Adding upstream version 6.6.15.upstream/6.6.15

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

6 files changed, 1349 insertions, 0 deletions

diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig
new file mode 100644
index 0000000000..4612c9bbf1
--- /dev/null
+++ b/fs/cramfs/Kconfig
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config CRAMFS
+	tristate "Compressed ROM file system support (cramfs)"
+	select ZLIB_INFLATE
+	help
+	  Saying Y here includes support for CramFs (Compressed ROM File
+	  System).  CramFs is designed to be a simple, small, and compressed
+	  file system for ROM based embedded systems.  CramFs is read-only,
+	  limited to 256MB file systems (with 16MB files), and doesn't support
+	  16/32 bits uid/gid, hard links and timestamps.
+
+	  See <file:Documentation/filesystems/cramfs.rst> and
+	  <file:fs/cramfs/README> for further information.
+
+	  To compile this as a module, choose M here: the module will be called
+	  cramfs.  Note that the root file system (the one containing the
+	  directory /) cannot be compiled as a module.
+
+	  This filesystem is limited in capabilities and performance on
+	  purpose to remain small and low on RAM usage. It is most suitable
+	  for small embedded systems. If you have ample RAM to spare, you may
+	  consider a more capable compressed filesystem such as SquashFS
+	  which is much better in terms of performance and features.
+
+	  If unsure, say N.
+
+config CRAMFS_BLOCKDEV
+	bool "Support CramFs image over a regular block device" if EXPERT
+	depends on CRAMFS && BLOCK
+	default y
+	help
+	  This option allows the CramFs driver to load data from a regular
+	  block device such a disk partition or a ramdisk.
+
+config CRAMFS_MTD
+	bool "Support CramFs image directly mapped in physical memory"
+	depends on CRAMFS && CRAMFS <= MTD
+	default y if !CRAMFS_BLOCKDEV
+	help
+	  This option allows the CramFs driver to load data directly from
+	  a linear addressed memory range (usually non-volatile memory
+	  like flash) instead of going through the block device layer.
+	  This saves some memory since no intermediate buffering is
+	  necessary.
+
+	  The location of the CramFs image is determined by a
+	  MTD device capable of direct memory mapping e.g. from
+	  the 'physmap' map driver or a resulting MTD partition.
+	  For example, this would mount the cramfs image stored in
+	  the MTD partition named "xip_fs" on the /mnt mountpoint:
+
+	  mount -t cramfs mtd:xip_fs /mnt
+
+	  If unsure, say N.
diff --git a/fs/cramfs/Makefile b/fs/cramfs/Makefile
new file mode 100644
index 0000000000..8c3ed29824
--- /dev/null
+++ b/fs/cramfs/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the linux cramfs routines.
+#
+
+obj-$(CONFIG_CRAMFS) += cramfs.o
+
+cramfs-objs := inode.o uncompress.o
diff --git a/fs/cramfs/README b/fs/cramfs/README
new file mode 100644
index 0000000000..778df5c4d7
--- /dev/null
+++ b/fs/cramfs/README
@@ -0,0 +1,197 @@
+Notes on Filesystem Layout
+--------------------------
+
+These notes describe what mkcramfs generates.  Kernel requirements are
+a bit looser, e.g. it doesn't care if the <file_data> items are
+swapped around (though it does care that directory entries (inodes) in
+a given directory are contiguous, as this is used by readdir).
+
+All data is currently in host-endian format; neither mkcramfs nor the
+kernel ever do swabbing.  (See section `Block Size' below.)
+
+<filesystem>:
+	<superblock>
+	<directory_structure>
+	<data>
+
+<superblock>: struct cramfs_super (see cramfs_fs.h).
+
+<directory_structure>:
+	For each file:
+		struct cramfs_inode (see cramfs_fs.h).
+		Filename.  Not generally null-terminated, but it is
+		 null-padded to a multiple of 4 bytes.
+
+The order of inode traversal is described as "width-first" (not to be
+confused with breadth-first); i.e. like depth-first but listing all of
+a directory's entries before recursing down its subdirectories: the
+same order as `ls -AUR' (but without the /^\..*:$/ directory header
+lines); put another way, the same order as `find -type d -exec
+ls -AU1 {} \;'.
+
+Beginning in 2.4.7, directory entries are sorted.  This optimization
+allows cramfs_lookup to return more quickly when a filename does not
+exist, speeds up user-space directory sorts, etc.
+
+<data>:
+	One <file_data> for each file that's either a symlink or a
+	 regular file of non-zero st_size.
+
+<file_data>:
+	nblocks * <block_pointer>
+	 (where nblocks = (st_size - 1) / blksize + 1)
+	nblocks * <block>
+	padding to multiple of 4 bytes
+
+The i'th <block_pointer> for a file stores the byte offset of the
+*end* of the i'th <block> (i.e. one past the last byte, which is the
+same as the start of the (i+1)'th <block> if there is one).  The first
+<block> immediately follows the last <block_pointer> for the file.
+<block_pointer>s are each 32 bits long.
+
+When the CRAMFS_FLAG_EXT_BLOCK_POINTERS capability bit is set, each
+<block_pointer>'s top bits may contain special flags as follows:
+
+CRAMFS_BLK_FLAG_UNCOMPRESSED (bit 31):
+	The block data is not compressed and should be copied verbatim.
+
+CRAMFS_BLK_FLAG_DIRECT_PTR (bit 30):
+	The <block_pointer> stores the actual block start offset and not
+	its end, shifted right by 2 bits. The block must therefore be
+	aligned to a 4-byte boundary. The block size is either blksize
+	if CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified, otherwise
+	the compressed data length is included in the first 2 bytes of
+	the block data. This is used to allow discontiguous data layout
+	and specific data block alignments e.g. for XIP applications.
+
+
+The order of <file_data>'s is a depth-first descent of the directory
+tree, i.e. the same order as `find -size +0 \( -type f -o -type l \)
+-print'.
+
+
+<block>: The i'th <block> is the output of zlib's compress function
+applied to the i'th blksize-sized chunk of the input data if the
+corresponding CRAMFS_BLK_FLAG_UNCOMPRESSED <block_ptr> bit is not set,
+otherwise it is the input data directly.
+(For the last <block> of the file, the input may of course be smaller.)
+Each <block> may be a different size.  (See <block_pointer> above.)
+
+<block>s are merely byte-aligned, not generally u32-aligned.
+
+When CRAMFS_BLK_FLAG_DIRECT_PTR is specified then the corresponding
+<block> may be located anywhere and not necessarily contiguous with
+the previous/next blocks. In that case it is minimally u32-aligned.
+If CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified then the size is always
+blksize except for the last block which is limited by the file length.
+If CRAMFS_BLK_FLAG_DIRECT_PTR is set and CRAMFS_BLK_FLAG_UNCOMPRESSED
+is not set then the first 2 bytes of the block contains the size of the
+remaining block data as this cannot be determined from the placement of
+logically adjacent blocks.
+
+
+Holes
+-----
+
+This kernel supports cramfs holes (i.e. [efficient representation of]
+blocks in uncompressed data consisting entirely of NUL bytes), but by
+default mkcramfs doesn't test for & create holes, since cramfs in
+kernels up to at least 2.3.39 didn't support holes.  Run mkcramfs
+with -z if you want it to create files that can have holes in them.
+
+
+Tools
+-----
+
+The cramfs user-space tools, including mkcramfs and cramfsck, are
+located at <http://sourceforge.net/projects/cramfs/>.
+
+
+Future Development
+==================
+
+Block Size
+----------
+
+(Block size in cramfs refers to the size of input data that is
+compressed at a time.  It's intended to be somewhere around
+PAGE_SIZE for cramfs_read_folio's convenience.)
+
+The superblock ought to indicate the block size that the fs was
+written for, since comments in <linux/pagemap.h> indicate that
+PAGE_SIZE may grow in future (if I interpret the comment
+correctly).
+
+Currently, mkcramfs #define's PAGE_SIZE as 4096 and uses that
+for blksize, whereas Linux-2.3.39 uses its PAGE_SIZE, which in
+turn is defined as PAGE_SIZE (which can be as large as 32KB on arm).
+This discrepancy is a bug, though it's not clear which should be
+changed.
+
+One option is to change mkcramfs to take its PAGE_SIZE from
+<asm/page.h>.  Personally I don't like this option, but it does
+require the least amount of change: just change `#define
+PAGE_SIZE (4096)' to `#include <asm/page.h>'.  The disadvantage
+is that the generated cramfs cannot always be shared between different
+kernels, not even necessarily kernels of the same architecture if
+PAGE_SIZE is subject to change between kernel versions
+(currently possible with arm and ia64).
+
+The remaining options try to make cramfs more sharable.
+
+One part of that is addressing endianness.  The two options here are
+`always use little-endian' (like ext2fs) or `writer chooses
+endianness; kernel adapts at runtime'.  Little-endian wins because of
+code simplicity and little CPU overhead even on big-endian machines.
+
+The cost of swabbing is changing the code to use the le32_to_cpu
+etc. macros as used by ext2fs.  We don't need to swab the compressed
+data, only the superblock, inodes and block pointers.
+
+
+The other part of making cramfs more sharable is choosing a block
+size.  The options are:
+
+  1. Always 4096 bytes.
+
+  2. Writer chooses blocksize; kernel adapts but rejects blocksize >
+     PAGE_SIZE.
+
+  3. Writer chooses blocksize; kernel adapts even to blocksize >
+     PAGE_SIZE.
+
+It's easy enough to change the kernel to use a smaller value than
+PAGE_SIZE: just make cramfs_read_folio read multiple blocks.
+
+The cost of option 1 is that kernels with a larger PAGE_SIZE
+value don't get as good compression as they can.
+
+The cost of option 2 relative to option 1 is that the code uses
+variables instead of #define'd constants.  The gain is that people
+with kernels having larger PAGE_SIZE can make use of that if
+they don't mind their cramfs being inaccessible to kernels with
+smaller PAGE_SIZE values.
+
+Option 3 is easy to implement if we don't mind being CPU-inefficient:
+e.g. get read_folio to decompress to a buffer of size MAX_BLKSIZE (which
+must be no larger than 32KB) and discard what it doesn't need.
+Getting read_folio to read into all the covered pages is harder.
+
+The main advantage of option 3 over 1, 2, is better compression.  The
+cost is greater complexity.  Probably not worth it, but I hope someone
+will disagree.  (If it is implemented, then I'll re-use that code in
+e2compr.)
+
+
+Another cost of 2 and 3 over 1 is making mkcramfs use a different
+block size, but that just means adding and parsing a -b option.
+
+
+Inode Size
+----------
+
+Given that cramfs will probably be used for CDs etc. as well as just
+silicon ROMs, it might make sense to expand the inode a little from
+its current 12 bytes.  Inodes other than the root inode are followed
+by filename, so the expansion doesn't even have to be a multiple of 4
+bytes.
diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
new file mode 100644
index 0000000000..5ee7d7bbb3
--- /dev/null
+++ b/fs/cramfs/inode.c
@@ -0,0 +1,1006 @@
+/*
+ * Compressed rom filesystem for Linux.
+ *
+ * Copyright (C) 1999 Linus Torvalds.
+ *
+ * This file is released under the GPL.
+ */
+
+/*
+ * These are the VFS interfaces to the compressed rom filesystem.
+ * The actual compression is based on zlib, see the other files.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/pagemap.h>
+#include <linux/pfn_t.h>
+#include <linux/ramfs.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/blkdev.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/super.h>
+#include <linux/fs_context.h>
+#include <linux/slab.h>
+#include <linux/vfs.h>
+#include <linux/mutex.h>
+#include <uapi/linux/cramfs_fs.h>
+#include <linux/uaccess.h>
+
+#include "internal.h"
+
+/*
+ * cramfs super-block data in memory
+ */
+struct cramfs_sb_info {
+	unsigned long magic;
+	unsigned long size;
+	unsigned long blocks;
+	unsigned long files;
+	unsigned long flags;
+	void *linear_virt_addr;
+	resource_size_t linear_phys_addr;
+	size_t mtd_point_size;
+};
+
+static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+static const struct super_operations cramfs_ops;
+static const struct inode_operations cramfs_dir_inode_operations;
+static const struct file_operations cramfs_directory_operations;
+static const struct file_operations cramfs_physmem_fops;
+static const struct address_space_operations cramfs_aops;
+
+static DEFINE_MUTEX(read_mutex);
+
+
+/* These macros may change in future, to provide better st_ino semantics. */
+#define OFFSET(x)	((x)->i_ino)
+
+static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
+{
+	if (!cino->offset)
+		return offset + 1;
+	if (!cino->size)
+		return offset + 1;
+
+	/*
+	 * The file mode test fixes buggy mkcramfs implementations where
+	 * cramfs_inode->offset is set to a non zero value for entries
+	 * which did not contain data, like devices node and fifos.
+	 */
+	switch (cino->mode & S_IFMT) {
+	case S_IFREG:
+	case S_IFDIR:
+	case S_IFLNK:
+		return cino->offset << 2;
+	default:
+		break;
+	}
+	return offset + 1;
+}
+
+static struct inode *get_cramfs_inode(struct super_block *sb,
+	const struct cramfs_inode *cramfs_inode, unsigned int offset)
+{
+	struct inode *inode;
+	static struct timespec64 zerotime;
+
+	inode = iget_locked(sb, cramino(cramfs_inode, offset));
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+	if (!(inode->i_state & I_NEW))
+		return inode;
+
+	switch (cramfs_inode->mode & S_IFMT) {
+	case S_IFREG:
+		inode->i_fop = &generic_ro_fops;
+		inode->i_data.a_ops = &cramfs_aops;
+		if (IS_ENABLED(CONFIG_CRAMFS_MTD) &&
+		    CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS &&
+		    CRAMFS_SB(sb)->linear_phys_addr)
+			inode->i_fop = &cramfs_physmem_fops;
+		break;
+	case S_IFDIR:
+		inode->i_op = &cramfs_dir_inode_operations;
+		inode->i_fop = &cramfs_directory_operations;
+		break;
+	case S_IFLNK:
+		inode->i_op = &page_symlink_inode_operations;
+		inode_nohighmem(inode);
+		inode->i_data.a_ops = &cramfs_aops;
+		break;
+	default:
+		init_special_inode(inode, cramfs_inode->mode,
+				old_decode_dev(cramfs_inode->size));
+	}
+
+	inode->i_mode = cramfs_inode->mode;
+	i_uid_write(inode, cramfs_inode->uid);
+	i_gid_write(inode, cramfs_inode->gid);
+
+	/* if the lower 2 bits are zero, the inode contains data */
+	if (!(inode->i_ino & 3)) {
+		inode->i_size = cramfs_inode->size;
+		inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
+	}
+
+	/* Struct copy intentional */
+	inode->i_mtime = inode->i_atime = inode_set_ctime_to_ts(inode,
+								zerotime);
+	/* inode->i_nlink is left 1 - arguably wrong for directories,
+	   but it's the best we can do without reading the directory
+	   contents.  1 yields the right result in GNU find, even
+	   without -noleaf option. */
+
+	unlock_new_inode(inode);
+
+	return inode;
+}
+
+/*
+ * We have our own block cache: don't fill up the buffer cache
+ * with the rom-image, because the way the filesystem is set
+ * up the accesses should be fairly regular and cached in the
+ * page cache and dentry tree anyway..
+ *
+ * This also acts as a way to guarantee contiguous areas of up to
+ * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
+ * worry about end-of-buffer issues even when decompressing a full
+ * page cache.
+ *
+ * Note: This is all optimized away at compile time when
+ *       CONFIG_CRAMFS_BLOCKDEV=n.
+ */
+#define READ_BUFFERS (2)
+/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
+#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
+
+/*
+ * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
+ * data that takes up more space than the original and with unlucky
+ * alignment.
+ */
+#define BLKS_PER_BUF_SHIFT	(2)
+#define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)
+#define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_SIZE)
+
+static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
+static unsigned buffer_blocknr[READ_BUFFERS];
+static struct super_block *buffer_dev[READ_BUFFERS];
+static int next_buffer;
+
+/*
+ * Populate our block cache and return a pointer to it.
+ */
+static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
+				unsigned int len)
+{
+	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
+	struct file_ra_state ra = {};
+	struct page *pages[BLKS_PER_BUF];
+	unsigned i, blocknr, buffer;
+	unsigned long devsize;
+	char *data;
+
+	if (!len)
+		return NULL;
+	blocknr = offset >> PAGE_SHIFT;
+	offset &= PAGE_SIZE - 1;
+
+	/* Check if an existing buffer already has the data.. */
+	for (i = 0; i < READ_BUFFERS; i++) {
+		unsigned int blk_offset;
+
+		if (buffer_dev[i] != sb)
+			continue;
+		if (blocknr < buffer_blocknr[i])
+			continue;
+		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
+		blk_offset += offset;
+		if (blk_offset > BUFFER_SIZE ||
+		    blk_offset + len > BUFFER_SIZE)
+			continue;
+		return read_buffers[i] + blk_offset;
+	}
+
+	devsize = bdev_nr_bytes(sb->s_bdev) >> PAGE_SHIFT;
+
+	/* Ok, read in BLKS_PER_BUF pages completely first. */
+	file_ra_state_init(&ra, mapping);
+	page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
+
+	for (i = 0; i < BLKS_PER_BUF; i++) {
+		struct page *page = NULL;
+
+		if (blocknr + i < devsize) {
+			page = read_mapping_page(mapping, blocknr + i, NULL);
+			/* synchronous error? */
+			if (IS_ERR(page))
+				page = NULL;
+		}
+		pages[i] = page;
+	}
+
+	buffer = next_buffer;
+	next_buffer = NEXT_BUFFER(buffer);
+	buffer_blocknr[buffer] = blocknr;
+	buffer_dev[buffer] = sb;
+
+	data = read_buffers[buffer];
+	for (i = 0; i < BLKS_PER_BUF; i++) {
+		struct page *page = pages[i];
+
+		if (page) {
+			memcpy_from_page(data, page, 0, PAGE_SIZE);
+			put_page(page);
+		} else
+			memset(data, 0, PAGE_SIZE);
+		data += PAGE_SIZE;
+	}
+	return read_buffers[buffer] + offset;
+}
+
+/*
+ * Return a pointer to the linearly addressed cramfs image in memory.
+ */
+static void *cramfs_direct_read(struct super_block *sb, unsigned int offset,
+				unsigned int len)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
+
+	if (!len)
+		return NULL;
+	if (len > sbi->size || offset > sbi->size - len)
+		return page_address(ZERO_PAGE(0));
+	return sbi->linear_virt_addr + offset;
+}
+
+/*
+ * Returns a pointer to a buffer containing at least LEN bytes of
+ * filesystem starting at byte offset OFFSET into the filesystem.
+ */
+static void *cramfs_read(struct super_block *sb, unsigned int offset,
+			 unsigned int len)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
+
+	if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sbi->linear_virt_addr)
+		return cramfs_direct_read(sb, offset, len);
+	else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
+		return cramfs_blkdev_read(sb, offset, len);
+	else
+		return NULL;
+}
+
+/*
+ * For a mapping to be possible, we need a range of uncompressed and
+ * contiguous blocks. Return the offset for the first block and number of
+ * valid blocks for which that is true, or zero otherwise.
+ */
+static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
+	int i;
+	u32 *blockptrs, first_block_addr;
+
+	/*
+	 * We can dereference memory directly here as this code may be
+	 * reached only when there is a direct filesystem image mapping
+	 * available in memory.
+	 */
+	blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff * 4);
+	first_block_addr = blockptrs[0] & ~CRAMFS_BLK_FLAGS;
+	i = 0;
+	do {
+		u32 block_off = i * (PAGE_SIZE >> CRAMFS_BLK_DIRECT_PTR_SHIFT);
+		u32 expect = (first_block_addr + block_off) |
+			     CRAMFS_BLK_FLAG_DIRECT_PTR |
+			     CRAMFS_BLK_FLAG_UNCOMPRESSED;
+		if (blockptrs[i] != expect) {
+			pr_debug("range: block %d/%d got %#x expects %#x\n",
+				 pgoff+i, pgoff + *pages - 1,
+				 blockptrs[i], expect);
+			if (i == 0)
+				return 0;
+			break;
+		}
+	} while (++i < *pages);
+
+	*pages = i;
+	return first_block_addr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
+}
+
+#ifdef CONFIG_MMU
+
+/*
+ * Return true if the last page of a file in the filesystem image contains
+ * some other data that doesn't belong to that file. It is assumed that the
+ * last block is CRAMFS_BLK_FLAG_DIRECT_PTR | CRAMFS_BLK_FLAG_UNCOMPRESSED
+ * (verified by cramfs_get_block_range() and directly accessible in memory.
+ */
+static bool cramfs_last_page_is_shared(struct inode *inode)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
+	u32 partial, last_page, blockaddr, *blockptrs;
+	char *tail_data;
+
+	partial = offset_in_page(inode->i_size);
+	if (!partial)
+		return false;
+	last_page = inode->i_size >> PAGE_SHIFT;
+	blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode));
+	blockaddr = blockptrs[last_page] & ~CRAMFS_BLK_FLAGS;
+	blockaddr <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
+	tail_data = sbi->linear_virt_addr + blockaddr + partial;
+	return memchr_inv(tail_data, 0, PAGE_SIZE - partial) ? true : false;
+}
+
+static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct inode *inode = file_inode(file);
+	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
+	unsigned int pages, max_pages, offset;
+	unsigned long address, pgoff = vma->vm_pgoff;
+	char *bailout_reason;
+	int ret;
+
+	ret = generic_file_readonly_mmap(file, vma);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now try to pre-populate ptes for this vma with a direct
+	 * mapping avoiding memory allocation when possible.
+	 */
+
+	/* Could COW work here? */
+	bailout_reason = "vma is writable";
+	if (vma->vm_flags & VM_WRITE)
+		goto bailout;
+
+	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	bailout_reason = "beyond file limit";
+	if (pgoff >= max_pages)
+		goto bailout;
+	pages = min(vma_pages(vma), max_pages - pgoff);
+
+	offset = cramfs_get_block_range(inode, pgoff, &pages);
+	bailout_reason = "unsuitable block layout";
+	if (!offset)
+		goto bailout;
+	address = sbi->linear_phys_addr + offset;
+	bailout_reason = "data is not page aligned";
+	if (!PAGE_ALIGNED(address))
+		goto bailout;
+
+	/* Don't map the last page if it contains some other data */
+	if (pgoff + pages == max_pages && cramfs_last_page_is_shared(inode)) {
+		pr_debug("mmap: %pD: last page is shared\n", file);
+		pages--;
+	}
+
+	if (!pages) {
+		bailout_reason = "no suitable block remaining";
+		goto bailout;
+	}
+
+	if (pages == vma_pages(vma)) {
+		/*
+		 * The entire vma is mappable. remap_pfn_range() will
+		 * make it distinguishable from a non-direct mapping
+		 * in /proc/<pid>/maps by substituting the file offset
+		 * with the actual physical address.
+		 */
+		ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
+				      pages * PAGE_SIZE, vma->vm_page_prot);
+	} else {
+		/*
+		 * Let's create a mixed map if we can't map it all.
+		 * The normal paging machinery will take care of the
+		 * unpopulated ptes via cramfs_read_folio().
+		 */
+		int i;
+		vm_flags_set(vma, VM_MIXEDMAP);
+		for (i = 0; i < pages && !ret; i++) {
+			vm_fault_t vmf;
+			unsigned long off = i * PAGE_SIZE;
+			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
+			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
+			if (vmf & VM_FAULT_ERROR)
+				ret = vm_fault_to_errno(vmf, 0);
+		}
+	}
+
+	if (!ret)
+		pr_debug("mapped %pD[%lu] at 0x%08lx (%u/%lu pages) "
+			 "to vma 0x%08lx, page_prot 0x%llx\n", file,
+			 pgoff, address, pages, vma_pages(vma), vma->vm_start,
+			 (unsigned long long)pgprot_val(vma->vm_page_prot));
+	return ret;
+
+bailout:
+	pr_debug("%pD[%lu]: direct mmap impossible: %s\n",
+		 file, pgoff, bailout_reason);
+	/* Didn't manage any direct map, but normal paging is still possible */
+	return 0;
+}
+
+#else /* CONFIG_MMU */
+
+static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	return is_nommu_shared_mapping(vma->vm_flags) ? 0 : -ENOSYS;
+}
+
+static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
+			unsigned long addr, unsigned long len,
+			unsigned long pgoff, unsigned long flags)
+{
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
+	unsigned int pages, block_pages, max_pages, offset;
+
+	pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if (pgoff >= max_pages || pages > max_pages - pgoff)
+		return -EINVAL;
+	block_pages = pages;
+	offset = cramfs_get_block_range(inode, pgoff, &block_pages);
+	if (!offset || block_pages != pages)
+		return -ENOSYS;
+	addr = sbi->linear_phys_addr + offset;
+	pr_debug("get_unmapped for %pD ofs %#lx siz %lu at 0x%08lx\n",
+		 file, pgoff*PAGE_SIZE, len, addr);
+	return addr;
+}
+
+static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
+{
+	return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
+	       NOMMU_MAP_READ | NOMMU_MAP_EXEC;
+}
+
+#endif /* CONFIG_MMU */
+
+static const struct file_operations cramfs_physmem_fops = {
+	.llseek			= generic_file_llseek,
+	.read_iter		= generic_file_read_iter,
+	.splice_read		= filemap_splice_read,
+	.mmap			= cramfs_physmem_mmap,
+#ifndef CONFIG_MMU
+	.get_unmapped_area	= cramfs_physmem_get_unmapped_area,
+	.mmap_capabilities	= cramfs_physmem_mmap_capabilities,
+#endif
+};
+
+static void cramfs_kill_sb(struct super_block *sb)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
+
+	generic_shutdown_super(sb);
+
+	if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sb->s_mtd) {
+		if (sbi && sbi->mtd_point_size)
+			mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
+		put_mtd_device(sb->s_mtd);
+		sb->s_mtd = NULL;
+	} else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
+		sync_blockdev(sb->s_bdev);
+		blkdev_put(sb->s_bdev, sb);
+	}
+	kfree(sbi);
+}
+
+static int cramfs_reconfigure(struct fs_context *fc)
+{
+	sync_filesystem(fc->root->d_sb);
+	fc->sb_flags |= SB_RDONLY;
+	return 0;
+}
+
+static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
+			     struct cramfs_super *super)
+{
+	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
+	unsigned long root_offset;
+	bool silent = fc->sb_flags & SB_SILENT;
+
+	/* We don't know the real size yet */
+	sbi->size = PAGE_SIZE;
+
+	/* Read the first block and get the superblock from it */
+	mutex_lock(&read_mutex);
+	memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super));
+	mutex_unlock(&read_mutex);
+
+	/* Do sanity checks on the superblock */
+	if (super->magic != CRAMFS_MAGIC) {
+		/* check for wrong endianness */
+		if (super->magic == CRAMFS_MAGIC_WEND) {
+			if (!silent)
+				errorfc(fc, "wrong endianness");
+			return -EINVAL;
+		}
+
+		/* check at 512 byte offset */
+		mutex_lock(&read_mutex);
+		memcpy(super,
+		       cramfs_read(sb, 512, sizeof(*super)),
+		       sizeof(*super));
+		mutex_unlock(&read_mutex);
+		if (super->magic != CRAMFS_MAGIC) {
+			if (super->magic == CRAMFS_MAGIC_WEND && !silent)
+				errorfc(fc, "wrong endianness");
+			else if (!silent)
+				errorfc(fc, "wrong magic");
+			return -EINVAL;
+		}
+	}
+
+	/* get feature flags first */
+	if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
+		errorfc(fc, "unsupported filesystem features");
+		return -EINVAL;
+	}
+
+	/* Check that the root inode is in a sane state */
+	if (!S_ISDIR(super->root.mode)) {
+		errorfc(fc, "root is not a directory");
+		return -EINVAL;
+	}
+	/* correct strange, hard-coded permissions of mkcramfs */
+	super->root.mode |= 0555;
+
+	root_offset = super->root.offset << 2;
+	if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) {
+		sbi->size = super->size;
+		sbi->blocks = super->fsid.blocks;
+		sbi->files = super->fsid.files;
+	} else {
+		sbi->size = 1<<28;
+		sbi->blocks = 0;
+		sbi->files = 0;
+	}
+	sbi->magic = super->magic;
+	sbi->flags = super->flags;
+	if (root_offset == 0)
+		infofc(fc, "empty filesystem");
+	else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
+		 ((root_offset != sizeof(struct cramfs_super)) &&
+		  (root_offset != 512 + sizeof(struct cramfs_super))))
+	{
+		errorfc(fc, "bad root offset %lu", root_offset);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int cramfs_finalize_super(struct super_block *sb,
+				 struct cramfs_inode *cramfs_root)
+{
+	struct inode *root;
+
+	/* Set it all up.. */
+	sb->s_flags |= SB_RDONLY;
+	sb->s_time_min = 0;
+	sb->s_time_max = 0;
+	sb->s_op = &cramfs_ops;
+	root = get_cramfs_inode(sb, cramfs_root, 0);
+	if (IS_ERR(root))
+		return PTR_ERR(root);
+	sb->s_root = d_make_root(root);
+	if (!sb->s_root)
+		return -ENOMEM;
+	return 0;
+}
+
+static int cramfs_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct cramfs_sb_info *sbi;
+	struct cramfs_super super;
+	int i, err;
+
+	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
+	if (!sbi)
+		return -ENOMEM;
+	sb->s_fs_info = sbi;
+
+	/* Invalidate the read buffers on mount: think disk change.. */
+	for (i = 0; i < READ_BUFFERS; i++)
+		buffer_blocknr[i] = -1;
+
+	err = cramfs_read_super(sb, fc, &super);
+	if (err)
+		return err;
+	return cramfs_finalize_super(sb, &super.root);
+}
+
+static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct cramfs_sb_info *sbi;
+	struct cramfs_super super;
+	int err;
+
+	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
+	if (!sbi)
+		return -ENOMEM;
+	sb->s_fs_info = sbi;
+
+	/* Map only one page for now.  Will remap it when fs size is known. */
+	err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
+			&sbi->linear_virt_addr, &sbi->linear_phys_addr);
+	if (err || sbi->mtd_point_size != PAGE_SIZE) {
+		pr_err("unable to get direct memory access to mtd:%s\n",
+		       sb->s_mtd->name);
+		return err ? : -ENODATA;
+	}
+
+	pr_info("checking physical address %pap for linear cramfs image\n",
+		&sbi->linear_phys_addr);
+	err = cramfs_read_super(sb, fc, &super);
+	if (err)
+		return err;
+
+	/* Remap the whole filesystem now */
+	pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
+		sb->s_mtd->name, sbi->size/1024);
+	mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
+	err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
+			&sbi->linear_virt_addr, &sbi->linear_phys_addr);
+	if (err || sbi->mtd_point_size != sbi->size) {
+		pr_err("unable to get direct memory access to mtd:%s\n",
+		       sb->s_mtd->name);
+		return err ? : -ENODATA;
+	}
+
+	return cramfs_finalize_super(sb, &super.root);
+}
+
+static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	u64 id = 0;
+
+	if (sb->s_bdev)
+		id = huge_encode_dev(sb->s_bdev->bd_dev);
+	else if (sb->s_dev)
+		id = huge_encode_dev(sb->s_dev);
+
+	buf->f_type = CRAMFS_MAGIC;
+	buf->f_bsize = PAGE_SIZE;
+	buf->f_blocks = CRAMFS_SB(sb)->blocks;
+	buf->f_bfree = 0;
+	buf->f_bavail = 0;
+	buf->f_files = CRAMFS_SB(sb)->files;
+	buf->f_ffree = 0;
+	buf->f_fsid = u64_to_fsid(id);
+	buf->f_namelen = CRAMFS_MAXPATHLEN;
+	return 0;
+}
+
+/*
+ * Read a cramfs directory entry.
+ */
+static int cramfs_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	char *buf;
+	unsigned int offset;
+
+	/* Offset within the thing. */
+	if (ctx->pos >= inode->i_size)
+		return 0;
+	offset = ctx->pos;
+	/* Directory entries are always 4-byte aligned */
+	if (offset & 3)
+		return -EINVAL;
+
+	buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	while (offset < inode->i_size) {
+		struct cramfs_inode *de;
+		unsigned long nextoffset;
+		char *name;
+		ino_t ino;
+		umode_t mode;
+		int namelen;
+
+		mutex_lock(&read_mutex);
+		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
+		name = (char *)(de+1);
+
+		/*
+		 * Namelengths on disk are shifted by two
+		 * and the name padded out to 4-byte boundaries
+		 * with zeroes.
+		 */
+		namelen = de->namelen << 2;
+		memcpy(buf, name, namelen);
+		ino = cramino(de, OFFSET(inode) + offset);
+		mode = de->mode;
+		mutex_unlock(&read_mutex);
+		nextoffset = offset + sizeof(*de) + namelen;
+		for (;;) {
+			if (!namelen) {
+				kfree(buf);
+				return -EIO;
+			}
+			if (buf[namelen-1])
+				break;
+			namelen--;
+		}
+		if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
+			break;
+
+		ctx->pos = offset = nextoffset;
+	}
+	kfree(buf);
+	return 0;
+}
+
+/*
+ * Lookup and fill in the inode data..
+ */
+static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	unsigned int offset = 0;
+	struct inode *inode = NULL;
+	int sorted;
+
+	mutex_lock(&read_mutex);
+	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
+	while (offset < dir->i_size) {
+		struct cramfs_inode *de;
+		char *name;
+		int namelen, retval;
+		int dir_off = OFFSET(dir) + offset;
+
+		de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
+		name = (char *)(de+1);
+
+		/* Try to take advantage of sorted directories */
+		if (sorted && (dentry->d_name.name[0] < name[0]))
+			break;
+
+		namelen = de->namelen << 2;
+		offset += sizeof(*de) + namelen;
+
+		/* Quick check that the name is roughly the right length */
+		if (((dentry->d_name.len + 3) & ~3) != namelen)
+			continue;
+
+		for (;;) {
+			if (!namelen) {
+				inode = ERR_PTR(-EIO);
+				goto out;
+			}
+			if (name[namelen-1])
+				break;
+			namelen--;
+		}
+		if (namelen != dentry->d_name.len)
+			continue;
+		retval = memcmp(dentry->d_name.name, name, namelen);
+		if (retval > 0)
+			continue;
+		if (!retval) {
+			inode = get_cramfs_inode(dir->i_sb, de, dir_off);
+			break;
+		}
+		/* else (retval < 0) */
+		if (sorted)
+			break;
+	}
+out:
+	mutex_unlock(&read_mutex);
+	return d_splice_alias(inode, dentry);
+}
+
+static int cramfs_read_folio(struct file *file, struct folio *folio)
+{
+	struct page *page = &folio->page;
+	struct inode *inode = page->mapping->host;
+	u32 maxblock;
+	int bytes_filled;
+	void *pgdata;
+
+	maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	bytes_filled = 0;
+	pgdata = kmap_local_page(page);
+
+	if (page->index < maxblock) {
+		struct super_block *sb = inode->i_sb;
+		u32 blkptr_offset = OFFSET(inode) + page->index * 4;
+		u32 block_ptr, block_start, block_len;
+		bool uncompressed, direct;
+
+		mutex_lock(&read_mutex);
+		block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
+		uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
+		direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
+		block_ptr &= ~CRAMFS_BLK_FLAGS;
+
+		if (direct) {
+			/*
+			 * The block pointer is an absolute start pointer,
+			 * shifted by 2 bits. The size is included in the
+			 * first 2 bytes of the data block when compressed,
+			 * or PAGE_SIZE otherwise.
+			 */
+			block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
+			if (uncompressed) {
+				block_len = PAGE_SIZE;
+				/* if last block: cap to file length */
+				if (page->index == maxblock - 1)
+					block_len =
+						offset_in_page(inode->i_size);
+			} else {
+				block_len = *(u16 *)
+					cramfs_read(sb, block_start, 2);
+				block_start += 2;
+			}
+		} else {
+			/*
+			 * The block pointer indicates one past the end of
+			 * the current block (start of next block). If this
+			 * is the first block then it starts where the block
+			 * pointer table ends, otherwise its start comes
+			 * from the previous block's pointer.
+			 */
+			block_start = OFFSET(inode) + maxblock * 4;
+			if (page->index)
+				block_start = *(u32 *)
+					cramfs_read(sb, blkptr_offset - 4, 4);
+			/* Beware... previous ptr might be a direct ptr */
+			if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
+				/* See comments on earlier code. */
+				u32 prev_start = block_start;
+				block_start = prev_start & ~CRAMFS_BLK_FLAGS;
+				block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
+				if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
+					block_start += PAGE_SIZE;
+				} else {
+					block_len = *(u16 *)
+						cramfs_read(sb, block_start, 2);
+					block_start += 2 + block_len;
+				}
+			}
+			block_start &= ~CRAMFS_BLK_FLAGS;
+			block_len = block_ptr - block_start;
+		}
+
+		if (block_len == 0)
+			; /* hole */
+		else if (unlikely(block_len > 2*PAGE_SIZE ||
+				  (uncompressed && block_len > PAGE_SIZE))) {
+			mutex_unlock(&read_mutex);
+			pr_err("bad data blocksize %u\n", block_len);
+			goto err;
+		} else if (uncompressed) {
+			memcpy(pgdata,
+			       cramfs_read(sb, block_start, block_len),
+			       block_len);
+			bytes_filled = block_len;
+		} else {
+			bytes_filled = cramfs_uncompress_block(pgdata,
+				 PAGE_SIZE,
+				 cramfs_read(sb, block_start, block_len),
+				 block_len);
+		}
+		mutex_unlock(&read_mutex);
+		if (unlikely(bytes_filled < 0))
+			goto err;
+	}
+
+	memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
+	flush_dcache_page(page);
+	kunmap_local(pgdata);
+	SetPageUptodate(page);
+	unlock_page(page);
+	return 0;
+
+err:
+	kunmap_local(pgdata);
+	ClearPageUptodate(page);
+	SetPageError(page);
+	unlock_page(page);
+	return 0;
+}
+
+static const struct address_space_operations cramfs_aops = {
+	.read_folio = cramfs_read_folio
+};
+
+/*
+ * Our operations:
+ */
+
+/*
+ * A directory can only readdir
+ */
+static const struct file_operations cramfs_directory_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= cramfs_readdir,
+};
+
+static const struct inode_operations cramfs_dir_inode_operations = {
+	.lookup		= cramfs_lookup,
+};
+
+static const struct super_operations cramfs_ops = {
+	.statfs		= cramfs_statfs,
+};
+
+static int cramfs_get_tree(struct fs_context *fc)
+{
+	int ret = -ENOPROTOOPT;
+
+	if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
+		ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
+		if (!ret)
+			return 0;
+	}
+	if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
+		ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
+	return ret;
+}
+
+static const struct fs_context_operations cramfs_context_ops = {
+	.get_tree	= cramfs_get_tree,
+	.reconfigure	= cramfs_reconfigure,
+};
+
+/*
+ * Set up the filesystem mount context.
+ */
+static int cramfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &cramfs_context_ops;
+	return 0;
+}
+
+static struct file_system_type cramfs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "cramfs",
+	.init_fs_context = cramfs_init_fs_context,
+	.kill_sb	= cramfs_kill_sb,
+	.fs_flags	= FS_REQUIRES_DEV,
+};
+MODULE_ALIAS_FS("cramfs");
+
+static int __init init_cramfs_fs(void)
+{
+	int rv;
+
+	rv = cramfs_uncompress_init();
+	if (rv < 0)
+		return rv;
+	rv = register_filesystem(&cramfs_fs_type);
+	if (rv < 0)
+		cramfs_uncompress_exit();
+	return rv;
+}
+
+static void __exit exit_cramfs_fs(void)
+{
+	cramfs_uncompress_exit();
+	unregister_filesystem(&cramfs_fs_type);
+}
+
+module_init(init_cramfs_fs)
+module_exit(exit_cramfs_fs)
+MODULE_LICENSE("GPL");
diff --git a/fs/cramfs/internal.h b/fs/cramfs/internal.h
new file mode 100644
index 0000000000..349d712721
--- /dev/null
+++ b/fs/cramfs/internal.h
@@ -0,0 +1,4 @@
+/* Uncompression interfaces to the underlying zlib */
+int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen);
+int cramfs_uncompress_init(void);
+void cramfs_uncompress_exit(void);
diff --git a/fs/cramfs/uncompress.c b/fs/cramfs/uncompress.c
new file mode 100644
index 0000000000..975d98fc26
--- /dev/null
+++ b/fs/cramfs/uncompress.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * uncompress.c
+ *
+ * (C) Copyright 1999 Linus Torvalds
+ *
+ * cramfs interfaces to the uncompression library. There's really just
+ * three entrypoints:
+ *
+ *  - cramfs_uncompress_init() - called to initialize the thing.
+ *  - cramfs_uncompress_exit() - tell me when you're done
+ *  - cramfs_uncompress_block() - uncompress a block.
+ *
+ * NOTE NOTE NOTE! The uncompression is entirely single-threaded. We
+ * only have one stream, and we'll initialize it only once even if it
+ * then is used by multiple filesystems.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/vmalloc.h>
+#include <linux/zlib.h>
+#include "internal.h"
+
+static z_stream stream;
+static int initialized;
+
+/* Returns length of decompressed data. */
+int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen)
+{
+	int err;
+
+	stream.next_in = src;
+	stream.avail_in = srclen;
+
+	stream.next_out = dst;
+	stream.avail_out = dstlen;
+
+	err = zlib_inflateReset(&stream);
+	if (err != Z_OK) {
+		pr_err("zlib_inflateReset error %d\n", err);
+		zlib_inflateEnd(&stream);
+		zlib_inflateInit(&stream);
+	}
+
+	err = zlib_inflate(&stream, Z_FINISH);
+	if (err != Z_STREAM_END)
+		goto err;
+	return stream.total_out;
+
+err:
+	pr_err("Error %d while decompressing!\n", err);
+	pr_err("%p(%d)->%p(%d)\n", src, srclen, dst, dstlen);
+	return -EIO;
+}
+
+int cramfs_uncompress_init(void)
+{
+	if (!initialized++) {
+		stream.workspace = vmalloc(zlib_inflate_workspacesize());
+		if (!stream.workspace) {
+			initialized = 0;
+			return -ENOMEM;
+		}
+		stream.next_in = NULL;
+		stream.avail_in = 0;
+		zlib_inflateInit(&stream);
+	}
+	return 0;
+}
+
+void cramfs_uncompress_exit(void)
+{
+	if (!--initialized) {
+		zlib_inflateEnd(&stream);
+		vfree(stream.workspace);
+	}
+}