0;
+	sbi->prev_free = FAT_START_ENT;
+	sb->s_maxbytes = 0xffffffff;
+	fat_time_fat2unix(sbi, &ts, 0, cpu_to_le16(FAT_DATE_MIN), 0);
+	sb->s_time_min = ts.tv_sec;
+
+	fat_time_fat2unix(sbi, &ts, cpu_to_le16(FAT_TIME_MAX),
+			  cpu_to_le16(FAT_DATE_MAX), 0);
+	sb->s_time_max = ts.tv_sec;
+
+	if (!sbi->fat_length && bpb.fat32_length) {
+		struct fat_boot_fsinfo *fsinfo;
+		struct buffer_head *fsinfo_bh;
+
+		/* Must be FAT32 */
+		sbi->fat_bits = 32;
+		sbi->fat_length = bpb.fat32_length;
+		sbi->root_cluster = bpb.fat32_root_cluster;
+
+		/* MC - if info_sector is 0, don't multiply by 0 */
+		sbi->fsinfo_sector = bpb.fat32_info_sector;
+		if (sbi->fsinfo_sector == 0)
+			sbi->fsinfo_sector = 1;
+
+		fsinfo_bh = sb_bread(sb, sbi->fsinfo_sector);
+		if (fsinfo_bh == NULL) {
+			fat_msg(sb, KERN_ERR, "bread failed, FSINFO block"
+			       " (sector = %lu)", sbi->fsinfo_sector);
+			goto out_fail;
+		}
+
+		fsinfo = (struct fat_boot_fsinfo *)fsinfo_bh->b_data;
+		if (!IS_FSINFO(fsinfo)) {
+			fat_msg(sb, KERN_WARNING, "Invalid FSINFO signature: "
+			       "0x%08x, 0x%08x (sector = %lu)",
+			       le32_to_cpu(fsinfo->signature1),
+			       le32_to_cpu(fsinfo->signature2),
+			       sbi->fsinfo_sector);
+		} else {
+			if (sbi->options.usefree)
+				sbi->free_clus_valid = 1;
+			sbi->free_clusters = le32_to_cpu(fsinfo->free_clusters);
+			sbi->prev_free = le32_to_cpu(fsinfo->next_cluster);
+		}
+
+		brelse(fsinfo_bh);
+	}
+
+	/* interpret volume ID as a little endian 32 bit integer */
+	if (is_fat32(sbi))
+		sbi->vol_id = bpb.fat32_vol_id;
+	else /* fat 16 or 12 */
+		sbi->vol_id = bpb.fat16_vol_id;
+
+	sbi->dir_per_block = sb->s_blocksize / sizeof(struct msdos_dir_entry);
+	sbi->dir_per_block_bits = ffs(sbi->dir_per_block) - 1;
+
+	sbi->dir_start = sbi->fat_start + sbi->fats * sbi->fat_length;
+	sbi->dir_entries = bpb.fat_dir_entries;
+	if (sbi->dir_entries & (sbi->dir_per_block - 1)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "bogus number of directory entries"
+			       " (%u)", sbi->dir_entries);
+		goto out_invalid;
+	}
+
+	rootdir_sectors = sbi->dir_entries
+		* sizeof(struct msdos_dir_entry) / sb->s_blocksize;
+	sbi->data_start = sbi->dir_start + rootdir_sectors;
+	total_sectors = bpb.fat_sectors;
+	if (total_sectors == 0)
+		total_sectors = bpb.fat_total_sect;
+
+	total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
+
+	if (!is_fat32(sbi))
+		sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
+
+	/* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
+	if (is_fat32(sbi))
+		sbi->dirty = bpb.fat32_state & FAT_STATE_DIRTY;
+	else /* fat 16 or 12 */
+		sbi->dirty = bpb.fat16_state & FAT_STATE_DIRTY;
+
+	/* check that FAT table does not overflow */
+	fat_clusters = calc_fat_clusters(sb);
+	total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
+	if (total_clusters > max_fat(sb)) {
+		if (!silent)
+			fat_msg(sb, KERN_ERR, "count of clusters too big (%u)",
+			       total_clusters);
+		goto out_invalid;
+	}
+
+	sbi->max_cluster = total_clusters + FAT_START_ENT;
+	/* check the free_clusters, it's not necessarily correct */
+	if (sbi->free_clusters != -1 && sbi->free_clusters > total_clusters)
+		sbi->free_clusters = -1;
+	/* check the prev_free, it's not necessarily correct */
+	sbi->prev_free %= sbi->max_cluster;
+	if (sbi->prev_free < FAT_START_ENT)
+		sbi->prev_free = FAT_START_ENT;
+
+	/* set up enough so that it can read an inode */
+	fat_hash_init(sb);
+	dir_hash_init(sb);
+	fat_ent_access_init(sb);
+
+	/*
+	 * The low byte of the first FAT entry must have the same value as
+	 * the media field of the boot sector. But in real world, too many
+	 * devices are writing wrong values. So, removed that validity check.
+	 *
+	 * The removed check compared the first FAT entry to a value dependent
+	 * on the media field like this:
+	 * == (0x0F00 | media), for FAT12
+	 * == (0XFF00 | media), for FAT16
+	 * == (0x0FFFFF | media), for FAT32
+	 */
+
+	error = -EINVAL;
+	sprintf(buf, "cp%d", sbi->options.codepage);
+	sbi->nls_disk = load_nls(buf);
+	if (!sbi->nls_disk) {
+		fat_msg(sb, KERN_ERR, "codepage %s not found", buf);
+		goto out_fail;
+	}
+
+	/* FIXME: utf8 is using iocharset for upper/lower conversion */
+	if (sbi->options.isvfat) {
+		sbi->nls_io = load_nls(sbi->options.iocharset);
+		if (!sbi->nls_io) {
+			fat_msg(sb, KERN_ERR, "IO charset %s not found",
+			       sbi->options.iocharset);
+			goto out_fail;
+		}
+	}
+
+	error = -ENOMEM;
+	fat_inode = new_inode(sb);
+	if (!fat_inode)
+		goto out_fail;
+	sbi->fat_inode = fat_inode;
+
+	fsinfo_inode = new_inode(sb);
+	if (!fsinfo_inode)
+		goto out_fail;
+	fsinfo_inode->i_ino = MSDOS_FSINFO_INO;
+	sbi->fsinfo_inode = fsinfo_inode;
+	insert_inode_hash(fsinfo_inode);
+
+	root_inode = new_inode(sb);
+	if (!root_inode)
+		goto out_fail;
+	root_inode->i_ino = MSDOS_ROOT_INO;
+	inode_set_iversion(root_inode, 1);
+	error = fat_read_root(root_inode);
+	if (error < 0) {
+		iput(root_inode);
+		goto out_fail;
+	}
+	error = -ENOMEM;
+	insert_inode_hash(root_inode);
+	fat_attach(root_inode, 0);
+	sb->s_root = d_make_root(root_inode);
+	if (!sb->s_root) {
+		fat_msg(sb, KERN_ERR, "get root inode failed");
+		goto out_fail;
+	}
+
+	if (sbi->options.discard && !bdev_max_discard_sectors(sb->s_bdev))
+		fat_msg(sb, KERN_WARNING,
+			"mounting with \"discard\" option, but the device does not support discard");
+
+	fat_set_state(sb, 1, 0);
+	return 0;
+
+out_invalid:
+	error = -EINVAL;
+	if (!silent)
+		fat_msg(sb, KERN_INFO, "Can't find a valid FAT filesystem");
+
+out_fail:
+	iput(fsinfo_inode);
+	iput(fat_inode);
+	unload_nls(sbi->nls_io);
+	unload_nls(sbi->nls_disk);
+	fat_reset_iocharset(&sbi->options);
+	sb->s_fs_info = NULL;
+	kfree(sbi);
+	return error;
+}
+
+EXPORT_SYMBOL_GPL(fat_fill_super);
+
+/*
+ * helper function for fat_flush_inodes.  This writes both the inode
+ * and the file data blocks, waiting for in flight data blocks before
+ * the start of the call.  It does not wait for any io started
+ * during the call
+ */
+static int writeback_inode(struct inode *inode)
+{
+
+	int ret;
+
+	/* if we used wait=1, sync_inode_metadata waits for the io for the
+	* inode to finish.  So wait=0 is sent down to sync_inode_metadata
+	* and filemap_fdatawrite is used for the data blocks
+	*/
+	ret = sync_inode_metadata(inode, 0);
+	if (!ret)
+		ret = filemap_fdatawrite(inode->i_mapping);
+	return ret;
+}
+
+/*
+ * write data and metadata corresponding to i1 and i2.  The io is
+ * started but we do not wait for any of it to finish.
+ *
+ * filemap_flush is used for the block device, so if there is a dirty
+ * page for a block already in flight, we will not wait and start the
+ * io over again
+ */
+int fat_flush_inodes(struct super_block *sb, struct inode *i1, struct inode *i2)
+{
+	int ret = 0;
+	if (!MSDOS_SB(sb)->options.flush)
+		return 0;
+	if (i1)
+		ret = writeback_inode(i1);
+	if (!ret && i2)
+		ret = writeback_inode(i2);
+	if (!ret)
+		ret = sync_blockdev_nowait(sb->s_bdev);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fat_flush_inodes);
+
+static int __init init_fat_fs(void)
+{
+	int err;
+
+	err = fat_cache_init();
+	if (err)
+		return err;
+
+	err = fat_init_inodecache();
+	if (err)
+		goto failed;
+
+	return 0;
+
+failed:
+	fat_cache_destroy();
+	return err;
+}
+
+static void __exit exit_fat_fs(void)
+{
+	fat_cache_destroy();
+	fat_destroy_inodecache();
+}
+
+module_init(init_fat_fs)
+module_exit(exit_fat_fs)
+
+MODULE_LICENSE("GPL");
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
new file mode 100644
index 000000000..7e5d6ae30
--- /dev/null
+++ b/fs/fat/misc.c
@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/misc.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
+ *		 and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
+ */
+
+#include "fat.h"
+#include <linux/iversion.h>
+
+/*
+ * fat_fs_error reports a file system problem that might indicate fa data
+ * corruption/inconsistency. Depending on 'errors' mount option the
+ * panic() is called, or error message is printed FAT and nothing is done,
+ * or filesystem is remounted read-only (default behavior).
+ * In case the file system is remounted read-only, it can be made writable
+ * again by remounting it.
+ */
+void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
+{
+	struct fat_mount_options *opts = &MSDOS_SB(sb)->options;
+	va_list args;
+	struct va_format vaf;
+
+	if (report) {
+		va_start(args, fmt);
+		vaf.fmt = fmt;
+		vaf.va = &args;
+		fat_msg(sb, KERN_ERR, "error, %pV", &vaf);
+		va_end(args);
+	}
+
+	if (opts->errors == FAT_ERRORS_PANIC)
+		panic("FAT-fs (%s): fs panic from previous error\n", sb->s_id);
+	else if (opts->errors == FAT_ERRORS_RO && !sb_rdonly(sb)) {
+		sb->s_flags |= SB_RDONLY;
+		fat_msg(sb, KERN_ERR, "Filesystem has been set read-only");
+	}
+}
+EXPORT_SYMBOL_GPL(__fat_fs_error);
+
+/**
+ * _fat_msg() - Print a preformatted FAT message based on a superblock.
+ * @sb: A pointer to a &struct super_block
+ * @level: A Kernel printk level constant
+ * @fmt: The printf-style format string to print.
+ *
+ * Everything that is not fat_fs_error() should be fat_msg().
+ *
+ * fat_msg() wraps _fat_msg() for printk indexing.
+ */
+void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	_printk(FAT_PRINTK_PREFIX "%pV\n", level, sb->s_id, &vaf);
+	va_end(args);
+}
+
+/* Flushes the number of free clusters on FAT32 */
+/* XXX: Need to write one per FSINFO block.  Currently only writes 1 */
+int fat_clusters_flush(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	struct fat_boot_fsinfo *fsinfo;
+
+	if (!is_fat32(sbi))
+		return 0;
+
+	bh = sb_bread(sb, sbi->fsinfo_sector);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "bread failed in fat_clusters_flush");
+		return -EIO;
+	}
+
+	fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
+	/* Sanity check */
+	if (!IS_FSINFO(fsinfo)) {
+		fat_msg(sb, KERN_ERR, "Invalid FSINFO signature: "
+		       "0x%08x, 0x%08x (sector = %lu)",
+		       le32_to_cpu(fsinfo->signature1),
+		       le32_to_cpu(fsinfo->signature2),
+		       sbi->fsinfo_sector);
+	} else {
+		if (sbi->free_clusters != -1)
+			fsinfo->free_clusters = cpu_to_le32(sbi->free_clusters);
+		if (sbi->prev_free != -1)
+			fsinfo->next_cluster = cpu_to_le32(sbi->prev_free);
+		mark_buffer_dirty(bh);
+	}
+	brelse(bh);
+
+	return 0;
+}
+
+/*
+ * fat_chain_add() adds a new cluster to the chain of clusters represented
+ * by inode.
+ */
+int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int ret, new_fclus, last;
+
+	/*
+	 * We must locate the last cluster of the file to add this new
+	 * one (new_dclus) to the end of the link list (the FAT).
+	 */
+	last = new_fclus = 0;
+	if (MSDOS_I(inode)->i_start) {
+		int fclus, dclus;
+
+		ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
+		if (ret < 0)
+			return ret;
+		new_fclus = fclus + 1;
+		last = dclus;
+	}
+
+	/* add new one to the last of the cluster chain */
+	if (last) {
+		struct fat_entry fatent;
+
+		fatent_init(&fatent);
+		ret = fat_ent_read(inode, &fatent, last);
+		if (ret >= 0) {
+			int wait = inode_needs_sync(inode);
+			ret = fat_ent_write(inode, &fatent, new_dclus, wait);
+			fatent_brelse(&fatent);
+		}
+		if (ret < 0)
+			return ret;
+		/*
+		 * FIXME:Although we can add this cache, fat_cache_add() is
+		 * assuming to be called after linear search with fat_cache_id.
+		 */
+//		fat_cache_add(inode, new_fclus, new_dclus);
+	} else {
+		MSDOS_I(inode)->i_start = new_dclus;
+		MSDOS_I(inode)->i_logstart = new_dclus;
+		/*
+		 * Since generic_write_sync() synchronizes regular files later,
+		 * we sync here only directories.
+		 */
+		if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode)) {
+			ret = fat_sync_inode(inode);
+			if (ret)
+				return ret;
+		} else
+			mark_inode_dirty(inode);
+	}
+	if (new_fclus != (inode->i_blocks >> (sbi->cluster_bits - 9))) {
+		fat_fs_error(sb, "clusters badly computed (%d != %llu)",
+			     new_fclus,
+			     (llu)(inode->i_blocks >> (sbi->cluster_bits - 9)));
+		fat_cache_inval_inode(inode);
+	}
+	inode->i_blocks += nr_cluster << (sbi->cluster_bits - 9);
+
+	return 0;
+}
+
+/*
+ * The epoch of FAT timestamp is 1980.
+ *     :  bits :     value
+ * date:  0 -  4: day	(1 -  31)
+ * date:  5 -  8: month	(1 -  12)
+ * date:  9 - 15: year	(0 - 127) from 1980
+ * time:  0 -  4: sec	(0 -  29) 2sec counts
+ * time:  5 - 10: min	(0 -  59)
+ * time: 11 - 15: hour	(0 -  23)
+ */
+#define SECS_PER_MIN	60
+#define SECS_PER_HOUR	(60 * 60)
+#define SECS_PER_DAY	(SECS_PER_HOUR * 24)
+/* days between 1.1.70 and 1.1.80 (2 leap days) */
+#define DAYS_DELTA	(365 * 10 + 2)
+/* 120 (2100 - 1980) isn't leap year */
+#define YEAR_2100	120
+#define IS_LEAP_YEAR(y)	(!((y) & 3) && (y) != YEAR_2100)
+
+/* Linear day numbers of the respective 1sts in non-leap years. */
+static long days_in_year[] = {
+	/* Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct  Nov  Dec */
+	0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
+};
+
+static inline int fat_tz_offset(const struct msdos_sb_info *sbi)
+{
+	return (sbi->options.tz_set ?
+	       -sbi->options.time_offset :
+	       sys_tz.tz_minuteswest) * SECS_PER_MIN;
+}
+
+/* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
+void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
+		       __le16 __time, __le16 __date, u8 time_cs)
+{
+	u16 time = le16_to_cpu(__time), date = le16_to_cpu(__date);
+	time64_t second;
+	long day, leap_day, month, year;
+
+	year  = date >> 9;
+	month = max(1, (date >> 5) & 0xf);
+	day   = max(1, date & 0x1f) - 1;
+
+	leap_day = (year + 3) / 4;
+	if (year > YEAR_2100)		/* 2100 isn't leap year */
+		leap_day--;
+	if (IS_LEAP_YEAR(year) && month > 2)
+		leap_day++;
+
+	second =  (time & 0x1f) << 1;
+	second += ((time >> 5) & 0x3f) * SECS_PER_MIN;
+	second += (time >> 11) * SECS_PER_HOUR;
+	second += (time64_t)(year * 365 + leap_day
+		   + days_in_year[month] + day
+		   + DAYS_DELTA) * SECS_PER_DAY;
+
+	second += fat_tz_offset(sbi);
+
+	if (time_cs) {
+		ts->tv_sec = second + (time_cs / 100);
+		ts->tv_nsec = (time_cs % 100) * 10000000;
+	} else {
+		ts->tv_sec = second;
+		ts->tv_nsec = 0;
+	}
+}
+
+/* Export fat_time_fat2unix() for the fat_test KUnit tests. */
+EXPORT_SYMBOL_GPL(fat_time_fat2unix);
+
+/* Convert linear UNIX date to a FAT time/date pair. */
+void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
+		       __le16 *time, __le16 *date, u8 *time_cs)
+{
+	struct tm tm;
+	time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);
+
+	/*  FAT can only support year between 1980 to 2107 */
+	if (tm.tm_year < 1980 - 1900) {
+		*time = 0;
+		*date = cpu_to_le16((0 << 9) | (1 << 5) | 1);
+		if (time_cs)
+			*time_cs = 0;
+		return;
+	}
+	if (tm.tm_year > 2107 - 1900) {
+		*time = cpu_to_le16((23 << 11) | (59 << 5) | 29);
+		*date = cpu_to_le16((127 << 9) | (12 << 5) | 31);
+		if (time_cs)
+			*time_cs = 199;
+		return;
+	}
+
+	/* from 1900 -> from 1980 */
+	tm.tm_year -= 80;
+	/* 0~11 -> 1~12 */
+	tm.tm_mon++;
+	/* 0~59 -> 0~29(2sec counts) */
+	tm.tm_sec >>= 1;
+
+	*time = cpu_to_le16(tm.tm_hour << 11 | tm.tm_min << 5 | tm.tm_sec);
+	*date = cpu_to_le16(tm.tm_year << 9 | tm.tm_mon << 5 | tm.tm_mday);
+	if (time_cs)
+		*time_cs = (ts->tv_sec & 1) * 100 + ts->tv_nsec / 10000000;
+}
+EXPORT_SYMBOL_GPL(fat_time_unix2fat);
+
+static inline struct timespec64 fat_timespec64_trunc_2secs(struct timespec64 ts)
+{
+	return (struct timespec64){ ts.tv_sec & ~1ULL, 0 };
+}
+
+/*
+ * truncate atime to 24 hour granularity (00:00:00 in local timezone)
+ */
+struct timespec64 fat_truncate_atime(const struct msdos_sb_info *sbi,
+				     const struct timespec64 *ts)
+{
+	/* to localtime */
+	time64_t seconds = ts->tv_sec - fat_tz_offset(sbi);
+	s32 remainder;
+
+	div_s64_rem(seconds, SECS_PER_DAY, &remainder);
+	/* to day boundary, and back to unix time */
+	seconds = seconds + fat_tz_offset(sbi) - remainder;
+
+	return (struct timespec64){ seconds, 0 };
+}
+
+/*
+ * truncate mtime to 2 second granularity
+ */
+struct timespec64 fat_truncate_mtime(const struct msdos_sb_info *sbi,
+				     const struct timespec64 *ts)
+{
+	return fat_timespec64_trunc_2secs(*ts);
+}
+
+/*
+ * truncate the various times with appropriate granularity:
+ *   all times in root node are always 0
+ */
+int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	struct timespec64 ts;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return 0;
+
+	if (now == NULL) {
+		now = &ts;
+		ts = current_time(inode);
+	}
+
+	if (flags & S_ATIME)
+		inode->i_atime = fat_truncate_atime(sbi, now);
+	/*
+	 * ctime and mtime share the same on-disk field, and should be
+	 * identical in memory. all mtime updates will be applied to ctime,
+	 * but ctime updates are ignored.
+	 */
+	if (flags & S_MTIME)
+		inode->i_mtime = inode->i_ctime = fat_truncate_mtime(sbi, now);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_truncate_time);
+
+int fat_update_time(struct inode *inode, struct timespec64 *now, int flags)
+{
+	int dirty_flags = 0;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return 0;
+
+	if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
+		fat_truncate_time(inode, now, flags);
+		if (inode->i_sb->s_flags & SB_LAZYTIME)
+			dirty_flags |= I_DIRTY_TIME;
+		else
+			dirty_flags |= I_DIRTY_SYNC;
+	}
+
+	if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
+		dirty_flags |= I_DIRTY_SYNC;
+
+	__mark_inode_dirty(inode, dirty_flags);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_update_time);
+
+int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
+{
+	int i, err = 0;
+
+	for (i = 0; i < nr_bhs; i++)
+		write_dirty_buffer(bhs[i], 0);
+
+	for (i = 0; i < nr_bhs; i++) {
+		wait_on_buffer(bhs[i]);
+		if (!err && !buffer_uptodate(bhs[i]))
+			err = -EIO;
+	}
+	return err;
+}
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
new file mode 100644
index 000000000..efba301d6
--- /dev/null
+++ b/fs/fat/namei_msdos.c
@@ -0,0 +1,689 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/msdos/namei.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
+ *  Rewritten for constant inumbers 1999 by Al Viro
+ */
+
+#include <linux/module.h>
+#include <linux/iversion.h>
+#include "fat.h"
+
+/* Characters that are undesirable in an MS-DOS file name */
+static unsigned char bad_chars[] = "*?<>|\"";
+static unsigned char bad_if_strict[] = "+=,; ";
+
+/***** Formats an MS-DOS file name. Rejects invalid names. */
+static int msdos_format_name(const unsigned char *name, int len,
+			     unsigned char *res, struct fat_mount_options *opts)
+	/*
+	 * name is the proposed name, len is its length, res is
+	 * the resulting name, opts->name_check is either (r)elaxed,
+	 * (n)ormal or (s)trict, opts->dotsOK allows dots at the
+	 * beginning of name (for hidden files)
+	 */
+{
+	unsigned char *walk;
+	unsigned char c;
+	int space;
+
+	if (name[0] == '.') {	/* dotfile because . and .. already done */
+		if (opts->dotsOK) {
+			/* Get rid of dot - test for it elsewhere */
+			name++;
+			len--;
+		} else
+			return -EINVAL;
+	}
+	/*
+	 * disallow names that _really_ start with a dot
+	 */
+	space = 1;
+	c = 0;
+	for (walk = res; len && walk - res < 8; walk++) {
+		c = *name++;
+		len--;
+		if (opts->name_check != 'r' && strchr(bad_chars, c))
+			return -EINVAL;
+		if (opts->name_check == 's' && strchr(bad_if_strict, c))
+			return -EINVAL;
+		if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
+			return -EINVAL;
+		if (c < ' ' || c == ':' || c == '\\')
+			return -EINVAL;
+	/*
+	 * 0xE5 is legal as a first character, but we must substitute
+	 * 0x05 because 0xE5 marks deleted files.  Yes, DOS really
+	 * does this.
+	 * It seems that Microsoft hacked DOS to support non-US
+	 * characters after the 0xE5 character was already in use to
+	 * mark deleted files.
+	 */
+		if ((res == walk) && (c == 0xE5))
+			c = 0x05;
+		if (c == '.')
+			break;
+		space = (c == ' ');
+		*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
+	}
+	if (space)
+		return -EINVAL;
+	if (opts->name_check == 's' && len && c != '.') {
+		c = *name++;
+		len--;
+		if (c != '.')
+			return -EINVAL;
+	}
+	while (c != '.' && len--)
+		c = *name++;
+	if (c == '.') {
+		while (walk - res < 8)
+			*walk++ = ' ';
+		while (len > 0 && walk - res < MSDOS_NAME) {
+			c = *name++;
+			len--;
+			if (opts->name_check != 'r' && strchr(bad_chars, c))
+				return -EINVAL;
+			if (opts->name_check == 's' &&
+			    strchr(bad_if_strict, c))
+				return -EINVAL;
+			if (c < ' ' || c == ':' || c == '\\')
+				return -EINVAL;
+			if (c == '.') {
+				if (opts->name_check == 's')
+					return -EINVAL;
+				break;
+			}
+			if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
+				return -EINVAL;
+			space = c == ' ';
+			if (!opts->nocase && c >= 'a' && c <= 'z')
+				*walk++ = c - 32;
+			else
+				*walk++ = c;
+		}
+		if (space)
+			return -EINVAL;
+		if (opts->name_check == 's' && len)
+			return -EINVAL;
+	}
+	while (walk - res < MSDOS_NAME)
+		*walk++ = ' ';
+
+	return 0;
+}
+
+/***** Locates a directory entry.  Uses unformatted name. */
+static int msdos_find(struct inode *dir, const unsigned char *name, int len,
+		      struct fat_slot_info *sinfo)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
+	unsigned char msdos_name[MSDOS_NAME];
+	int err;
+
+	err = msdos_format_name(name, len, msdos_name, &sbi->options);
+	if (err)
+		return -ENOENT;
+
+	err = fat_scan(dir, msdos_name, sinfo);
+	if (!err && sbi->options.dotsOK) {
+		if (name[0] == '.') {
+			if (!(sinfo->de->attr & ATTR_HIDDEN))
+				err = -ENOENT;
+		} else {
+			if (sinfo->de->attr & ATTR_HIDDEN)
+				err = -ENOENT;
+		}
+		if (err)
+			brelse(sinfo->bh);
+	}
+	return err;
+}
+
+/*
+ * Compute the hash for the msdos name corresponding to the dentry.
+ * Note: if the name is invalid, we leave the hash code unchanged so
+ * that the existing dentry can be used. The msdos fs routines will
+ * return ENOENT or EINVAL as appropriate.
+ */
+static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
+{
+	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
+	unsigned char msdos_name[MSDOS_NAME];
+	int error;
+
+	error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
+	if (!error)
+		qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
+	return 0;
+}
+
+/*
+ * Compare two msdos names. If either of the names are invalid,
+ * we fall back to doing the standard name comparison.
+ */
+static int msdos_cmp(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
+	unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
+	int error;
+
+	error = msdos_format_name(name->name, name->len, a_msdos_name, options);
+	if (error)
+		goto old_compare;
+	error = msdos_format_name(str, len, b_msdos_name, options);
+	if (error)
+		goto old_compare;
+	error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
+out:
+	return error;
+
+old_compare:
+	error = 1;
+	if (name->len == len)
+		error = memcmp(name->name, str, len);
+	goto out;
+}
+
+static const struct dentry_operations msdos_dentry_operations = {
+	.d_hash		= msdos_hash,
+	.d_compare	= msdos_cmp,
+};
+
+/*
+ * AV. Wrappers for FAT sb operations. Is it wise?
+ */
+
+/***** Get inode using directory and name */
+static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
+				   unsigned int flags)
+{
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	struct inode *inode;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	switch (err) {
+	case -ENOENT:
+		inode = NULL;
+		break;
+	case 0:
+		inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+		brelse(sinfo.bh);
+		break;
+	default:
+		inode = ERR_PTR(err);
+	}
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return d_splice_alias(inode, dentry);
+}
+
+/***** Creates a directory entry (name is already formatted). */
+static int msdos_add_entry(struct inode *dir, const unsigned char *name,
+			   int is_dir, int is_hid, int cluster,
+			   struct timespec64 *ts, struct fat_slot_info *sinfo)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
+	struct msdos_dir_entry de;
+	__le16 time, date;
+	int err;
+
+	memcpy(de.name, name, MSDOS_NAME);
+	de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
+	if (is_hid)
+		de.attr |= ATTR_HIDDEN;
+	de.lcase = 0;
+	fat_time_unix2fat(sbi, ts, &time, &date, NULL);
+	de.cdate = de.adate = 0;
+	de.ctime = 0;
+	de.ctime_cs = 0;
+	de.time = time;
+	de.date = date;
+	fat_set_start(&de, cluster);
+	de.size = 0;
+
+	err = fat_add_entries(dir, &de, 1, sinfo);
+	if (err)
+		return err;
+
+	fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
+	if (IS_DIRSYNC(dir))
+		(void)fat_sync_inode(dir);
+	else
+		mark_inode_dirty(dir);
+
+	return 0;
+}
+
+/***** Create a file */
+static int msdos_create(struct user_namespace *mnt_userns, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode = NULL;
+	struct fat_slot_info sinfo;
+	struct timespec64 ts;
+	unsigned char msdos_name[MSDOS_NAME];
+	int err, is_hid;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
+				msdos_name, &MSDOS_SB(sb)->options);
+	if (err)
+		goto out;
+	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
+	/* Have to do it due to foo vs. .foo conflicts */
+	if (!fat_scan(dir, msdos_name, &sinfo)) {
+		brelse(sinfo.bh);
+		err = -EINVAL;
+		goto out;
+	}
+
+	ts = current_time(dir);
+	err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
+	if (err)
+		goto out;
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		goto out;
+	}
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
+	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
+
+	d_instantiate(dentry, inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+	return err;
+}
+
+/***** Remove a directory */
+static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode = d_inode(dentry);
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = fat_dir_empty(inode);
+	if (err)
+		goto out;
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	drop_nlink(dir);
+
+	clear_nlink(inode);
+	fat_truncate_time(inode, NULL, S_CTIME);
+	fat_detach(inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+
+	return err;
+}
+
+/***** Make a directory */
+static int msdos_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode)
+{
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	struct inode *inode;
+	unsigned char msdos_name[MSDOS_NAME];
+	struct timespec64 ts;
+	int err, is_hid, cluster;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
+				msdos_name, &MSDOS_SB(sb)->options);
+	if (err)
+		goto out;
+	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
+	/* foo vs .foo situation */
+	if (!fat_scan(dir, msdos_name, &sinfo)) {
+		brelse(sinfo.bh);
+		err = -EINVAL;
+		goto out;
+	}
+
+	ts = current_time(dir);
+	cluster = fat_alloc_new_dir(dir, &ts);
+	if (cluster < 0) {
+		err = cluster;
+		goto out;
+	}
+	err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
+	if (err)
+		goto out_free;
+	inc_nlink(dir);
+
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		/* the directory was completed, just return a error */
+		goto out;
+	}
+	set_nlink(inode, 2);
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
+	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
+
+	d_instantiate(dentry, inode);
+
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	fat_flush_inodes(sb, dir, inode);
+	return 0;
+
+out_free:
+	fat_free_clusters(dir, cluster);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return err;
+}
+
+/***** Unlink a file */
+static int msdos_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct super_block *sb = inode->i_sb;
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	clear_nlink(inode);
+	fat_truncate_time(inode, NULL, S_CTIME);
+	fat_detach(inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+
+	return err;
+}
+
+static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
+			   struct dentry *old_dentry,
+			   struct inode *new_dir, unsigned char *new_name,
+			   struct dentry *new_dentry, int is_hid)
+{
+	struct buffer_head *dotdot_bh;
+	struct msdos_dir_entry *dotdot_de;
+	struct inode *old_inode, *new_inode;
+	struct fat_slot_info old_sinfo, sinfo;
+	struct timespec64 ts;
+	loff_t new_i_pos;
+	int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
+
+	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
+	old_inode = d_inode(old_dentry);
+	new_inode = d_inode(new_dentry);
+
+	err = fat_scan(old_dir, old_name, &old_sinfo);
+	if (err) {
+		err = -EIO;
+		goto out;
+	}
+
+	is_dir = S_ISDIR(old_inode->i_mode);
+	update_dotdot = (is_dir && old_dir != new_dir);
+	if (update_dotdot) {
+		if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
+			err = -EIO;
+			goto out;
+		}
+	}
+
+	old_attrs = MSDOS_I(old_inode)->i_attrs;
+	err = fat_scan(new_dir, new_name, &sinfo);
+	if (!err) {
+		if (!new_inode) {
+			/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
+			if (sinfo.de != old_sinfo.de) {
+				err = -EINVAL;
+				goto out;
+			}
+			if (is_hid)
+				MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
+			else
+				MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
+			if (IS_DIRSYNC(old_dir)) {
+				err = fat_sync_inode(old_inode);
+				if (err) {
+					MSDOS_I(old_inode)->i_attrs = old_attrs;
+					goto out;
+				}
+			} else
+				mark_inode_dirty(old_inode);
+
+			inode_inc_iversion(old_dir);
+			fat_truncate_time(old_dir, NULL, S_CTIME|S_MTIME);
+			if (IS_DIRSYNC(old_dir))
+				(void)fat_sync_inode(old_dir);
+			else
+				mark_inode_dirty(old_dir);
+			goto out;
+		}
+	}
+
+	ts = current_time(old_inode);
+	if (new_inode) {
+		if (err)
+			goto out;
+		if (is_dir) {
+			err = fat_dir_empty(new_inode);
+			if (err)
+				goto out;
+		}
+		new_i_pos = MSDOS_I(new_inode)->i_pos;
+		fat_detach(new_inode);
+	} else {
+		err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
+				      &ts, &sinfo);
+		if (err)
+			goto out;
+		new_i_pos = sinfo.i_pos;
+	}
+	inode_inc_iversion(new_dir);
+
+	fat_detach(old_inode);
+	fat_attach(old_inode, new_i_pos);
+	if (is_hid)
+		MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
+	else
+		MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
+	if (IS_DIRSYNC(new_dir)) {
+		err = fat_sync_inode(old_inode);
+		if (err)
+			goto error_inode;
+	} else
+		mark_inode_dirty(old_inode);
+
+	if (update_dotdot) {
+		fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
+		mark_buffer_dirty_inode(dotdot_bh, old_inode);
+		if (IS_DIRSYNC(new_dir)) {
+			err = sync_dirty_buffer(dotdot_bh);
+			if (err)
+				goto error_dotdot;
+		}
+		drop_nlink(old_dir);
+		if (!new_inode)
+			inc_nlink(new_dir);
+	}
+
+	err = fat_remove_entries(old_dir, &old_sinfo);	/* and releases bh */
+	old_sinfo.bh = NULL;
+	if (err)
+		goto error_dotdot;
+	inode_inc_iversion(old_dir);
+	fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
+	if (IS_DIRSYNC(old_dir))
+		(void)fat_sync_inode(old_dir);
+	else
+		mark_inode_dirty(old_dir);
+
+	if (new_inode) {
+		drop_nlink(new_inode);
+		if (is_dir)
+			drop_nlink(new_inode);
+		fat_truncate_time(new_inode, &ts, S_CTIME);
+	}
+out:
+	brelse(sinfo.bh);
+	brelse(dotdot_bh);
+	brelse(old_sinfo.bh);
+	return err;
+
+error_dotdot:
+	/* data cluster is shared, serious corruption */
+	corrupt = 1;
+
+	if (update_dotdot) {
+		fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
+		mark_buffer_dirty_inode(dotdot_bh, old_inode);
+		corrupt |= sync_dirty_buffer(dotdot_bh);
+	}
+error_inode:
+	fat_detach(old_inode);
+	fat_attach(old_inode, old_sinfo.i_pos);
+	MSDOS_I(old_inode)->i_attrs = old_attrs;
+	if (new_inode) {
+		fat_attach(new_inode, new_i_pos);
+		if (corrupt)
+			corrupt |= fat_sync_inode(new_inode);
+	} else {
+		/*
+		 * If new entry was not sharing the data cluster, it
+		 * shouldn't be serious corruption.
+		 */
+		int err2 = fat_remove_entries(new_dir, &sinfo);
+		if (corrupt)
+			corrupt |= err2;
+		sinfo.bh = NULL;
+	}
+	if (corrupt < 0) {
+		fat_fs_error(new_dir->i_sb,
+			     "%s: Filesystem corrupted (i_pos %lld)",
+			     __func__, sinfo.i_pos);
+	}
+	goto out;
+}
+
+/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
+static int msdos_rename(struct user_namespace *mnt_userns,
+			struct inode *old_dir, struct dentry *old_dentry,
+			struct inode *new_dir, struct dentry *new_dentry,
+			unsigned int flags)
+{
+	struct super_block *sb = old_dir->i_sb;
+	unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
+	int err, is_hid;
+
+	if (flags & ~RENAME_NOREPLACE)
+		return -EINVAL;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(old_dentry->d_name.name,
+				old_dentry->d_name.len, old_msdos_name,
+				&MSDOS_SB(old_dir->i_sb)->options);
+	if (err)
+		goto out;
+	err = msdos_format_name(new_dentry->d_name.name,
+				new_dentry->d_name.len, new_msdos_name,
+				&MSDOS_SB(new_dir->i_sb)->options);
+	if (err)
+		goto out;
+
+	is_hid =
+	     (new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');
+
+	err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
+			      new_dir, new_msdos_name, new_dentry, is_hid);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, old_dir, new_dir);
+	return err;
+}
+
+static const struct inode_operations msdos_dir_inode_operations = {
+	.create		= msdos_create,
+	.lookup		= msdos_lookup,
+	.unlink		= msdos_unlink,
+	.mkdir		= msdos_mkdir,
+	.rmdir		= msdos_rmdir,
+	.rename		= msdos_rename,
+	.setattr	= fat_setattr,
+	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
+};
+
+static void setup(struct super_block *sb)
+{
+	MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
+	sb->s_d_op = &msdos_dentry_operations;
+	sb->s_flags |= SB_NOATIME;
+}
+
+static int msdos_fill_super(struct super_block *sb, void *data, int silent)
+{
+	return fat_fill_super(sb, data, silent, 0, setup);
+}
+
+static struct dentry *msdos_mount(struct file_system_type *fs_type,
+			int flags, const char *dev_name,
+			void *data)
+{
+	return mount_bdev(fs_type, flags, dev_name, data, msdos_fill_super);
+}
+
+static struct file_system_type msdos_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "msdos",
+	.mount		= msdos_mount,
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
+};
+MODULE_ALIAS_FS("msdos");
+
+static int __init init_msdos_fs(void)
+{
+	return register_filesystem(&msdos_fs_type);
+}
+
+static void __exit exit_msdos_fs(void)
+{
+	unregister_filesystem(&msdos_fs_type);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Werner Almesberger");
+MODULE_DESCRIPTION("MS-DOS filesystem support");
+
+module_init(init_msdos_fs)
+module_exit(exit_msdos_fs)
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
new file mode 100644
index 000000000..21620054e
--- /dev/null
+++ b/fs/fat/namei_vfat.c
@@ -0,0 +1,1234 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/vfat/namei.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  Windows95/Windows NT compatible extended MSDOS filesystem
+ *    by Gordon Chaffee Copyright (C) 1995.  Send bug reports for the
+ *    VFAT filesystem to <chaffee@cs.berkeley.edu>.  Specify
+ *    what file operation caused you trouble and if you can duplicate
+ *    the problem, send a script that demonstrates it.
+ *
+ *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
+ *
+ *  Support Multibyte characters and cleanup by
+ *				OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
+ */
+
+#include <linux/module.h>
+#include <linux/ctype.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/kernel.h>
+#include <linux/iversion.h>
+#include "fat.h"
+
+static inline unsigned long vfat_d_version(struct dentry *dentry)
+{
+	return (unsigned long) dentry->d_fsdata;
+}
+
+static inline void vfat_d_version_set(struct dentry *dentry,
+				      unsigned long version)
+{
+	dentry->d_fsdata = (void *) version;
+}
+
+/*
+ * If new entry was created in the parent, it could create the 8.3
+ * alias (the shortname of logname).  So, the parent may have the
+ * negative-dentry which matches the created 8.3 alias.
+ *
+ * If it happened, the negative dentry isn't actually negative
+ * anymore.  So, drop it.
+ */
+static int vfat_revalidate_shortname(struct dentry *dentry)
+{
+	int ret = 1;
+	spin_lock(&dentry->d_lock);
+	if (!inode_eq_iversion(d_inode(dentry->d_parent), vfat_d_version(dentry)))
+		ret = 0;
+	spin_unlock(&dentry->d_lock);
+	return ret;
+}
+
+static int vfat_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	/* This is not negative dentry. Always valid. */
+	if (d_really_is_positive(dentry))
+		return 1;
+	return vfat_revalidate_shortname(dentry);
+}
+
+static int vfat_revalidate_ci(struct dentry *dentry, unsigned int flags)
+{
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	/*
+	 * This is not negative dentry. Always valid.
+	 *
+	 * Note, rename() to existing directory entry will have ->d_inode,
+	 * and will use existing name which isn't specified name by user.
+	 *
+	 * We may be able to drop this positive dentry here. But dropping
+	 * positive dentry isn't good idea. So it's unsupported like
+	 * rename("filename", "FILENAME") for now.
+	 */
+	if (d_really_is_positive(dentry))
+		return 1;
+
+	/*
+	 * This may be nfsd (or something), anyway, we can't see the
+	 * intent of this. So, since this can be for creation, drop it.
+	 */
+	if (!flags)
+		return 0;
+
+	/*
+	 * Drop the negative dentry, in order to make sure to use the
+	 * case sensitive name which is specified by user if this is
+	 * for creation.
+	 */
+	if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
+		return 0;
+
+	return vfat_revalidate_shortname(dentry);
+}
+
+/* returns the length of a struct qstr, ignoring trailing dots */
+static unsigned int __vfat_striptail_len(unsigned int len, const char *name)
+{
+	while (len && name[len - 1] == '.')
+		len--;
+	return len;
+}
+
+static unsigned int vfat_striptail_len(const struct qstr *qstr)
+{
+	return __vfat_striptail_len(qstr->len, qstr->name);
+}
+
+/*
+ * Compute the hash for the vfat name corresponding to the dentry.
+ * Note: if the name is invalid, we leave the hash code unchanged so
+ * that the existing dentry can be used. The vfat fs routines will
+ * return ENOENT or EINVAL as appropriate.
+ */
+static int vfat_hash(const struct dentry *dentry, struct qstr *qstr)
+{
+	qstr->hash = full_name_hash(dentry, qstr->name, vfat_striptail_len(qstr));
+	return 0;
+}
+
+/*
+ * Compute the hash for the vfat name corresponding to the dentry.
+ * Note: if the name is invalid, we leave the hash code unchanged so
+ * that the existing dentry can be used. The vfat fs routines will
+ * return ENOENT or EINVAL as appropriate.
+ */
+static int vfat_hashi(const struct dentry *dentry, struct qstr *qstr)
+{
+	struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
+	const unsigned char *name;
+	unsigned int len;
+	unsigned long hash;
+
+	name = qstr->name;
+	len = vfat_striptail_len(qstr);
+
+	hash = init_name_hash(dentry);
+	while (len--)
+		hash = partial_name_hash(nls_tolower(t, *name++), hash);
+	qstr->hash = end_name_hash(hash);
+
+	return 0;
+}
+
+/*
+ * Case insensitive compare of two vfat names.
+ */
+static int vfat_cmpi(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	struct nls_table *t = MSDOS_SB(dentry->d_sb)->nls_io;
+	unsigned int alen, blen;
+
+	/* A filename cannot end in '.' or we treat it like it has none */
+	alen = vfat_striptail_len(name);
+	blen = __vfat_striptail_len(len, str);
+	if (alen == blen) {
+		if (nls_strnicmp(t, name->name, str, alen) == 0)
+			return 0;
+	}
+	return 1;
+}
+
+/*
+ * Case sensitive compare of two vfat names.
+ */
+static int vfat_cmp(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	unsigned int alen, blen;
+
+	/* A filename cannot end in '.' or we treat it like it has none */
+	alen = vfat_striptail_len(name);
+	blen = __vfat_striptail_len(len, str);
+	if (alen == blen) {
+		if (strncmp(name->name, str, alen) == 0)
+			return 0;
+	}
+	return 1;
+}
+
+static const struct dentry_operations vfat_ci_dentry_ops = {
+	.d_revalidate	= vfat_revalidate_ci,
+	.d_hash		= vfat_hashi,
+	.d_compare	= vfat_cmpi,
+};
+
+static const struct dentry_operations vfat_dentry_ops = {
+	.d_revalidate	= vfat_revalidate,
+	.d_hash		= vfat_hash,
+	.d_compare	= vfat_cmp,
+};
+
+/* Characters that are undesirable in an MS-DOS file name */
+
+static inline wchar_t vfat_bad_char(wchar_t w)
+{
+	return (w < 0x0020)
+	    || (w == '*') || (w == '?') || (w == '<') || (w == '>')
+	    || (w == '|') || (w == '"') || (w == ':') || (w == '/')
+	    || (w == '\\');
+}
+
+static inline wchar_t vfat_replace_char(wchar_t w)
+{
+	return (w == '[') || (w == ']') || (w == ';') || (w == ',')
+	    || (w == '+') || (w == '=');
+}
+
+static wchar_t vfat_skip_char(wchar_t w)
+{
+	return (w == '.') || (w == ' ');
+}
+
+static inline int vfat_is_used_badchars(const wchar_t *s, int len)
+{
+	int i;
+
+	for (i = 0; i < len; i++)
+		if (vfat_bad_char(s[i]))
+			return -EINVAL;
+
+	if (s[i - 1] == ' ') /* last character cannot be space */
+		return -EINVAL;
+
+	return 0;
+}
+
+static int vfat_find_form(struct inode *dir, unsigned char *name)
+{
+	struct fat_slot_info sinfo;
+	int err = fat_scan(dir, name, &sinfo);
+	if (err)
+		return -ENOENT;
+	brelse(sinfo.bh);
+	return 0;
+}
+
+/*
+ * 1) Valid characters for the 8.3 format alias are any combination of
+ * letters, uppercase alphabets, digits, any of the
+ * following special characters:
+ *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
+ * In this case Longfilename is not stored in disk.
+ *
+ * WinNT's Extension:
+ * File name and extension name is contain uppercase/lowercase
+ * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
+ *
+ * 2) File name is 8.3 format, but it contain the uppercase and
+ * lowercase char, muliti bytes char, etc. In this case numtail is not
+ * added, but Longfilename is stored.
+ *
+ * 3) When the one except for the above, or the following special
+ * character are contained:
+ *        .   [ ] ; , + =
+ * numtail is added, and Longfilename must be stored in disk .
+ */
+struct shortname_info {
+	unsigned char lower:1,
+		      upper:1,
+		      valid:1;
+};
+#define INIT_SHORTNAME_INFO(x)	do {		\
+	(x)->lower = 1;				\
+	(x)->upper = 1;				\
+	(x)->valid = 1;				\
+} while (0)
+
+static inline int to_shortname_char(struct nls_table *nls,
+				    unsigned char *buf, int buf_size,
+				    wchar_t *src, struct shortname_info *info)
+{
+	int len;
+
+	if (vfat_skip_char(*src)) {
+		info->valid = 0;
+		return 0;
+	}
+	if (vfat_replace_char(*src)) {
+		info->valid = 0;
+		buf[0] = '_';
+		return 1;
+	}
+
+	len = nls->uni2char(*src, buf, buf_size);
+	if (len <= 0) {
+		info->valid = 0;
+		buf[0] = '_';
+		len = 1;
+	} else if (len == 1) {
+		unsigned char prev = buf[0];
+
+		if (buf[0] >= 0x7F) {
+			info->lower = 0;
+			info->upper = 0;
+		}
+
+		buf[0] = nls_toupper(nls, buf[0]);
+		if (isalpha(buf[0])) {
+			if (buf[0] == prev)
+				info->lower = 0;
+			else
+				info->upper = 0;
+		}
+	} else {
+		info->lower = 0;
+		info->upper = 0;
+	}
+
+	return len;
+}
+
+/*
+ * Given a valid longname, create a unique shortname.  Make sure the
+ * shortname does not exist
+ * Returns negative number on error, 0 for a normal
+ * return, and 1 for valid shortname
+ */
+static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
+				 wchar_t *uname, int ulen,
+				 unsigned char *name_res, unsigned char *lcase)
+{
+	struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
+	wchar_t *ip, *ext_start, *end, *name_start;
+	unsigned char base[9], ext[4], buf[5], *p;
+	unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
+	int chl, chi;
+	int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
+	int is_shortname;
+	struct shortname_info base_info, ext_info;
+
+	is_shortname = 1;
+	INIT_SHORTNAME_INFO(&base_info);
+	INIT_SHORTNAME_INFO(&ext_info);
+
+	/* Now, we need to create a shortname from the long name */
+	ext_start = end = &uname[ulen];
+	while (--ext_start >= uname) {
+		if (*ext_start == 0x002E) {	/* is `.' */
+			if (ext_start == end - 1) {
+				sz = ulen;
+				ext_start = NULL;
+			}
+			break;
+		}
+	}
+
+	if (ext_start == uname - 1) {
+		sz = ulen;
+		ext_start = NULL;
+	} else if (ext_start) {
+		/*
+		 * Names which start with a dot could be just
+		 * an extension eg. "...test".  In this case Win95
+		 * uses the extension as the name and sets no extension.
+		 */
+		name_start = &uname[0];
+		while (name_start < ext_start) {
+			if (!vfat_skip_char(*name_start))
+				break;
+			name_start++;
+		}
+		if (name_start != ext_start) {
+			sz = ext_start - uname;
+			ext_start++;
+		} else {
+			sz = ulen;
+			ext_start = NULL;
+		}
+	}
+
+	numtail_baselen = 6;
+	numtail2_baselen = 2;
+	for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
+		chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
+					ip, &base_info);
+		if (chl == 0)
+			continue;
+
+		if (baselen < 2 && (baselen + chl) > 2)
+			numtail2_baselen = baselen;
+		if (baselen < 6 && (baselen + chl) > 6)
+			numtail_baselen = baselen;
+		for (chi = 0; chi < chl; chi++) {
+			*p++ = charbuf[chi];
+			baselen++;
+			if (baselen >= 8)
+				break;
+		}
+		if (baselen >= 8) {
+			if ((chi < chl - 1) || (ip + 1) - uname < sz)
+				is_shortname = 0;
+			break;
+		}
+	}
+	if (baselen == 0) {
+		return -EINVAL;
+	}
+
+	extlen = 0;
+	if (ext_start) {
+		for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
+			chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
+						ip, &ext_info);
+			if (chl == 0)
+				continue;
+
+			if ((extlen + chl) > 3) {
+				is_shortname = 0;
+				break;
+			}
+			for (chi = 0; chi < chl; chi++) {
+				*p++ = charbuf[chi];
+				extlen++;
+			}
+			if (extlen >= 3) {
+				if (ip + 1 != end)
+					is_shortname = 0;
+				break;
+			}
+		}
+	}
+	ext[extlen] = '\0';
+	base[baselen] = '\0';
+
+	/* Yes, it can happen. ".\xe5" would do it. */
+	if (base[0] == DELETED_FLAG)
+		base[0] = 0x05;
+
+	/* OK, at this point we know that base is not longer than 8 symbols,
+	 * ext is not longer than 3, base is nonempty, both don't contain
+	 * any bad symbols (lowercase transformed to uppercase).
+	 */
+
+	memset(name_res, ' ', MSDOS_NAME);
+	memcpy(name_res, base, baselen);
+	memcpy(name_res + 8, ext, extlen);
+	*lcase = 0;
+	if (is_shortname && base_info.valid && ext_info.valid) {
+		if (vfat_find_form(dir, name_res) == 0)
+			return -EEXIST;
+
+		if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
+			return (base_info.upper && ext_info.upper);
+		} else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
+			if ((base_info.upper || base_info.lower) &&
+			    (ext_info.upper || ext_info.lower)) {
+				if (!base_info.upper && base_info.lower)
+					*lcase |= CASE_LOWER_BASE;
+				if (!ext_info.upper && ext_info.lower)
+					*lcase |= CASE_LOWER_EXT;
+				return 1;
+			}
+			return 0;
+		} else {
+			BUG();
+		}
+	}
+
+	if (opts->numtail == 0)
+		if (vfat_find_form(dir, name_res) < 0)
+			return 0;
+
+	/*
+	 * Try to find a unique extension.  This used to
+	 * iterate through all possibilities sequentially,
+	 * but that gave extremely bad performance.  Windows
+	 * only tries a few cases before using random
+	 * values for part of the base.
+	 */
+
+	if (baselen > 6) {
+		baselen = numtail_baselen;
+		name_res[7] = ' ';
+	}
+	name_res[baselen] = '~';
+	for (i = 1; i < 10; i++) {
+		name_res[baselen + 1] = i + '0';
+		if (vfat_find_form(dir, name_res) < 0)
+			return 0;
+	}
+
+	i = jiffies;
+	sz = (jiffies >> 16) & 0x7;
+	if (baselen > 2) {
+		baselen = numtail2_baselen;
+		name_res[7] = ' ';
+	}
+	name_res[baselen + 4] = '~';
+	name_res[baselen + 5] = '1' + sz;
+	while (1) {
+		snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
+		memcpy(&name_res[baselen], buf, 4);
+		if (vfat_find_form(dir, name_res) < 0)
+			break;
+		i -= 11;
+	}
+	return 0;
+}
+
+/* Translate a string, including coded sequences into Unicode */
+static int
+xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
+	     int *longlen, int *outlen, int escape, int utf8,
+	     struct nls_table *nls)
+{
+	const unsigned char *ip;
+	unsigned char *op;
+	int i, fill;
+	int charlen;
+
+	if (utf8) {
+		*outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
+				(wchar_t *) outname, FAT_LFN_LEN + 2);
+		if (*outlen < 0)
+			return *outlen;
+		else if (*outlen > FAT_LFN_LEN)
+			return -ENAMETOOLONG;
+
+		op = &outname[*outlen * sizeof(wchar_t)];
+	} else {
+		for (i = 0, ip = name, op = outname, *outlen = 0;
+			 i < len && *outlen < FAT_LFN_LEN;
+			 *outlen += 1) {
+			if (escape && (*ip == ':')) {
+				u8 uc[2];
+
+				if (i > len - 5)
+					return -EINVAL;
+
+				if (hex2bin(uc, ip + 1, 2) < 0)
+					return -EINVAL;
+
+				*(wchar_t *)op = uc[0] << 8 | uc[1];
+
+				op += 2;
+				ip += 5;
+				i += 5;
+			} else {
+				charlen = nls->char2uni(ip, len - i,
+							(wchar_t *)op);
+				if (charlen < 0)
+					return -EINVAL;
+				ip += charlen;
+				i += charlen;
+				op += 2;
+			}
+		}
+		if (i < len)
+			return -ENAMETOOLONG;
+	}
+
+	*longlen = *outlen;
+	if (*outlen % 13) {
+		*op++ = 0;
+		*op++ = 0;
+		*outlen += 1;
+		if (*outlen % 13) {
+			fill = 13 - (*outlen % 13);
+			for (i = 0; i < fill; i++) {
+				*op++ = 0xff;
+				*op++ = 0xff;
+			}
+			*outlen += fill;
+		}
+	}
+
+	return 0;
+}
+
+static int vfat_build_slots(struct inode *dir, const unsigned char *name,
+			    int len, int is_dir, int cluster,
+			    struct timespec64 *ts,
+			    struct msdos_dir_slot *slots, int *nr_slots)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
+	struct fat_mount_options *opts = &sbi->options;
+	struct msdos_dir_slot *ps;
+	struct msdos_dir_entry *de;
+	unsigned char cksum, lcase;
+	unsigned char msdos_name[MSDOS_NAME];
+	wchar_t *uname;
+	__le16 time, date;
+	u8 time_cs;
+	int err, ulen, usize, i;
+	loff_t offset;
+
+	*nr_slots = 0;
+
+	uname = __getname();
+	if (!uname)
+		return -ENOMEM;
+
+	err = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
+			   opts->unicode_xlate, opts->utf8, sbi->nls_io);
+	if (err)
+		goto out_free;
+
+	err = vfat_is_used_badchars(uname, ulen);
+	if (err)
+		goto out_free;
+
+	err = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
+				    msdos_name, &lcase);
+	if (err < 0)
+		goto out_free;
+	else if (err == 1) {
+		de = (struct msdos_dir_entry *)slots;
+		err = 0;
+		goto shortname;
+	}
+
+	/* build the entry of long file name */
+	cksum = fat_checksum(msdos_name);
+
+	*nr_slots = usize / 13;
+	for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
+		ps->id = i;
+		ps->attr = ATTR_EXT;
+		ps->reserved = 0;
+		ps->alias_checksum = cksum;
+		ps->start = 0;
+		offset = (i - 1) * 13;
+		fatwchar_to16(ps->name0_4, uname + offset, 5);
+		fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
+		fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
+	}
+	slots[0].id |= 0x40;
+	de = (struct msdos_dir_entry *)ps;
+
+shortname:
+	/* build the entry of 8.3 alias name */
+	(*nr_slots)++;
+	memcpy(de->name, msdos_name, MSDOS_NAME);
+	de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
+	de->lcase = lcase;
+	fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
+	de->time = de->ctime = time;
+	de->date = de->cdate = de->adate = date;
+	de->ctime_cs = time_cs;
+	fat_set_start(de, cluster);
+	de->size = 0;
+out_free:
+	__putname(uname);
+	return err;
+}
+
+static int vfat_add_entry(struct inode *dir, const struct qstr *qname,
+			  int is_dir, int cluster, struct timespec64 *ts,
+			  struct fat_slot_info *sinfo)
+{
+	struct msdos_dir_slot *slots;
+	unsigned int len;
+	int err, nr_slots;
+
+	len = vfat_striptail_len(qname);
+	if (len == 0)
+		return -ENOENT;
+
+	slots = kmalloc_array(MSDOS_SLOTS, sizeof(*slots), GFP_NOFS);
+	if (slots == NULL)
+		return -ENOMEM;
+
+	err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
+			       slots, &nr_slots);
+	if (err)
+		goto cleanup;
+
+	err = fat_add_entries(dir, slots, nr_slots, sinfo);
+	if (err)
+		goto cleanup;
+
+	/* update timestamp */
+	fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
+	if (IS_DIRSYNC(dir))
+		(void)fat_sync_inode(dir);
+	else
+		mark_inode_dirty(dir);
+cleanup:
+	kfree(slots);
+	return err;
+}
+
+static int vfat_find(struct inode *dir, const struct qstr *qname,
+		     struct fat_slot_info *sinfo)
+{
+	unsigned int len = vfat_striptail_len(qname);
+	if (len == 0)
+		return -ENOENT;
+	return fat_search_long(dir, qname->name, len, sinfo);
+}
+
+static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
+				  unsigned int flags)
+{
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	struct inode *inode;
+	struct dentry *alias;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = vfat_find(dir, &dentry->d_name, &sinfo);
+	if (err) {
+		if (err == -ENOENT) {
+			inode = NULL;
+			goto out;
+		}
+		goto error;
+	}
+
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		goto error;
+	}
+
+	alias = d_find_alias(inode);
+	/*
+	 * Checking "alias->d_parent == dentry->d_parent" to make sure
+	 * FS is not corrupted (especially double linked dir).
+	 */
+	if (alias && alias->d_parent == dentry->d_parent) {
+		/*
+		 * This inode has non anonymous-DCACHE_DISCONNECTED
+		 * dentry. This means, the user did ->lookup() by an
+		 * another name (longname vs 8.3 alias of it) in past.
+		 *
+		 * Switch to new one for reason of locality if possible.
+		 */
+		if (!S_ISDIR(inode->i_mode))
+			d_move(alias, dentry);
+		iput(inode);
+		mutex_unlock(&MSDOS_SB(sb)->s_lock);
+		return alias;
+	} else
+		dput(alias);
+
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!inode)
+		vfat_d_version_set(dentry, inode_query_iversion(dir));
+	return d_splice_alias(inode, dentry);
+error:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return ERR_PTR(err);
+}
+
+static int vfat_create(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode, bool excl)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode;
+	struct fat_slot_info sinfo;
+	struct timespec64 ts;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	ts = current_time(dir);
+	err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
+	if (err)
+		goto out;
+	inode_inc_iversion(dir);
+
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		goto out;
+	}
+	inode_inc_iversion(inode);
+
+	d_instantiate(dentry, inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return err;
+}
+
+static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = fat_dir_empty(inode);
+	if (err)
+		goto out;
+	err = vfat_find(dir, &dentry->d_name, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	drop_nlink(dir);
+
+	clear_nlink(inode);
+	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
+	fat_detach(inode);
+	vfat_d_version_set(dentry, inode_query_iversion(dir));
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+
+	return err;
+}
+
+static int vfat_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = vfat_find(dir, &dentry->d_name, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	clear_nlink(inode);
+	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
+	fat_detach(inode);
+	vfat_d_version_set(dentry, inode_query_iversion(dir));
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+
+	return err;
+}
+
+static int vfat_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, umode_t mode)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode;
+	struct fat_slot_info sinfo;
+	struct timespec64 ts;
+	int err, cluster;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	ts = current_time(dir);
+	cluster = fat_alloc_new_dir(dir, &ts);
+	if (cluster < 0) {
+		err = cluster;
+		goto out;
+	}
+	err = vfat_add_entry(dir, &dentry->d_name, 1, cluster, &ts, &sinfo);
+	if (err)
+		goto out_free;
+	inode_inc_iversion(dir);
+	inc_nlink(dir);
+
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		/* the directory was completed, just return a error */
+		goto out;
+	}
+	inode_inc_iversion(inode);
+	set_nlink(inode, 2);
+
+	d_instantiate(dentry, inode);
+
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return 0;
+
+out_free:
+	fat_free_clusters(dir, cluster);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return err;
+}
+
+static int vfat_get_dotdot_de(struct inode *inode, struct buffer_head **bh,
+			      struct msdos_dir_entry **de)
+{
+	if (S_ISDIR(inode->i_mode)) {
+		if (fat_get_dotdot_entry(inode, bh, de))
+			return -EIO;
+	}
+	return 0;
+}
+
+static int vfat_sync_ipos(struct inode *dir, struct inode *inode)
+{
+	if (IS_DIRSYNC(dir))
+		return fat_sync_inode(inode);
+	mark_inode_dirty(inode);
+	return 0;
+}
+
+static int vfat_update_dotdot_de(struct inode *dir, struct inode *inode,
+				 struct buffer_head *dotdot_bh,
+				 struct msdos_dir_entry *dotdot_de)
+{
+	fat_set_start(dotdot_de, MSDOS_I(dir)->i_logstart);
+	mark_buffer_dirty_inode(dotdot_bh, inode);
+	if (IS_DIRSYNC(dir))
+		return sync_dirty_buffer(dotdot_bh);
+	return 0;
+}
+
+static void vfat_update_dir_metadata(struct inode *dir, struct timespec64 *ts)
+{
+	inode_inc_iversion(dir);
+	fat_truncate_time(dir, ts, S_CTIME | S_MTIME);
+	if (IS_DIRSYNC(dir))
+		(void)fat_sync_inode(dir);
+	else
+		mark_inode_dirty(dir);
+}
+
+static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
+		       struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct buffer_head *dotdot_bh;
+	struct msdos_dir_entry *dotdot_de = NULL;
+	struct inode *old_inode, *new_inode;
+	struct fat_slot_info old_sinfo, sinfo;
+	struct timespec64 ts;
+	loff_t new_i_pos;
+	int err, is_dir, corrupt = 0;
+	struct super_block *sb = old_dir->i_sb;
+
+	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
+	old_inode = d_inode(old_dentry);
+	new_inode = d_inode(new_dentry);
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
+	if (err)
+		goto out;
+
+	if (old_dir != new_dir) {
+		err = vfat_get_dotdot_de(old_inode, &dotdot_bh, &dotdot_de);
+		if (err)
+			goto out;
+	}
+
+	is_dir = S_ISDIR(old_inode->i_mode);
+	ts = current_time(old_dir);
+	if (new_inode) {
+		if (is_dir) {
+			err = fat_dir_empty(new_inode);
+			if (err)
+				goto out;
+		}
+		new_i_pos = MSDOS_I(new_inode)->i_pos;
+		fat_detach(new_inode);
+	} else {
+		err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
+				     &ts, &sinfo);
+		if (err)
+			goto out;
+		new_i_pos = sinfo.i_pos;
+	}
+	inode_inc_iversion(new_dir);
+
+	fat_detach(old_inode);
+	fat_attach(old_inode, new_i_pos);
+	err = vfat_sync_ipos(new_dir, old_inode);
+	if (err)
+		goto error_inode;
+
+	if (dotdot_de) {
+		err = vfat_update_dotdot_de(new_dir, old_inode, dotdot_bh,
+					    dotdot_de);
+		if (err)
+			goto error_dotdot;
+		drop_nlink(old_dir);
+		if (!new_inode)
+ 			inc_nlink(new_dir);
+	}
+
+	err = fat_remove_entries(old_dir, &old_sinfo);	/* and releases bh */
+	old_sinfo.bh = NULL;
+	if (err)
+		goto error_dotdot;
+	vfat_update_dir_metadata(old_dir, &ts);
+
+	if (new_inode) {
+		drop_nlink(new_inode);
+		if (is_dir)
+			drop_nlink(new_inode);
+		fat_truncate_time(new_inode, &ts, S_CTIME);
+	}
+out:
+	brelse(sinfo.bh);
+	brelse(dotdot_bh);
+	brelse(old_sinfo.bh);
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+
+	return err;
+
+error_dotdot:
+	/* data cluster is shared, serious corruption */
+	corrupt = 1;
+
+	if (dotdot_de) {
+		corrupt |= vfat_update_dotdot_de(old_dir, old_inode, dotdot_bh,
+						 dotdot_de);
+	}
+error_inode:
+	fat_detach(old_inode);
+	fat_attach(old_inode, old_sinfo.i_pos);
+	if (new_inode) {
+		fat_attach(new_inode, new_i_pos);
+		if (corrupt)
+			corrupt |= fat_sync_inode(new_inode);
+	} else {
+		/*
+		 * If new entry was not sharing the data cluster, it
+		 * shouldn't be serious corruption.
+		 */
+		int err2 = fat_remove_entries(new_dir, &sinfo);
+		if (corrupt)
+			corrupt |= err2;
+		sinfo.bh = NULL;
+	}
+	if (corrupt < 0) {
+		fat_fs_error(new_dir->i_sb,
+			     "%s: Filesystem corrupted (i_pos %lld)",
+			     __func__, sinfo.i_pos);
+	}
+	goto out;
+}
+
+static void vfat_exchange_ipos(struct inode *old_inode, struct inode *new_inode,
+			       loff_t old_i_pos, loff_t new_i_pos)
+{
+	fat_detach(old_inode);
+	fat_detach(new_inode);
+	fat_attach(old_inode, new_i_pos);
+	fat_attach(new_inode, old_i_pos);
+}
+
+static void vfat_move_nlink(struct inode *src, struct inode *dst)
+{
+	drop_nlink(src);
+	inc_nlink(dst);
+}
+
+static int vfat_rename_exchange(struct inode *old_dir, struct dentry *old_dentry,
+				struct inode *new_dir, struct dentry *new_dentry)
+{
+	struct buffer_head *old_dotdot_bh = NULL, *new_dotdot_bh = NULL;
+	struct msdos_dir_entry *old_dotdot_de = NULL, *new_dotdot_de = NULL;
+	struct inode *old_inode, *new_inode;
+	struct timespec64 ts = current_time(old_dir);
+	loff_t old_i_pos, new_i_pos;
+	int err, corrupt = 0;
+	struct super_block *sb = old_dir->i_sb;
+
+	old_inode = d_inode(old_dentry);
+	new_inode = d_inode(new_dentry);
+
+	/* Acquire super block lock for the operation to be atomic */
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	/* if directories are not the same, get ".." info to update */
+	if (old_dir != new_dir) {
+		err = vfat_get_dotdot_de(old_inode, &old_dotdot_bh,
+					 &old_dotdot_de);
+		if (err)
+			goto out;
+
+		err = vfat_get_dotdot_de(new_inode, &new_dotdot_bh,
+					 &new_dotdot_de);
+		if (err)
+			goto out;
+	}
+
+	old_i_pos = MSDOS_I(old_inode)->i_pos;
+	new_i_pos = MSDOS_I(new_inode)->i_pos;
+
+	vfat_exchange_ipos(old_inode, new_inode, old_i_pos, new_i_pos);
+
+	err = vfat_sync_ipos(old_dir, new_inode);
+	if (err)
+		goto error_exchange;
+	err = vfat_sync_ipos(new_dir, old_inode);
+	if (err)
+		goto error_exchange;
+
+	/* update ".." directory entry info */
+	if (old_dotdot_de) {
+		err = vfat_update_dotdot_de(new_dir, old_inode, old_dotdot_bh,
+					    old_dotdot_de);
+		if (err)
+			goto error_old_dotdot;
+	}
+	if (new_dotdot_de) {
+		err = vfat_update_dotdot_de(old_dir, new_inode, new_dotdot_bh,
+					    new_dotdot_de);
+		if (err)
+			goto error_new_dotdot;
+	}
+
+	/* if cross directory and only one is a directory, adjust nlink */
+	if (!old_dotdot_de != !new_dotdot_de) {
+		if (old_dotdot_de)
+			vfat_move_nlink(old_dir, new_dir);
+		else
+			vfat_move_nlink(new_dir, old_dir);
+	}
+
+	vfat_update_dir_metadata(old_dir, &ts);
+	/* if directories are not the same, update new_dir as well */
+	if (old_dir != new_dir)
+		vfat_update_dir_metadata(new_dir, &ts);
+
+out:
+	brelse(old_dotdot_bh);
+	brelse(new_dotdot_bh);
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+
+	return err;
+
+error_new_dotdot:
+	if (new_dotdot_de) {
+		corrupt |= vfat_update_dotdot_de(new_dir, new_inode,
+						 new_dotdot_bh, new_dotdot_de);
+	}
+
+error_old_dotdot:
+	if (old_dotdot_de) {
+		corrupt |= vfat_update_dotdot_de(old_dir, old_inode,
+						 old_dotdot_bh, old_dotdot_de);
+	}
+
+error_exchange:
+	vfat_exchange_ipos(old_inode, new_inode, new_i_pos, old_i_pos);
+	corrupt |= vfat_sync_ipos(new_dir, new_inode);
+	corrupt |= vfat_sync_ipos(old_dir, old_inode);
+
+	if (corrupt < 0) {
+		fat_fs_error(new_dir->i_sb,
+			     "%s: Filesystem corrupted (i_pos %lld, %lld)",
+			     __func__, old_i_pos, new_i_pos);
+	}
+	goto out;
+}
+
+static int vfat_rename2(struct user_namespace *mnt_userns, struct inode *old_dir,
+			struct dentry *old_dentry, struct inode *new_dir,
+			struct dentry *new_dentry, unsigned int flags)
+{
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
+		return -EINVAL;
+
+	if (flags & RENAME_EXCHANGE) {
+		return vfat_rename_exchange(old_dir, old_dentry,
+					    new_dir, new_dentry);
+	}
+
+	/* VFS already handled RENAME_NOREPLACE, handle it as a normal rename */
+	return vfat_rename(old_dir, old_dentry, new_dir, new_dentry);
+}
+
+static const struct inode_operations vfat_dir_inode_operations = {
+	.create		= vfat_create,
+	.lookup		= vfat_lookup,
+	.unlink		= vfat_unlink,
+	.mkdir		= vfat_mkdir,
+	.rmdir		= vfat_rmdir,
+	.rename		= vfat_rename2,
+	.setattr	= fat_setattr,
+	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
+};
+
+static void setup(struct super_block *sb)
+{
+	MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
+	if (MSDOS_SB(sb)->options.name_check != 's')
+		sb->s_d_op = &vfat_ci_dentry_ops;
+	else
+		sb->s_d_op = &vfat_dentry_ops;
+}
+
+static int vfat_fill_super(struct super_block *sb, void *data, int silent)
+{
+	return fat_fill_super(sb, data, silent, 1, setup);
+}
+
+static struct dentry *vfat_mount(struct file_system_type *fs_type,
+		       int flags, const char *dev_name,
+		       void *data)
+{
+	return mount_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
+}
+
+static struct file_system_type vfat_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "vfat",
+	.mount		= vfat_mount,
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
+};
+MODULE_ALIAS_FS("vfat");
+
+static int __init init_vfat_fs(void)
+{
+	return register_filesystem(&vfat_fs_type);
+}
+
+static void __exit exit_vfat_fs(void)
+{
+	unregister_filesystem(&vfat_fs_type);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("VFAT filesystem support");
+MODULE_AUTHOR("Gordon Chaffee");
+
+module_init(init_vfat_fs)
+module_exit(exit_vfat_fs)
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
new file mode 100644
index 000000000..af191371c
--- /dev/null
+++ b/fs/fat/nfs.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* fs/fat/nfs.c
+ */
+
+#include <linux/exportfs.h>
+#include "fat.h"
+
+struct fat_fid {
+	u32 i_gen;
+	u32 i_pos_low;
+	u16 i_pos_hi;
+	u16 parent_i_pos_hi;
+	u32 parent_i_pos_low;
+	u32 parent_i_gen;
+};
+
+#define FAT_FID_SIZE_WITHOUT_PARENT 3
+#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
+
+/**
+ * Look up a directory inode given its starting cluster.
+ */
+static struct inode *fat_dget(struct super_block *sb, int i_logstart)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct hlist_head *head;
+	struct msdos_inode_info *i;
+	struct inode *inode = NULL;
+
+	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
+	spin_lock(&sbi->dir_hash_lock);
+	hlist_for_each_entry(i, head, i_dir_hash) {
+		BUG_ON(i->vfs_inode.i_sb != sb);
+		if (i->i_logstart != i_logstart)
+			continue;
+		inode = igrab(&i->vfs_inode);
+		if (inode)
+			break;
+	}
+	spin_unlock(&sbi->dir_hash_lock);
+	return inode;
+}
+
+static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
+{
+	if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
+		return fat_iget(sb, i_pos);
+
+	else {
+		if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
+			return NULL;
+		return ilookup(sb, ino);
+	}
+}
+
+static struct inode *__fat_nfs_get_inode(struct super_block *sb,
+				       u64 ino, u32 generation, loff_t i_pos)
+{
+	struct inode *inode = fat_ilookup(sb, ino, i_pos);
+
+	if (inode && generation && (inode->i_generation != generation)) {
+		iput(inode);
+		inode = NULL;
+	}
+	if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
+		struct buffer_head *bh = NULL;
+		struct msdos_dir_entry *de ;
+		sector_t blocknr;
+		int offset;
+		fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
+		bh = sb_bread(sb, blocknr);
+		if (!bh) {
+			fat_msg(sb, KERN_ERR,
+				"unable to read block(%llu) for building NFS inode",
+				(llu)blocknr);
+			return inode;
+		}
+		de = (struct msdos_dir_entry *)bh->b_data;
+		/* If a file is deleted on server and client is not updated
+		 * yet, we must not build the inode upon a lookup call.
+		 */
+		if (IS_FREE(de[offset].name))
+			inode = NULL;
+		else
+			inode = fat_build_inode(sb, &de[offset], i_pos);
+		brelse(bh);
+	}
+
+	return inode;
+}
+
+static struct inode *fat_nfs_get_inode(struct super_block *sb,
+				       u64 ino, u32 generation)
+{
+
+	return __fat_nfs_get_inode(sb, ino, generation, 0);
+}
+
+static int
+fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
+		      struct inode *parent)
+{
+	int len = *lenp;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	struct fat_fid *fid = (struct fat_fid *) fh;
+	loff_t i_pos;
+	int type = FILEID_FAT_WITHOUT_PARENT;
+
+	if (parent) {
+		if (len < FAT_FID_SIZE_WITH_PARENT) {
+			*lenp = FAT_FID_SIZE_WITH_PARENT;
+			return FILEID_INVALID;
+		}
+	} else {
+		if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
+			*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
+			return FILEID_INVALID;
+		}
+	}
+
+	i_pos = fat_i_pos_read(sbi, inode);
+	*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
+	fid->i_gen = inode->i_generation;
+	fid->i_pos_low = i_pos & 0xFFFFFFFF;
+	fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
+	if (parent) {
+		i_pos = fat_i_pos_read(sbi, parent);
+		fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
+		fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
+		fid->parent_i_gen = parent->i_generation;
+		type = FILEID_FAT_WITH_PARENT;
+		*lenp = FAT_FID_SIZE_WITH_PARENT;
+	}
+
+	return type;
+}
+
+/**
+ * Map a NFS file handle to a corresponding dentry.
+ * The dentry may or may not be connected to the filesystem root.
+ */
+static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
+				int fh_len, int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    fat_nfs_get_inode);
+}
+
+static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
+					       struct fid *fh, int fh_len,
+					       int fh_type)
+{
+	struct inode *inode = NULL;
+	struct fat_fid *fid = (struct fat_fid *)fh;
+	loff_t i_pos;
+
+	switch (fh_type) {
+	case FILEID_FAT_WITHOUT_PARENT:
+		if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
+			return NULL;
+		break;
+	case FILEID_FAT_WITH_PARENT:
+		if (fh_len < FAT_FID_SIZE_WITH_PARENT)
+			return NULL;
+		break;
+	default:
+		return NULL;
+	}
+	i_pos = fid->i_pos_hi;
+	i_pos = (i_pos << 32) | (fid->i_pos_low);
+	inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
+
+	return d_obtain_alias(inode);
+}
+
+/*
+ * Find the parent for a file specified by NFS handle.
+ * This requires that the handle contain the i_ino of the parent.
+ */
+static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
+				int fh_len, int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    fat_nfs_get_inode);
+}
+
+static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
+					       struct fid *fh, int fh_len,
+					       int fh_type)
+{
+	struct inode *inode = NULL;
+	struct fat_fid *fid = (struct fat_fid *)fh;
+	loff_t i_pos;
+
+	if (fh_len < FAT_FID_SIZE_WITH_PARENT)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_FAT_WITH_PARENT:
+		i_pos = fid->parent_i_pos_hi;
+		i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
+		inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+
+/*
+ * Rebuild the parent for a directory that is not connected
+ *  to the filesystem root
+ */
+static
+struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
+{
+	int search_clus, clus_to_match;
+	struct msdos_dir_entry *de;
+	struct inode *parent = NULL;
+	struct inode *dummy_grand_parent = NULL;
+	struct fat_slot_info sinfo;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
+	struct buffer_head *parent_bh = sb_bread(sb, blknr);
+	if (!parent_bh) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read cluster of parent directory");
+		return NULL;
+	}
+
+	de = (struct msdos_dir_entry *) parent_bh->b_data;
+	clus_to_match = fat_get_start(sbi, &de[0]);
+	search_clus = fat_get_start(sbi, &de[1]);
+
+	dummy_grand_parent = fat_dget(sb, search_clus);
+	if (!dummy_grand_parent) {
+		dummy_grand_parent = new_inode(sb);
+		if (!dummy_grand_parent) {
+			brelse(parent_bh);
+			return parent;
+		}
+
+		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
+		fat_fill_inode(dummy_grand_parent, &de[1]);
+		MSDOS_I(dummy_grand_parent)->i_pos = -1;
+	}
+
+	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
+		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+
+	brelse(parent_bh);
+	iput(dummy_grand_parent);
+
+	return parent;
+}
+
+/*
+ * Find the parent for a directory that is not currently connected to
+ * the filesystem root.
+ *
+ * On entry, the caller holds d_inode(child_dir)->i_mutex.
+ */
+static struct dentry *fat_get_parent(struct dentry *child_dir)
+{
+	struct super_block *sb = child_dir->d_sb;
+	struct buffer_head *bh = NULL;
+	struct msdos_dir_entry *de;
+	struct inode *parent_inode = NULL;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) {
+		int parent_logstart = fat_get_start(sbi, de);
+		parent_inode = fat_dget(sb, parent_logstart);
+		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+			parent_inode = fat_rebuild_parent(sb, parent_logstart);
+	}
+	brelse(bh);
+
+	return d_obtain_alias(parent_inode);
+}
+
+const struct export_operations fat_export_ops = {
+	.fh_to_dentry   = fat_fh_to_dentry,
+	.fh_to_parent   = fat_fh_to_parent,
+	.get_parent     = fat_get_parent,
+};
+
+const struct export_operations fat_export_ops_nostale = {
+	.encode_fh      = fat_encode_fh_nostale,
+	.fh_to_dentry   = fat_fh_to_dentry_nostale,
+	.fh_to_parent   = fat_fh_to_parent_nostale,
+	.get_parent     = fat_get_parent,
+};