Adding upstream version 4.19.249.upstream/4.19.249

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

1 files changed, 1034 insertions, 0 deletions

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
new file mode 100644
index 000000000..bd1d68ff3
--- /dev/null
+++ b/fs/ext2/xattr.c
@@ -0,0 +1,1034 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext2/xattr.c
+ *
+ * Copyright (C) 2001-2003 Andreas Gruenbacher <agruen@suse.de>
+ *
+ * Fix by Harrison Xing <harrison@mountainviewdata.com>.
+ * Extended attributes for symlinks and special files added per
+ *  suggestion of Luka Renko <luka.renko@hermes.si>.
+ * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
+ *  Red Hat Inc.
+ *
+ */
+
+/*
+ * Extended attributes are stored on disk blocks allocated outside of
+ * any inode. The i_file_acl field is then made to point to this allocated
+ * block. If all extended attributes of an inode are identical, these
+ * inodes may share the same extended attribute block. Such situations
+ * are automatically detected by keeping a cache of recent attribute block
+ * numbers and hashes over the block's contents in memory.
+ *
+ *
+ * Extended attribute block layout:
+ *
+ *   +------------------+
+ *   | header           |
+ *   | entry 1          | |
+ *   | entry 2          | | growing downwards
+ *   | entry 3          | v
+ *   | four null bytes  |
+ *   | . . .            |
+ *   | value 1          | ^
+ *   | value 3          | | growing upwards
+ *   | value 2          | |
+ *   +------------------+
+ *
+ * The block header is followed by multiple entry descriptors. These entry
+ * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
+ * byte boundaries. The entry descriptors are sorted by attribute name,
+ * so that two extended attribute blocks can be compared efficiently.
+ *
+ * Attribute values are aligned to the end of the block, stored in
+ * no specific order. They are also padded to EXT2_XATTR_PAD byte
+ * boundaries. No additional gaps are left between them.
+ *
+ * Locking strategy
+ * ----------------
+ * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
+ * EA blocks are only changed if they are exclusive to an inode, so
+ * holding xattr_sem also means that nothing but the EA block's reference
+ * count will change. Multiple writers to an EA block are synchronized
+ * by the bh lock. No more than a single bh lock is held at any time
+ * to avoid deadlocks.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/init.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/mbcache.h>
+#include <linux/quotaops.h>
+#include <linux/rwsem.h>
+#include <linux/security.h>
+#include "ext2.h"
+#include "xattr.h"
+#include "acl.h"
+
+#define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
+#define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
+#define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
+#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
+
+#ifdef EXT2_XATTR_DEBUG
+# define ea_idebug(inode, f...) do { \
+		printk(KERN_DEBUG "inode %s:%ld: ", \
+			inode->i_sb->s_id, inode->i_ino); \
+		printk(f); \
+		printk("\n"); \
+	} while (0)
+# define ea_bdebug(bh, f...) do { \
+		printk(KERN_DEBUG "block %pg:%lu: ", \
+			bh->b_bdev, (unsigned long) bh->b_blocknr); \
+		printk(f); \
+		printk("\n"); \
+	} while (0)
+#else
+# define ea_idebug(inode, f...)	no_printk(f)
+# define ea_bdebug(bh, f...)	no_printk(f)
+#endif
+
+static int ext2_xattr_set2(struct inode *, struct buffer_head *,
+			   struct ext2_xattr_header *);
+
+static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
+static struct buffer_head *ext2_xattr_cache_find(struct inode *,
+						 struct ext2_xattr_header *);
+static void ext2_xattr_rehash(struct ext2_xattr_header *,
+			      struct ext2_xattr_entry *);
+
+static const struct xattr_handler *ext2_xattr_handler_map[] = {
+	[EXT2_XATTR_INDEX_USER]		     = &ext2_xattr_user_handler,
+#ifdef CONFIG_EXT2_FS_POSIX_ACL
+	[EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
+	[EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
+#endif
+	[EXT2_XATTR_INDEX_TRUSTED]	     = &ext2_xattr_trusted_handler,
+#ifdef CONFIG_EXT2_FS_SECURITY
+	[EXT2_XATTR_INDEX_SECURITY]	     = &ext2_xattr_security_handler,
+#endif
+};
+
+const struct xattr_handler *ext2_xattr_handlers[] = {
+	&ext2_xattr_user_handler,
+	&ext2_xattr_trusted_handler,
+#ifdef CONFIG_EXT2_FS_POSIX_ACL
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
+#endif
+#ifdef CONFIG_EXT2_FS_SECURITY
+	&ext2_xattr_security_handler,
+#endif
+	NULL
+};
+
+#define EA_BLOCK_CACHE(inode)	(EXT2_SB(inode->i_sb)->s_ea_block_cache)
+
+static inline const struct xattr_handler *
+ext2_xattr_handler(int name_index)
+{
+	const struct xattr_handler *handler = NULL;
+
+	if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
+		handler = ext2_xattr_handler_map[name_index];
+	return handler;
+}
+
+/*
+ * ext2_xattr_get()
+ *
+ * Copy an extended attribute into the buffer
+ * provided, or compute the buffer size required.
+ * Buffer is NULL to compute the size of the buffer required.
+ *
+ * Returns a negative error number on failure, or the number of bytes
+ * used / required on success.
+ */
+int
+ext2_xattr_get(struct inode *inode, int name_index, const char *name,
+	       void *buffer, size_t buffer_size)
+{
+	struct buffer_head *bh = NULL;
+	struct ext2_xattr_entry *entry;
+	size_t name_len, size;
+	char *end;
+	int error;
+	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
+
+	ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
+		  name_index, name, buffer, (long)buffer_size);
+
+	if (name == NULL)
+		return -EINVAL;
+	name_len = strlen(name);
+	if (name_len > 255)
+		return -ERANGE;
+
+	down_read(&EXT2_I(inode)->xattr_sem);
+	error = -ENODATA;
+	if (!EXT2_I(inode)->i_file_acl)
+		goto cleanup;
+	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
+	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
+	error = -EIO;
+	if (!bh)
+		goto cleanup;
+	ea_bdebug(bh, "b_count=%d, refcount=%d",
+		atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
+	end = bh->b_data + bh->b_size;
+	if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
+	    HDR(bh)->h_blocks != cpu_to_le32(1)) {
+bad_block:	ext2_error(inode->i_sb, "ext2_xattr_get",
+			"inode %ld: bad block %d", inode->i_ino,
+			EXT2_I(inode)->i_file_acl);
+		error = -EIO;
+		goto cleanup;
+	}
+
+	/* find named attribute */
+	entry = FIRST_ENTRY(bh);
+	while (!IS_LAST_ENTRY(entry)) {
+		struct ext2_xattr_entry *next =
+			EXT2_XATTR_NEXT(entry);
+		if ((char *)next >= end)
+			goto bad_block;
+		if (name_index == entry->e_name_index &&
+		    name_len == entry->e_name_len &&
+		    memcmp(name, entry->e_name, name_len) == 0)
+			goto found;
+		entry = next;
+	}
+	if (ext2_xattr_cache_insert(ea_block_cache, bh))
+		ea_idebug(inode, "cache insert failed");
+	error = -ENODATA;
+	goto cleanup;
+found:
+	/* check the buffer size */
+	if (entry->e_value_block != 0)
+		goto bad_block;
+	size = le32_to_cpu(entry->e_value_size);
+	if (size > inode->i_sb->s_blocksize ||
+	    le16_to_cpu(entry->e_value_offs) + size > inode->i_sb->s_blocksize)
+		goto bad_block;
+
+	if (ext2_xattr_cache_insert(ea_block_cache, bh))
+		ea_idebug(inode, "cache insert failed");
+	if (buffer) {
+		error = -ERANGE;
+		if (size > buffer_size)
+			goto cleanup;
+		/* return value of attribute */
+		memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
+			size);
+	}
+	error = size;
+
+cleanup:
+	brelse(bh);
+	up_read(&EXT2_I(inode)->xattr_sem);
+
+	return error;
+}
+
+/*
+ * ext2_xattr_list()
+ *
+ * Copy a list of attribute names into the buffer
+ * provided, or compute the buffer size required.
+ * Buffer is NULL to compute the size of the buffer required.
+ *
+ * Returns a negative error number on failure, or the number of bytes
+ * used / required on success.
+ */
+static int
+ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
+{
+	struct inode *inode = d_inode(dentry);
+	struct buffer_head *bh = NULL;
+	struct ext2_xattr_entry *entry;
+	char *end;
+	size_t rest = buffer_size;
+	int error;
+	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
+
+	ea_idebug(inode, "buffer=%p, buffer_size=%ld",
+		  buffer, (long)buffer_size);
+
+	down_read(&EXT2_I(inode)->xattr_sem);
+	error = 0;
+	if (!EXT2_I(inode)->i_file_acl)
+		goto cleanup;
+	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
+	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
+	error = -EIO;
+	if (!bh)
+		goto cleanup;
+	ea_bdebug(bh, "b_count=%d, refcount=%d",
+		atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
+	end = bh->b_data + bh->b_size;
+	if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
+	    HDR(bh)->h_blocks != cpu_to_le32(1)) {
+bad_block:	ext2_error(inode->i_sb, "ext2_xattr_list",
+			"inode %ld: bad block %d", inode->i_ino,
+			EXT2_I(inode)->i_file_acl);
+		error = -EIO;
+		goto cleanup;
+	}
+
+	/* check the on-disk data structure */
+	entry = FIRST_ENTRY(bh);
+	while (!IS_LAST_ENTRY(entry)) {
+		struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(entry);
+
+		if ((char *)next >= end)
+			goto bad_block;
+		entry = next;
+	}
+	if (ext2_xattr_cache_insert(ea_block_cache, bh))
+		ea_idebug(inode, "cache insert failed");
+
+	/* list the attribute names */
+	for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
+	     entry = EXT2_XATTR_NEXT(entry)) {
+		const struct xattr_handler *handler =
+			ext2_xattr_handler(entry->e_name_index);
+
+		if (handler && (!handler->list || handler->list(dentry))) {
+			const char *prefix = handler->prefix ?: handler->name;
+			size_t prefix_len = strlen(prefix);
+			size_t size = prefix_len + entry->e_name_len + 1;
+
+			if (buffer) {
+				if (size > rest) {
+					error = -ERANGE;
+					goto cleanup;
+				}
+				memcpy(buffer, prefix, prefix_len);
+				buffer += prefix_len;
+				memcpy(buffer, entry->e_name, entry->e_name_len);
+				buffer += entry->e_name_len;
+				*buffer++ = 0;
+			}
+			rest -= size;
+		}
+	}
+	error = buffer_size - rest;  /* total size */
+
+cleanup:
+	brelse(bh);
+	up_read(&EXT2_I(inode)->xattr_sem);
+
+	return error;
+}
+
+/*
+ * Inode operation listxattr()
+ *
+ * d_inode(dentry)->i_mutex: don't care
+ */
+ssize_t
+ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+	return ext2_xattr_list(dentry, buffer, size);
+}
+
+/*
+ * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
+ * not set, set it.
+ */
+static void ext2_xattr_update_super_block(struct super_block *sb)
+{
+	if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
+		return;
+
+	spin_lock(&EXT2_SB(sb)->s_lock);
+	EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
+	spin_unlock(&EXT2_SB(sb)->s_lock);
+	mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
+}
+
+/*
+ * ext2_xattr_set()
+ *
+ * Create, replace or remove an extended attribute for this inode.  Value
+ * is NULL to remove an existing extended attribute, and non-NULL to
+ * either replace an existing extended attribute, or create a new extended
+ * attribute. The flags XATTR_REPLACE and XATTR_CREATE
+ * specify that an extended attribute must exist and must not exist
+ * previous to the call, respectively.
+ *
+ * Returns 0, or a negative error number on failure.
+ */
+int
+ext2_xattr_set(struct inode *inode, int name_index, const char *name,
+	       const void *value, size_t value_len, int flags)
+{
+	struct super_block *sb = inode->i_sb;
+	struct buffer_head *bh = NULL;
+	struct ext2_xattr_header *header = NULL;
+	struct ext2_xattr_entry *here, *last;
+	size_t name_len, free, min_offs = sb->s_blocksize;
+	int not_found = 1, error;
+	char *end;
+	
+	/*
+	 * header -- Points either into bh, or to a temporarily
+	 *           allocated buffer.
+	 * here -- The named entry found, or the place for inserting, within
+	 *         the block pointed to by header.
+	 * last -- Points right after the last named entry within the block
+	 *         pointed to by header.
+	 * min_offs -- The offset of the first value (values are aligned
+	 *             towards the end of the block).
+	 * end -- Points right after the block pointed to by header.
+	 */
+	
+	ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
+		  name_index, name, value, (long)value_len);
+
+	if (value == NULL)
+		value_len = 0;
+	if (name == NULL)
+		return -EINVAL;
+	name_len = strlen(name);
+	if (name_len > 255 || value_len > sb->s_blocksize)
+		return -ERANGE;
+	down_write(&EXT2_I(inode)->xattr_sem);
+	if (EXT2_I(inode)->i_file_acl) {
+		/* The inode already has an extended attribute block. */
+		bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
+		error = -EIO;
+		if (!bh)
+			goto cleanup;
+		ea_bdebug(bh, "b_count=%d, refcount=%d",
+			atomic_read(&(bh->b_count)),
+			le32_to_cpu(HDR(bh)->h_refcount));
+		header = HDR(bh);
+		end = bh->b_data + bh->b_size;
+		if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
+		    header->h_blocks != cpu_to_le32(1)) {
+bad_block:		ext2_error(sb, "ext2_xattr_set",
+				"inode %ld: bad block %d", inode->i_ino, 
+				   EXT2_I(inode)->i_file_acl);
+			error = -EIO;
+			goto cleanup;
+		}
+		/* Find the named attribute. */
+		here = FIRST_ENTRY(bh);
+		while (!IS_LAST_ENTRY(here)) {
+			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(here);
+			if ((char *)next >= end)
+				goto bad_block;
+			if (!here->e_value_block && here->e_value_size) {
+				size_t offs = le16_to_cpu(here->e_value_offs);
+				if (offs < min_offs)
+					min_offs = offs;
+			}
+			not_found = name_index - here->e_name_index;
+			if (!not_found)
+				not_found = name_len - here->e_name_len;
+			if (!not_found)
+				not_found = memcmp(name, here->e_name,name_len);
+			if (not_found <= 0)
+				break;
+			here = next;
+		}
+		last = here;
+		/* We still need to compute min_offs and last. */
+		while (!IS_LAST_ENTRY(last)) {
+			struct ext2_xattr_entry *next = EXT2_XATTR_NEXT(last);
+			if ((char *)next >= end)
+				goto bad_block;
+			if (!last->e_value_block && last->e_value_size) {
+				size_t offs = le16_to_cpu(last->e_value_offs);
+				if (offs < min_offs)
+					min_offs = offs;
+			}
+			last = next;
+		}
+
+		/* Check whether we have enough space left. */
+		free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
+	} else {
+		/* We will use a new extended attribute block. */
+		free = sb->s_blocksize -
+			sizeof(struct ext2_xattr_header) - sizeof(__u32);
+		here = last = NULL;  /* avoid gcc uninitialized warning. */
+	}
+
+	if (not_found) {
+		/* Request to remove a nonexistent attribute? */
+		error = -ENODATA;
+		if (flags & XATTR_REPLACE)
+			goto cleanup;
+		error = 0;
+		if (value == NULL)
+			goto cleanup;
+	} else {
+		/* Request to create an existing attribute? */
+		error = -EEXIST;
+		if (flags & XATTR_CREATE)
+			goto cleanup;
+		if (!here->e_value_block && here->e_value_size) {
+			size_t size = le32_to_cpu(here->e_value_size);
+
+			if (le16_to_cpu(here->e_value_offs) + size > 
+			    sb->s_blocksize || size > sb->s_blocksize)
+				goto bad_block;
+			free += EXT2_XATTR_SIZE(size);
+		}
+		free += EXT2_XATTR_LEN(name_len);
+	}
+	error = -ENOSPC;
+	if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
+		goto cleanup;
+
+	/* Here we know that we can set the new attribute. */
+
+	if (header) {
+		/* assert(header == HDR(bh)); */
+		lock_buffer(bh);
+		if (header->h_refcount == cpu_to_le32(1)) {
+			__u32 hash = le32_to_cpu(header->h_hash);
+
+			ea_bdebug(bh, "modifying in-place");
+			/*
+			 * This must happen under buffer lock for
+			 * ext2_xattr_set2() to reliably detect modified block
+			 */
+			mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
+					      bh->b_blocknr);
+
+			/* keep the buffer locked while modifying it. */
+		} else {
+			int offset;
+
+			unlock_buffer(bh);
+			ea_bdebug(bh, "cloning");
+			header = kmalloc(bh->b_size, GFP_KERNEL);
+			error = -ENOMEM;
+			if (header == NULL)
+				goto cleanup;
+			memcpy(header, HDR(bh), bh->b_size);
+			header->h_refcount = cpu_to_le32(1);
+
+			offset = (char *)here - bh->b_data;
+			here = ENTRY((char *)header + offset);
+			offset = (char *)last - bh->b_data;
+			last = ENTRY((char *)header + offset);
+		}
+	} else {
+		/* Allocate a buffer where we construct the new block. */
+		header = kzalloc(sb->s_blocksize, GFP_KERNEL);
+		error = -ENOMEM;
+		if (header == NULL)
+			goto cleanup;
+		end = (char *)header + sb->s_blocksize;
+		header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
+		header->h_blocks = header->h_refcount = cpu_to_le32(1);
+		last = here = ENTRY(header+1);
+	}
+
+	/* Iff we are modifying the block in-place, bh is locked here. */
+
+	if (not_found) {
+		/* Insert the new name. */
+		size_t size = EXT2_XATTR_LEN(name_len);
+		size_t rest = (char *)last - (char *)here;
+		memmove((char *)here + size, here, rest);
+		memset(here, 0, size);
+		here->e_name_index = name_index;
+		here->e_name_len = name_len;
+		memcpy(here->e_name, name, name_len);
+	} else {
+		if (!here->e_value_block && here->e_value_size) {
+			char *first_val = (char *)header + min_offs;
+			size_t offs = le16_to_cpu(here->e_value_offs);
+			char *val = (char *)header + offs;
+			size_t size = EXT2_XATTR_SIZE(
+				le32_to_cpu(here->e_value_size));
+
+			if (size == EXT2_XATTR_SIZE(value_len)) {
+				/* The old and the new value have the same
+				   size. Just replace. */
+				here->e_value_size = cpu_to_le32(value_len);
+				memset(val + size - EXT2_XATTR_PAD, 0,
+				       EXT2_XATTR_PAD); /* Clear pad bytes. */
+				memcpy(val, value, value_len);
+				goto skip_replace;
+			}
+
+			/* Remove the old value. */
+			memmove(first_val + size, first_val, val - first_val);
+			memset(first_val, 0, size);
+			here->e_value_offs = 0;
+			min_offs += size;
+
+			/* Adjust all value offsets. */
+			last = ENTRY(header+1);
+			while (!IS_LAST_ENTRY(last)) {
+				size_t o = le16_to_cpu(last->e_value_offs);
+				if (!last->e_value_block && o < offs)
+					last->e_value_offs =
+						cpu_to_le16(o + size);
+				last = EXT2_XATTR_NEXT(last);
+			}
+		}
+		if (value == NULL) {
+			/* Remove the old name. */
+			size_t size = EXT2_XATTR_LEN(name_len);
+			last = ENTRY((char *)last - size);
+			memmove(here, (char*)here + size,
+				(char*)last - (char*)here);
+			memset(last, 0, size);
+		}
+	}
+
+	if (value != NULL) {
+		/* Insert the new value. */
+		here->e_value_size = cpu_to_le32(value_len);
+		if (value_len) {
+			size_t size = EXT2_XATTR_SIZE(value_len);
+			char *val = (char *)header + min_offs - size;
+			here->e_value_offs =
+				cpu_to_le16((char *)val - (char *)header);
+			memset(val + size - EXT2_XATTR_PAD, 0,
+			       EXT2_XATTR_PAD); /* Clear the pad bytes. */
+			memcpy(val, value, value_len);
+		}
+	}
+
+skip_replace:
+	if (IS_LAST_ENTRY(ENTRY(header+1))) {
+		/* This block is now empty. */
+		if (bh && header == HDR(bh))
+			unlock_buffer(bh);  /* we were modifying in-place. */
+		error = ext2_xattr_set2(inode, bh, NULL);
+	} else {
+		ext2_xattr_rehash(header, here);
+		if (bh && header == HDR(bh))
+			unlock_buffer(bh);  /* we were modifying in-place. */
+		error = ext2_xattr_set2(inode, bh, header);
+	}
+
+cleanup:
+	if (!(bh && header == HDR(bh)))
+		kfree(header);
+	brelse(bh);
+	up_write(&EXT2_I(inode)->xattr_sem);
+
+	return error;
+}
+
+/*
+ * Second half of ext2_xattr_set(): Update the file system.
+ */
+static int
+ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
+		struct ext2_xattr_header *header)
+{
+	struct super_block *sb = inode->i_sb;
+	struct buffer_head *new_bh = NULL;
+	int error;
+	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
+
+	if (header) {
+		new_bh = ext2_xattr_cache_find(inode, header);
+		if (new_bh) {
+			/* We found an identical block in the cache. */
+			if (new_bh == old_bh) {
+				ea_bdebug(new_bh, "keeping this block");
+			} else {
+				/* The old block is released after updating
+				   the inode.  */
+				ea_bdebug(new_bh, "reusing block");
+
+				error = dquot_alloc_block(inode, 1);
+				if (error) {
+					unlock_buffer(new_bh);
+					goto cleanup;
+				}
+				le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
+				ea_bdebug(new_bh, "refcount now=%d",
+					le32_to_cpu(HDR(new_bh)->h_refcount));
+			}
+			unlock_buffer(new_bh);
+		} else if (old_bh && header == HDR(old_bh)) {
+			/* Keep this block. No need to lock the block as we
+			   don't need to change the reference count. */
+			new_bh = old_bh;
+			get_bh(new_bh);
+			ext2_xattr_cache_insert(ea_block_cache, new_bh);
+		} else {
+			/* We need to allocate a new block */
+			ext2_fsblk_t goal = ext2_group_first_block_no(sb,
+						EXT2_I(inode)->i_block_group);
+			int block = ext2_new_block(inode, goal, &error);
+			if (error)
+				goto cleanup;
+			ea_idebug(inode, "creating block %d", block);
+
+			new_bh = sb_getblk(sb, block);
+			if (unlikely(!new_bh)) {
+				ext2_free_blocks(inode, block, 1);
+				mark_inode_dirty(inode);
+				error = -ENOMEM;
+				goto cleanup;
+			}
+			lock_buffer(new_bh);
+			memcpy(new_bh->b_data, header, new_bh->b_size);
+			set_buffer_uptodate(new_bh);
+			unlock_buffer(new_bh);
+			ext2_xattr_cache_insert(ea_block_cache, new_bh);
+			
+			ext2_xattr_update_super_block(sb);
+		}
+		mark_buffer_dirty(new_bh);
+		if (IS_SYNC(inode)) {
+			sync_dirty_buffer(new_bh);
+			error = -EIO;
+			if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
+				goto cleanup;
+		}
+	}
+
+	/* Update the inode. */
+	EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
+	inode->i_ctime = current_time(inode);
+	if (IS_SYNC(inode)) {
+		error = sync_inode_metadata(inode, 1);
+		/* In case sync failed due to ENOSPC the inode was actually
+		 * written (only some dirty data were not) so we just proceed
+		 * as if nothing happened and cleanup the unused block */
+		if (error && error != -ENOSPC) {
+			if (new_bh && new_bh != old_bh) {
+				dquot_free_block_nodirty(inode, 1);
+				mark_inode_dirty(inode);
+			}
+			goto cleanup;
+		}
+	} else
+		mark_inode_dirty(inode);
+
+	error = 0;
+	if (old_bh && old_bh != new_bh) {
+		/*
+		 * If there was an old block and we are no longer using it,
+		 * release the old block.
+		 */
+		lock_buffer(old_bh);
+		if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
+			__u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
+
+			/*
+			 * This must happen under buffer lock for
+			 * ext2_xattr_set2() to reliably detect freed block
+			 */
+			mb_cache_entry_delete(ea_block_cache, hash,
+					      old_bh->b_blocknr);
+			/* Free the old block. */
+			ea_bdebug(old_bh, "freeing");
+			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
+			mark_inode_dirty(inode);
+			/* We let our caller release old_bh, so we
+			 * need to duplicate the buffer before. */
+			get_bh(old_bh);
+			bforget(old_bh);
+		} else {
+			/* Decrement the refcount only. */
+			le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
+			dquot_free_block_nodirty(inode, 1);
+			mark_inode_dirty(inode);
+			mark_buffer_dirty(old_bh);
+			ea_bdebug(old_bh, "refcount now=%d",
+				le32_to_cpu(HDR(old_bh)->h_refcount));
+		}
+		unlock_buffer(old_bh);
+	}
+
+cleanup:
+	brelse(new_bh);
+
+	return error;
+}
+
+/*
+ * ext2_xattr_delete_inode()
+ *
+ * Free extended attribute resources associated with this inode. This
+ * is called immediately before an inode is freed.
+ */
+void
+ext2_xattr_delete_inode(struct inode *inode)
+{
+	struct buffer_head *bh = NULL;
+	struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
+
+	down_write(&EXT2_I(inode)->xattr_sem);
+	if (!EXT2_I(inode)->i_file_acl)
+		goto cleanup;
+
+	if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 0)) {
+		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
+			"inode %ld: xattr block %d is out of data blocks range",
+			inode->i_ino, EXT2_I(inode)->i_file_acl);
+		goto cleanup;
+	}
+
+	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
+	if (!bh) {
+		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
+			"inode %ld: block %d read error", inode->i_ino,
+			EXT2_I(inode)->i_file_acl);
+		goto cleanup;
+	}
+	ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
+	if (HDR(bh)->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
+	    HDR(bh)->h_blocks != cpu_to_le32(1)) {
+		ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
+			"inode %ld: bad block %d", inode->i_ino,
+			EXT2_I(inode)->i_file_acl);
+		goto cleanup;
+	}
+	lock_buffer(bh);
+	if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
+		__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
+
+		/*
+		 * This must happen under buffer lock for ext2_xattr_set2() to
+		 * reliably detect freed block
+		 */
+		mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
+				      bh->b_blocknr);
+		ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
+		get_bh(bh);
+		bforget(bh);
+		unlock_buffer(bh);
+	} else {
+		le32_add_cpu(&HDR(bh)->h_refcount, -1);
+		ea_bdebug(bh, "refcount now=%d",
+			le32_to_cpu(HDR(bh)->h_refcount));
+		unlock_buffer(bh);
+		mark_buffer_dirty(bh);
+		if (IS_SYNC(inode))
+			sync_dirty_buffer(bh);
+		dquot_free_block_nodirty(inode, 1);
+	}
+	EXT2_I(inode)->i_file_acl = 0;
+
+cleanup:
+	brelse(bh);
+	up_write(&EXT2_I(inode)->xattr_sem);
+}
+
+/*
+ * ext2_xattr_cache_insert()
+ *
+ * Create a new entry in the extended attribute cache, and insert
+ * it unless such an entry is already in the cache.
+ *
+ * Returns 0, or a negative error number on failure.
+ */
+static int
+ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
+{
+	__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
+	int error;
+
+	error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr, 1);
+	if (error) {
+		if (error == -EBUSY) {
+			ea_bdebug(bh, "already in cache");
+			error = 0;
+		}
+	} else
+		ea_bdebug(bh, "inserting [%x]", (int)hash);
+	return error;
+}
+
+/*
+ * ext2_xattr_cmp()
+ *
+ * Compare two extended attribute blocks for equality.
+ *
+ * Returns 0 if the blocks are equal, 1 if they differ, and
+ * a negative error number on errors.
+ */
+static int
+ext2_xattr_cmp(struct ext2_xattr_header *header1,
+	       struct ext2_xattr_header *header2)
+{
+	struct ext2_xattr_entry *entry1, *entry2;
+
+	entry1 = ENTRY(header1+1);
+	entry2 = ENTRY(header2+1);
+	while (!IS_LAST_ENTRY(entry1)) {
+		if (IS_LAST_ENTRY(entry2))
+			return 1;
+		if (entry1->e_hash != entry2->e_hash ||
+		    entry1->e_name_index != entry2->e_name_index ||
+		    entry1->e_name_len != entry2->e_name_len ||
+		    entry1->e_value_size != entry2->e_value_size ||
+		    memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
+			return 1;
+		if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
+			return -EIO;
+		if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
+			   (char *)header2 + le16_to_cpu(entry2->e_value_offs),
+			   le32_to_cpu(entry1->e_value_size)))
+			return 1;
+
+		entry1 = EXT2_XATTR_NEXT(entry1);
+		entry2 = EXT2_XATTR_NEXT(entry2);
+	}
+	if (!IS_LAST_ENTRY(entry2))
+		return 1;
+	return 0;
+}
+
+/*
+ * ext2_xattr_cache_find()
+ *
+ * Find an identical extended attribute block.
+ *
+ * Returns a locked buffer head to the block found, or NULL if such
+ * a block was not found or an error occurred.
+ */
+static struct buffer_head *
+ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
+{
+	__u32 hash = le32_to_cpu(header->h_hash);
+	struct mb_cache_entry *ce;
+	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
+
+	if (!header->h_hash)
+		return NULL;  /* never share */
+	ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
+again:
+	ce = mb_cache_entry_find_first(ea_block_cache, hash);
+	while (ce) {
+		struct buffer_head *bh;
+
+		bh = sb_bread(inode->i_sb, ce->e_value);
+		if (!bh) {
+			ext2_error(inode->i_sb, "ext2_xattr_cache_find",
+				"inode %ld: block %ld read error",
+				inode->i_ino, (unsigned long) ce->e_value);
+		} else {
+			lock_buffer(bh);
+			/*
+			 * We have to be careful about races with freeing or
+			 * rehashing of xattr block. Once we hold buffer lock
+			 * xattr block's state is stable so we can check
+			 * whether the block got freed / rehashed or not.
+			 * Since we unhash mbcache entry under buffer lock when
+			 * freeing / rehashing xattr block, checking whether
+			 * entry is still hashed is reliable.
+			 */
+			if (hlist_bl_unhashed(&ce->e_hash_list)) {
+				mb_cache_entry_put(ea_block_cache, ce);
+				unlock_buffer(bh);
+				brelse(bh);
+				goto again;
+			} else if (le32_to_cpu(HDR(bh)->h_refcount) >
+				   EXT2_XATTR_REFCOUNT_MAX) {
+				ea_idebug(inode, "block %ld refcount %d>%d",
+					  (unsigned long) ce->e_value,
+					  le32_to_cpu(HDR(bh)->h_refcount),
+					  EXT2_XATTR_REFCOUNT_MAX);
+			} else if (!ext2_xattr_cmp(header, HDR(bh))) {
+				ea_bdebug(bh, "b_count=%d",
+					  atomic_read(&(bh->b_count)));
+				mb_cache_entry_touch(ea_block_cache, ce);
+				mb_cache_entry_put(ea_block_cache, ce);
+				return bh;
+			}
+			unlock_buffer(bh);
+			brelse(bh);
+		}
+		ce = mb_cache_entry_find_next(ea_block_cache, ce);
+	}
+	return NULL;
+}
+
+#define NAME_HASH_SHIFT 5
+#define VALUE_HASH_SHIFT 16
+
+/*
+ * ext2_xattr_hash_entry()
+ *
+ * Compute the hash of an extended attribute.
+ */
+static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
+					 struct ext2_xattr_entry *entry)
+{
+	__u32 hash = 0;
+	char *name = entry->e_name;
+	int n;
+
+	for (n=0; n < entry->e_name_len; n++) {
+		hash = (hash << NAME_HASH_SHIFT) ^
+		       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
+		       *name++;
+	}
+
+	if (entry->e_value_block == 0 && entry->e_value_size != 0) {
+		__le32 *value = (__le32 *)((char *)header +
+			le16_to_cpu(entry->e_value_offs));
+		for (n = (le32_to_cpu(entry->e_value_size) +
+		     EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
+			hash = (hash << VALUE_HASH_SHIFT) ^
+			       (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
+			       le32_to_cpu(*value++);
+		}
+	}
+	entry->e_hash = cpu_to_le32(hash);
+}
+
+#undef NAME_HASH_SHIFT
+#undef VALUE_HASH_SHIFT
+
+#define BLOCK_HASH_SHIFT 16
+
+/*
+ * ext2_xattr_rehash()
+ *
+ * Re-compute the extended attribute hash value after an entry has changed.
+ */
+static void ext2_xattr_rehash(struct ext2_xattr_header *header,
+			      struct ext2_xattr_entry *entry)
+{
+	struct ext2_xattr_entry *here;
+	__u32 hash = 0;
+	
+	ext2_xattr_hash_entry(header, entry);
+	here = ENTRY(header+1);
+	while (!IS_LAST_ENTRY(here)) {
+		if (!here->e_hash) {
+			/* Block is not shared if an entry's hash value == 0 */
+			hash = 0;
+			break;
+		}
+		hash = (hash << BLOCK_HASH_SHIFT) ^
+		       (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
+		       le32_to_cpu(here->e_hash);
+		here = EXT2_XATTR_NEXT(here);
+	}
+	header->h_hash = cpu_to_le32(hash);
+}
+
+#undef BLOCK_HASH_SHIFT
+
+#define HASH_BUCKET_BITS 10
+
+struct mb_cache *ext2_xattr_create_cache(void)
+{
+	return mb_cache_create(HASH_BUCKET_BITS);
+}
+
+void ext2_xattr_destroy_cache(struct mb_cache *cache)
+{
+	if (cache)
+		mb_cache_destroy(cache);
+}