Port of (bugfixed) 0.8.50 xattr-ext2 to 2.5 (w/ hch cleanups. mbcache API)

This patch adds extended attribute support to the ext2 filesystem.  This
uses the generic extended attribute patch which was developed by Andreas
Gruenbacher and the XFS team.  As a result, the user space utilities
which work for XFS will also work with these patches.

1 files changed, 1118 insertions, 0 deletions

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
new file mode 100644
index 00000000000000..2f937032c80c26
--- /dev/null
+++ b/fs/ext2/xattr.c
@@ -0,0 +1,1118 @@
+/*
+ * linux/fs/ext2/xattr.c
+ *
+ * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
+ *
+ * Fix by Harrison Xing <harrison@mountainviewdata.com>.
+ * Extended attributes for symlinks and special files added per
+ *  suggestion of Luka Renko <luka.renko@hermes.si>.
+ */
+
+/*
+ * 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 alligned 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
+ * ----------------
+ * The VFS already holds the BKL and the inode->i_sem semaphore when any of
+ * the xattr inode operations are called, so we are guaranteed that only one
+ * processes accesses extended attributes of an inode at any time.
+ *
+ * For writing we also grab the ext2_xattr_sem semaphore. This ensures that
+ * only a single process is modifying an extended attribute block, even
+ * if the block is shared among inodes.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/mbcache.h>
+#include <linux/quotaops.h>
+#include <asm/semaphore.h>
+#include "ext2.h"
+#include "xattr.h"
+
+/* These symbols may be needed by a module. */
+EXPORT_SYMBOL(ext2_xattr_register);
+EXPORT_SYMBOL(ext2_xattr_unregister);
+EXPORT_SYMBOL(ext2_xattr_get);
+EXPORT_SYMBOL(ext2_xattr_list);
+EXPORT_SYMBOL(ext2_xattr_set);
+
+#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: ", \
+			kdevname(inode->i_dev), inode->i_ino); \
+		printk(f); \
+		printk("\n"); \
+	} while (0)
+# define ea_bdebug(bh, f...) do { \
+		printk(KERN_DEBUG "block %s:%ld: ", \
+			kdevname(bh->b_dev), bh->b_blocknr); \
+		printk(f); \
+		printk("\n"); \
+	} while (0)
+#else
+# define ea_idebug(f...)
+# define ea_bdebug(f...)
+#endif
+
+static int ext2_xattr_set2(struct inode *, struct buffer_head *,
+			   struct ext2_xattr_header *);
+
+static int ext2_xattr_cache_insert(struct buffer_head *);
+static struct buffer_head *ext2_xattr_cache_find(struct inode *,
+						 struct ext2_xattr_header *);
+static void ext2_xattr_cache_remove(struct buffer_head *);
+static void ext2_xattr_rehash(struct ext2_xattr_header *,
+			      struct ext2_xattr_entry *);
+
+static struct mb_cache *ext2_xattr_cache;
+
+/*
+ * If a file system does not share extended attributes among inodes,
+ * we should not need the ext2_xattr_sem semaphore. However, the
+ * filesystem may still contain shared blocks, so we always take
+ * the lock.
+ */
+
+static DECLARE_MUTEX(ext2_xattr_sem);
+static struct ext2_xattr_handler *ext2_xattr_handlers[EXT2_XATTR_INDEX_MAX];
+static rwlock_t ext2_handler_lock = RW_LOCK_UNLOCKED;
+
+int
+ext2_xattr_register(int name_index, struct ext2_xattr_handler *handler)
+{
+	int error = -EINVAL;
+
+	if (name_index > 0 && name_index <= EXT2_XATTR_INDEX_MAX) {
+		write_lock(&ext2_handler_lock);
+		if (!ext2_xattr_handlers[name_index-1]) {
+			ext2_xattr_handlers[name_index-1] = handler;
+			error = 0;
+		}
+		write_unlock(&ext2_handler_lock);
+	}
+	return error;
+}
+
+void
+ext2_xattr_unregister(int name_index, struct ext2_xattr_handler *handler)
+{
+	if (name_index > 0 || name_index <= EXT2_XATTR_INDEX_MAX) {
+		write_lock(&ext2_handler_lock);
+		ext2_xattr_handlers[name_index-1] = NULL;
+		write_unlock(&ext2_handler_lock);
+	}
+}
+
+static inline const char *
+strcmp_prefix(const char *a, const char *a_prefix)
+{
+	while (*a_prefix && *a == *a_prefix) {
+		a++;
+		a_prefix++;
+	}
+	return *a_prefix ? NULL : a;
+}
+
+/*
+ * Decode the extended attribute name, and translate it into
+ * the name_index and name suffix.
+ */
+static struct ext2_xattr_handler *
+ext2_xattr_resolve_name(const char **name)
+{
+	struct ext2_xattr_handler *handler = NULL;
+	int i;
+
+	if (!*name)
+		return NULL;
+	read_lock(&ext2_handler_lock);
+	for (i=0; i<EXT2_XATTR_INDEX_MAX; i++) {
+		if (ext2_xattr_handlers[i]) {
+			const char *n = strcmp_prefix(*name,
+				ext2_xattr_handlers[i]->prefix);
+			if (n) {
+				handler = ext2_xattr_handlers[i];
+				*name = n;
+				break;
+			}
+		}
+	}
+	read_unlock(&ext2_handler_lock);
+	return handler;
+}
+
+static inline struct ext2_xattr_handler *
+ext2_xattr_handler(int name_index)
+{
+	struct ext2_xattr_handler *handler = NULL;
+	if (name_index > 0 && name_index <= EXT2_XATTR_INDEX_MAX) {
+		read_lock(&ext2_handler_lock);
+		handler = ext2_xattr_handlers[name_index-1];
+		read_unlock(&ext2_handler_lock);
+	}
+	return handler;
+}
+
+/*
+ * Inode operation getxattr()
+ *
+ * dentry->d_inode->i_sem down
+ * BKL held [before 2.5.x]
+ */
+ssize_t
+ext2_getxattr(struct dentry *dentry, const char *name,
+	      void *buffer, size_t size)
+{
+	struct ext2_xattr_handler *handler;
+	struct inode *inode = dentry->d_inode;
+
+	handler = ext2_xattr_resolve_name(&name);
+	if (!handler)
+		return -EOPNOTSUPP;
+	return handler->get(inode, name, buffer, size);
+}
+
+/*
+ * Inode operation listxattr()
+ *
+ * dentry->d_inode->i_sem down
+ * BKL held [before 2.5.x]
+ */
+ssize_t
+ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+	return ext2_xattr_list(dentry->d_inode, buffer, size);
+}
+
+/*
+ * Inode operation setxattr()
+ *
+ * dentry->d_inode->i_sem down
+ * BKL held [before 2.5.x]
+ */
+int
+ext2_setxattr(struct dentry *dentry, const char *name,
+	      void *value, size_t size, int flags)
+{
+	struct ext2_xattr_handler *handler;
+	struct inode *inode = dentry->d_inode;
+
+	if (size == 0)
+		value = "";  /* empty EA, do not remove */
+	handler = ext2_xattr_resolve_name(&name);
+	if (!handler)
+		return -EOPNOTSUPP;
+	return handler->set(inode, name, value, size, flags);
+}
+
+/*
+ * Inode operation removexattr()
+ *
+ * dentry->d_inode->i_sem down
+ * BKL held [before 2.5.x]
+ */
+int
+ext2_removexattr(struct dentry *dentry, const char *name)
+{
+	struct ext2_xattr_handler *handler;
+	struct inode *inode = dentry->d_inode;
+
+	handler = ext2_xattr_resolve_name(&name);
+	if (!handler)
+		return -EOPNOTSUPP;
+	return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
+}
+
+/*
+ * 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;
+	unsigned int size;
+	char *end;
+	int name_len, error;
+
+	ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
+		  name_index, name, buffer, (long)buffer_size);
+
+	if (name == NULL)
+		return -EINVAL;
+	if (!EXT2_I(inode)->i_file_acl)
+		return -ENODATA;
+	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
+	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
+	if (!bh)
+		return -EIO;
+	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 */
+	name_len = strlen(name);
+
+	error = -ERANGE;
+	if (name_len > 255)
+		goto cleanup;
+	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;
+	}
+	/* Check the remaining name entries */
+	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(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(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);
+
+	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.
+ */
+int
+ext2_xattr_list(struct inode *inode, char *buffer, size_t buffer_size)
+{
+	struct buffer_head *bh = NULL;
+	struct ext2_xattr_entry *entry;
+	unsigned int size = 0;
+	char *buf, *end;
+	int error;
+
+	ea_idebug(inode, "buffer=%p, buffer_size=%ld",
+		  buffer, (long)buffer_size);
+
+	if (!EXT2_I(inode)->i_file_acl)
+		return 0;
+	ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
+	bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
+	if (!bh)
+		return -EIO;
+	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;
+	}
+	/* compute the size required for the list of attribute names */
+	for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
+	     entry = EXT2_XATTR_NEXT(entry)) {
+		struct ext2_xattr_handler *handler;
+		struct ext2_xattr_entry *next =
+			EXT2_XATTR_NEXT(entry);
+		if ((char *)next >= end)
+			goto bad_block;
+
+		handler = ext2_xattr_handler(entry->e_name_index);
+		if (handler) {
+			size += handler->list(NULL, inode, entry->e_name,
+					      entry->e_name_len) + 1;
+		}
+	}
+
+	if (ext2_xattr_cache_insert(bh))
+		ea_idebug(inode, "cache insert failed");
+	if (!buffer) {
+		error = size;
+		goto cleanup;
+	} else {
+		error = -ERANGE;
+		if (size > buffer_size)
+			goto cleanup;
+	}
+
+	/* list the attribute names */
+	buf = buffer;
+	for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
+	     entry = EXT2_XATTR_NEXT(entry)) {
+		struct ext2_xattr_handler *handler;
+		
+		handler = ext2_xattr_handler(entry->e_name_index);
+		if (handler) {
+			buf += handler->list(buf, inode, entry->e_name,
+					     entry->e_name_len);
+			*buf++ = '\0';
+		}
+	}
+	error = size;
+
+cleanup:
+	brelse(bh);
+
+	return error;
+}
+
+/*
+ * 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;
+
+	lock_super(sb);
+	EXT2_SB(sb)->s_es->s_feature_compat |=
+		cpu_to_le32(EXT2_FEATURE_COMPAT_EXT_ATTR);
+	sb->s_dirt = 1;
+	mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
+	unlock_super(sb);
+}
+
+/*
+ * ext2_xattr_set()
+ *
+ * Create, replace or remove an extended attribute for this inode. Buffer
+ * 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;
+	unsigned int name_len;
+	int min_offs = sb->s_blocksize, not_found = 1, free, 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 (IS_RDONLY(inode))
+		return -EROFS;
+	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+		return -EPERM;
+	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(&ext2_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) {
+				int 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) {
+				int 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
+			free -= EXT2_XATTR_LEN(name_len);
+	} else {
+		/* Request to create an existing attribute? */
+		error = -EEXIST;
+		if (flags & XATTR_CREATE)
+			goto cleanup;
+		if (!here->e_value_block && here->e_value_size) {
+			unsigned int 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_SIZE(value_len);
+	error = -ENOSPC;
+	if (free < 0)
+		goto cleanup;
+
+	/* Here we know that we can set the new attribute. */
+
+	if (header) {
+		if (header->h_refcount == cpu_to_le32(1)) {
+			ea_bdebug(bh, "modifying in-place");
+			ext2_xattr_cache_remove(bh);
+		} else {
+			int offset;
+
+			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 *)header - bh->b_data;
+			here = ENTRY((char *)here + offset);
+			last = ENTRY((char *)last + offset);
+		}
+	} else {
+		/* Allocate a buffer where we construct the new block. */
+		header = kmalloc(sb->s_blocksize, GFP_KERNEL);
+		error = -ENOMEM;
+		if (header == NULL)
+			goto cleanup;
+		memset(header, 0, sb->s_blocksize);
+		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);
+	}
+
+	if (not_found) {
+		/* Insert the new name. */
+		int size = EXT2_XATTR_LEN(name_len);
+		int 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 {
+		/* Remove the old value. */
+		if (!here->e_value_block && here->e_value_size) {
+			char *first_val = (char *)header + min_offs;
+			int 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));
+			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)) {
+				int 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 this attribute. */
+			if (EXT2_XATTR_NEXT(ENTRY(header+1)) == last) {
+				/* This block is now empty. */
+				error = ext2_xattr_set2(inode, bh, NULL);
+				goto cleanup;
+			} else {
+				/* Remove the old name. */
+				int 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);
+		}
+	}
+	ext2_xattr_rehash(header, here);
+
+	error = ext2_xattr_set2(inode, bh, header);
+
+cleanup:
+	brelse(bh);
+	if (!(bh && header == HDR(bh)))
+		kfree(header);
+	up(&ext2_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;
+
+	if (header) {
+		new_bh = ext2_xattr_cache_find(inode, header);
+		if (new_bh) {
+			/*
+			 * We found an identical block in the cache.
+			 * The old block will be released after updating
+			 * the inode.
+			 */
+			ea_bdebug(old_bh, "reusing block %ld",
+				new_bh->b_blocknr);
+			
+			error = -EDQUOT;
+			if (DQUOT_ALLOC_BLOCK(inode, 1))
+				goto cleanup;
+			
+			HDR(new_bh)->h_refcount = cpu_to_le32(
+				le32_to_cpu(HDR(new_bh)->h_refcount) + 1);
+			ea_bdebug(new_bh, "refcount now=%d",
+				le32_to_cpu(HDR(new_bh)->h_refcount));
+		} else if (old_bh && header == HDR(old_bh)) {
+			/* Keep this block. */
+			new_bh = old_bh;
+			ext2_xattr_cache_insert(new_bh);
+		} else {
+			/* We need to allocate a new block */
+			int goal = le32_to_cpu(EXT2_SB(sb)->s_es->s_first_data_block) +
+				EXT2_I(inode)->i_block_group * EXT2_BLOCKS_PER_GROUP(sb);
+			int block = ext2_new_block(inode, goal, 0, 0, &error);
+			if (error)
+				goto cleanup;
+			ea_idebug(inode, "creating block %d", block);
+
+			new_bh = sb_getblk(sb, block);
+			if (!new_bh) {
+				ext2_free_blocks(inode, block, 1);
+				error = -EIO;
+				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(new_bh);
+			
+			ext2_xattr_update_super_block(sb);
+		}
+		mark_buffer_dirty(new_bh);
+		if (IS_SYNC(inode)) {
+			ll_rw_block(WRITE, 1, &new_bh);
+			wait_on_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;
+	if (IS_SYNC(inode)) {
+		error = ext2_sync_inode (inode);
+		if (error)
+			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 not still using it,
+		 * we now release the old block.
+		*/
+		unsigned int refcount = le32_to_cpu(HDR(old_bh)->h_refcount);
+
+		if (refcount == 1) {
+			/* Free the old block. */
+			ea_bdebug(old_bh, "freeing");
+			ext2_free_blocks(inode, old_bh->b_blocknr, 1);
+			/* 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. */
+			refcount--;
+			HDR(old_bh)->h_refcount = cpu_to_le32(refcount);
+			DQUOT_FREE_BLOCK(inode, 1);
+			mark_buffer_dirty(old_bh);
+			ea_bdebug(old_bh, "refcount now=%d", refcount);
+		}
+	}
+
+cleanup:
+	if (old_bh != new_bh)
+		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;
+
+	if (!EXT2_I(inode)->i_file_acl)
+		return;
+	down(&ext2_xattr_sem);
+
+	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;
+	}
+	ea_bdebug(bh, "refcount now=%d", le32_to_cpu(HDR(bh)->h_refcount) - 1);
+	if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
+		ext2_xattr_cache_remove(bh);
+		ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
+		bforget(bh);
+		bh = NULL;
+	} else {
+		HDR(bh)->h_refcount = cpu_to_le32(
+			le32_to_cpu(HDR(bh)->h_refcount) - 1);
+		mark_buffer_dirty(bh);
+		if (IS_SYNC(inode)) {
+			ll_rw_block(WRITE, 1, &bh);
+			wait_on_buffer(bh);
+		}
+		DQUOT_FREE_BLOCK(inode, 1);
+	}
+	EXT2_I(inode)->i_file_acl = 0;
+
+cleanup:
+	brelse(bh);
+	up(&ext2_xattr_sem);
+}
+
+/*
+ * ext2_xattr_put_super()
+ *
+ * This is called when a file system is unmounted.
+ */
+void
+ext2_xattr_put_super(struct super_block *sb)
+{
+	mb_cache_shrink(ext2_xattr_cache, sb->s_bdev);
+}
+
+
+/*
+ * 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 buffer_head *bh)
+{
+	__u32 hash = le32_to_cpu(HDR(bh)->h_hash);
+	struct mb_cache_entry *ce;
+	int error;
+
+	ce = mb_cache_entry_alloc(ext2_xattr_cache);
+	if (!ce)
+		return -ENOMEM;
+	error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
+	if (error) {
+		mb_cache_entry_free(ce);
+		if (error == -EBUSY) {
+			ea_bdebug(bh, "already in cache (%d cache entries)",
+				atomic_read(&ext2_xattr_cache->c_entry_count));
+			error = 0;
+		}
+	} else {
+		ea_bdebug(bh, "inserting [%x] (%d cache entries)", (int)hash,
+			  atomic_read(&ext2_xattr_cache->c_entry_count));
+		mb_cache_entry_release(ce);
+	}
+	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_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 pointer 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;
+
+	if (!header->h_hash)
+		return NULL;  /* never share */
+	ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
+	ce = mb_cache_entry_find_first(ext2_xattr_cache, 0, inode->i_bdev, hash);
+	while (ce) {
+		struct buffer_head *bh = sb_bread(inode->i_sb, ce->e_block);
+
+		if (!bh) {
+			ext2_error(inode->i_sb, "ext2_xattr_cache_find",
+				"inode %ld: block %ld read error",
+				inode->i_ino, (unsigned long) ce->e_block);
+		} 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_block,
+				  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_release(ce);
+			return bh;
+		}
+		brelse(bh);
+		ce = mb_cache_entry_find_next(ce, 0, inode->i_bdev, hash);
+	}
+	return NULL;
+}
+
+/*
+ * ext2_xattr_cache_remove()
+ *
+ * Remove the cache entry of a block from the cache. Called when a
+ * block becomes invalid.
+ */
+static void
+ext2_xattr_cache_remove(struct buffer_head *bh)
+{
+	struct mb_cache_entry *ce;
+
+	ce = mb_cache_entry_get(ext2_xattr_cache, bh->b_bdev, bh->b_blocknr);
+	if (ce) {
+		ea_bdebug(bh, "removing (%d cache entries remaining)",
+			  atomic_read(&ext2_xattr_cache->c_entry_count)-1);
+		mb_cache_entry_free(ce);
+	} else 
+		ea_bdebug(bh, "no cache entry");
+}
+
+#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) {
+		__u32 *value = (__u32 *)((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
+
+int __init
+init_ext2_xattr(void)
+{
+	int	err;
+	
+	err = ext2_xattr_register(EXT2_XATTR_INDEX_USER, &ext2_xattr_user_handler);
+	if (err)
+		return err;
+	ext2_xattr_cache = mb_cache_create("ext2_xattr", NULL,
+		sizeof(struct mb_cache_entry) +
+		sizeof(struct mb_cache_entry_index), 1, 6);
+	if (!ext2_xattr_cache) {
+		ext2_xattr_unregister(EXT2_XATTR_INDEX_USER, &ext2_xattr_user_handler);
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+void
+exit_ext2_xattr(void)
+{
+	mb_cache_destroy(ext2_xattr_cache);
+	ext2_xattr_unregister(EXT2_XATTR_INDEX_USER, &ext2_xattr_user_handler);
+}