Release 4.10 fs/ext4/xattr.c

/*
 * linux/fs/ext4/xattr.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
 *
 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
 * Ext4 code with a lot of help from Eric Jarman <ejarman@acm.org>.
 * 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.
 * ea-in-inode support by Alex Tomas <alex@clusterfs.com> aka bzzz
 *  and Andreas Gruenbacher <agruen@suse.de>.
 */

/*
 * Extended attributes are stored directly in inodes (on file systems with
 * inodes bigger than 128 bytes) and on additional disk blocks. The i_file_acl
 * field contains the block number if an inode uses an additional block. All
 * attributes must fit in the inode and one additional block. Blocks that
 * contain the identical set of attributes may be shared among several inodes.
 * Identical blocks are detected by keeping a cache of blocks that have
 * recently been accessed.
 *
 * The attributes in inodes and on blocks have a different header; the entries
 * are stored in the same format:
 *
 *   +------------------+
 *   | header           |
 *   | entry 1          | |
 *   | entry 2          | | growing downwards
 *   | entry 3          | v
 *   | four null bytes  |
 *   | . . .            |
 *   | value 1          | ^
 *   | value 3          | | growing upwards
 *   | value 2          | |
 *   +------------------+
 *
 * The header is followed by multiple entry descriptors. In disk blocks, the
 * entry descriptors are kept sorted. In inodes, they are unsorted. The
 * attribute values are aligned to the end of the block in no specific order.
 *
 * Locking strategy
 * ----------------
 * EXT4_I(inode)->i_file_acl is protected by EXT4_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 can change. Multiple writers to the same block are synchronized
 * by the buffer lock.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/mbcache.h>
#include <linux/quotaops.h>
#include "ext4_jbd2.h"
#include "ext4.h"
#include "xattr.h"
#include "acl.h"

#ifdef EXT4_XATTR_DEBUG

# define ea_idebug(inode, fmt, ...)					\
	printk(KERN_DEBUG "inode %s:%lu: " fmt "\n",                    \
               inode->i_sb->s_id, inode->i_ino, ##__VA_ARGS__)

# define ea_bdebug(bh, fmt, ...)					\
	printk(KERN_DEBUG "block %pg:%lu: " fmt "\n",                   \
               bh->b_bdev, (unsigned long)bh->b_blocknr, ##__VA_ARGS__)
#else

# define ea_idebug(inode, fmt, ...)	no_printk(fmt, ##__VA_ARGS__)

# define ea_bdebug(bh, fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
#endif

static void ext4_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
static struct buffer_head *ext4_xattr_cache_find(struct inode *,
						 struct ext4_xattr_header *,
						 struct mb_cache_entry **);
static void ext4_xattr_rehash(struct ext4_xattr_header *,
			      struct ext4_xattr_entry *);
static int ext4_xattr_list(struct dentry *dentry, char *buffer,
			   size_t buffer_size);


static const struct xattr_handler *ext4_xattr_handler_map[] = {
	[EXT4_XATTR_INDEX_USER]		     = &ext4_xattr_user_handler,
#ifdef CONFIG_EXT4_FS_POSIX_ACL
	[EXT4_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
	[EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
#endif
	[EXT4_XATTR_INDEX_TRUSTED]	     = &ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4_FS_SECURITY
	[EXT4_XATTR_INDEX_SECURITY]	     = &ext4_xattr_security_handler,
#endif
};


const struct xattr_handler *ext4_xattr_handlers[] = {
	&ext4_xattr_user_handler,
	&ext4_xattr_trusted_handler,
#ifdef CONFIG_EXT4_FS_POSIX_ACL
	&posix_acl_access_xattr_handler,
	&posix_acl_default_xattr_handler,
#endif
#ifdef CONFIG_EXT4_FS_SECURITY
	&ext4_xattr_security_handler,
#endif
	NULL
};


#define EXT4_GET_MB_CACHE(inode)	(((struct ext4_sb_info *) \
                                inode->i_sb->s_fs_info)->s_mb_cache)



static __le32 ext4_xattr_block_csum(struct inode *inode,
				    sector_t block_nr,
				    struct ext4_xattr_header *hdr)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	__u32 csum;
	__le64 dsk_block_nr = cpu_to_le64(block_nr);
	__u32 dummy_csum = 0;
	int offset = offsetof(struct ext4_xattr_header, h_checksum);

	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&dsk_block_nr,
			   sizeof(dsk_block_nr));
	csum = ext4_chksum(sbi, csum, (__u8 *)hdr, offset);
	csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, sizeof(dummy_csum));
	offset += sizeof(dummy_csum);
	csum = ext4_chksum(sbi, csum, (__u8 *)hdr + offset,
			   EXT4_BLOCK_SIZE(inode->i_sb) - offset);

	return cpu_to_le32(csum);
}

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darrick j. wong
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daeho jeong
daeho jeong
64
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theodore tso
theodore tso
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static int ext4_xattr_block_csum_verify(struct inode *inode,
					sector_t block_nr,
					struct ext4_xattr_header *hdr)
{
	if (ext4_has_metadata_csum(inode->i_sb) &&
	    (hdr->h_checksum != ext4_xattr_block_csum(inode, block_nr, hdr)))
		return 0;
	return 1;
}

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darrick j. wong
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dmitriy monakhov
dmitriy monakhov
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static void ext4_xattr_block_csum_set(struct inode *inode,
				      sector_t block_nr,
				      struct ext4_xattr_header *hdr)
{
	if (!ext4_has_metadata_csum(inode->i_sb))
		return;

	hdr->h_checksum = ext4_xattr_block_csum(inode, block_nr, hdr);
}

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darrick j. wong
darrick j. wong
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dmitriy monakhov
dmitriy monakhov
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static inline int ext4_handle_dirty_xattr_block(handle_t *handle,
						struct inode *inode,
						struct buffer_head *bh)
{
	ext4_xattr_block_csum_set(inode, bh->b_blocknr, BHDR(bh));
	return ext4_handle_dirty_metadata(handle, inode, bh);
}

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darrick j. wong
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static inline const struct xattr_handler *

ext4_xattr_handler(int name_index)
{
	const struct xattr_handler *handler = NULL;

	if (name_index > 0 && name_index < ARRAY_SIZE(ext4_xattr_handler_map))
		handler = ext4_xattr_handler_map[name_index];
	return handler;
}

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dave kleikamp
dave kleikamp
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1
33.33%
mingming cao
mingming cao
3
6.82%
1
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stephen hemminger
stephen hemminger
2
4.55%
1
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/*
 * Inode operation listxattr()
 *
 * d_inode(dentry)->i_mutex: don't care
 */

ssize_t

ext4_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
	return ext4_xattr_list(dentry, buffer, size);
}

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dave kleikamp
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mingming cao
mingming cao
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static int

ext4_xattr_check_names(struct ext4_xattr_entry *entry, void *end,
		       void *value_start)
{
	struct ext4_xattr_entry *e = entry;

	/* Find the end of the names list */
	while (!IS_LAST_ENTRY(e)) {
		struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(e);
		if ((void *)next >= end)
			return -EFSCORRUPTED;
		e = next;
	}

	/* Check the values */
	while (!IS_LAST_ENTRY(entry)) {
		if (entry->e_value_block != 0)
			return -EFSCORRUPTED;
		if (entry->e_value_size != 0) {
			u16 offs = le16_to_cpu(entry->e_value_offs);
			u32 size = le32_to_cpu(entry->e_value_size);
			void *value;

			/*
                         * The value cannot overlap the names, and the value
                         * with padding cannot extend beyond 'end'.  Check both
                         * the padded and unpadded sizes, since the size may
                         * overflow to 0 when adding padding.
                         */
			if (offs > end - value_start)
				return -EFSCORRUPTED;
			value = value_start + offs;
			if (value < (void *)e + sizeof(u32) ||
			    size > end - value ||
			    EXT4_XATTR_SIZE(size) > end - value)
				return -EFSCORRUPTED;
		}
		entry = EXT4_XATTR_NEXT(entry);
	}

	return 0;
}

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darrick j. wong
darrick j. wong
65
35.14%
2
33.33%
eric biggers
eric biggers
56
30.27%
1
16.67%
dave kleikamp
dave kleikamp
48
25.95%
1
16.67%
jan kara
jan kara
12
6.49%
1
16.67%
mingming cao
mingming cao
4
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1
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static inline int

ext4_xattr_check_block(struct inode *inode, struct buffer_head *bh)
{
	int error;

	if (buffer_verified(bh))
		return 0;

	if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
	    BHDR(bh)->h_blocks != cpu_to_le32(1))
		return -EFSCORRUPTED;
	if (!ext4_xattr_block_csum_verify(inode, bh->b_blocknr, BHDR(bh)))
		return -EFSBADCRC;
	error = ext4_xattr_check_names(BFIRST(bh), bh->b_data + bh->b_size,
				       bh->b_data);
	if (!error)
		set_buffer_verified(bh);
	return error;
}

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darrick j. wong
darrick j. wong
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dave kleikamp
dave kleikamp
54
46.55%
1
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mingming cao
mingming cao
3
2.59%
1
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zheng liu
zheng liu
1
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1
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static int

__xattr_check_inode(struct inode *inode, struct ext4_xattr_ibody_header *header,
			 void *end, const char *function, unsigned int line)
{
	int error = -EFSCORRUPTED;

	if (end - (void *)header < sizeof(*header) + sizeof(u32) ||
	    (header->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC)))
		goto errout;
	error = ext4_xattr_check_names(IFIRST(header), end, IFIRST(header));
errout:
	if (error)
		__ext4_error_inode(inode, function, line, 0,
				   "corrupted in-inode xattr");
	return error;
}

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theodore tso
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eric biggers
eric biggers
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dave kleikamp
dave kleikamp
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#define xattr_check_inode(inode, header, end) \
	__xattr_check_inode((inode), (header), (end), __func__, __LINE__)


static inline int

ext4_xattr_check_entry(struct ext4_xattr_entry *entry, size_t size)
{
	size_t value_size = le32_to_cpu(entry->e_value_size);

	if (entry->e_value_block != 0 || value_size > size ||
	    le16_to_cpu(entry->e_value_offs) + value_size > size)
		return -EFSCORRUPTED;
	return 0;
}

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dave kleikamp
dave kleikamp
51
92.73%
1
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mingming cao
mingming cao
2
3.64%
1
25.00%
theodore tso
theodore tso
1
1.82%
1
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darrick j. wong
darrick j. wong
1
1.82%
1
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55
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4
100.00%


static int

ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
		      const char *name, size_t size, int sorted)
{
	struct ext4_xattr_entry *entry;
	size_t name_len;
	int cmp = 1;

	if (name == NULL)
		return -EINVAL;
	name_len = strlen(name);
	entry = *pentry;
	for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
		cmp = name_index - entry->e_name_index;
		if (!cmp)
			cmp = name_len - entry->e_name_len;
		if (!cmp)
			cmp = memcmp(name, entry->e_name, name_len);
		if (cmp <= 0 && (sorted || cmp == 0))
			break;
	}
	*pentry = entry;
	if (!cmp && ext4_xattr_check_entry(entry, size))
		return -EFSCORRUPTED;
	return cmp ? -ENODATA : 0;
}

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dave kleikamp
dave kleikamp
156
96.30%
1
33.33%
mingming cao
mingming cao
5
3.09%
1
33.33%
darrick j. wong
darrick j. wong
1
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1
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static int

ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
		     void *buffer, size_t buffer_size)
{
	struct buffer_head *bh = NULL;
	struct ext4_xattr_entry *entry;
	size_t size;
	int error;
	struct mb_cache *ext4_mb_cache = EXT4_GET_MB_CACHE(inode);

	ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
		  name_index, name, buffer, (long)buffer_size);

	error = -ENODATA;
	if (!EXT4_I(inode)->i_file_acl)
		goto cleanup;
	ea_idebug(inode, "reading block %llu",
		  (unsigned long long)EXT4_I(inode)->i_file_acl);
	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
	if (!bh)
		goto cleanup;
	ea_bdebug(bh, "b_count=%d, refcount=%d",
		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
	if (ext4_xattr_check_block(inode, bh)) {
bad_block:
		EXT4_ERROR_INODE(inode, "bad block %llu",
				 EXT4_I(inode)->i_file_acl);
		error = -EFSCORRUPTED;
		goto cleanup;
	}
	ext4_xattr_cache_insert(ext4_mb_cache, bh);
	entry = BFIRST(bh);
	error = ext4_xattr_find_entry(&entry, name_index, name, bh->b_size, 1);
	if (error == -EFSCORRUPTED)
		goto bad_block;
	if (error)
		goto cleanup;
	size = le32_to_cpu(entry->e_value_size);
	if (buffer) {
		error = -ERANGE;
		if (size > buffer_size)
			goto cleanup;
		memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
		       size);
	}
	error = size;

cleanup:
	brelse(bh);
	return error;
}

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dave kleikamp
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t makphaibulchoke
t makphaibulchoke
11
3.61%
1
12.50%
mingming cao
mingming cao
9
2.95%
1
12.50%
joe perches
joe perches
6
1.97%
1
12.50%
darrick j. wong
darrick j. wong
4
1.31%
2
25.00%
theodore tso
theodore tso
2
0.66%
1
12.50%
jan kara
jan kara
1
0.33%
1
12.50%
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305
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8
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int

ext4_xattr_ibody_get(struct inode *inode, int name_index, const char *name,
		     void *buffer, size_t buffer_size)
{
	struct ext4_xattr_ibody_header *header;
	struct ext4_xattr_entry *entry;
	struct ext4_inode *raw_inode;
	struct ext4_iloc iloc;
	size_t size;
	void *end;
	int error;

	if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR))
		return -ENODATA;
	error = ext4_get_inode_loc(inode, &iloc);
	if (error)
		return error;
	raw_inode = ext4_raw_inode(&iloc);
	header = IHDR(inode, raw_inode);
	entry = IFIRST(header);
	end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
	error = xattr_check_inode(inode, header, end);
	if (error)
		goto cleanup;
	error = ext4_xattr_find_entry(&entry, name_index, name,
				      end - (void *)entry, 0);
	if (error)
		goto cleanup;
	size = le32_to_cpu(entry->e_value_size);
	if (buffer) {
		error = -ERANGE;
		if (size > buffer_size)
			goto cleanup;
		memcpy(buffer, (void *)IFIRST(header) +
		       le16_to_cpu(entry->e_value_offs), size);
	}
	error = size;

cleanup:
	brelse(iloc.bh);
	return error;
}

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dave kleikamp
dave kleikamp
223
92.53%
1
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mingming cao
mingming cao
10
4.15%
1
20.00%
theodore tso
theodore tso
7
2.90%
2
40.00%
darrick j. wong
darrick j. wong
1
0.41%
1
20.00%
Total
241
100.00%
5
100.00%

/*
 * ext4_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

ext4_xattr_get(struct inode *inode, int name_index, const char *name,
	       void *buffer, size_t buffer_size)
{
	int error;

	if (strlen(name) > 255)
		return -ERANGE;

	down_read(&EXT4_I(inode)->xattr_sem);
	error = ext4_xattr_ibody_get(inode, name_index, name, buffer,
				     buffer_size);
	if (error == -ENODATA)
		error = ext4_xattr_block_get(inode, name_index, name, buffer,
					     buffer_size);
	up_read(&EXT4_I(inode)->xattr_sem);
	return error;
}

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dave kleikamp
dave kleikamp
85
82.52%
1
33.33%
zhang zhen
zhang zhen
13
12.62%
1
33.33%
mingming cao
mingming cao
5
4.85%
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103
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static int

ext4_xattr_list_entries(struct dentry *dentry, struct ext4_xattr_entry *entry,
			char *buffer, size_t buffer_size)
{
	size_t rest = buffer_size;

	for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
		const struct xattr_handler *handler =
			ext4_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)
					return -ERANGE;
				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;
		}
	}
	return buffer_size - rest;  /* total size */
}

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dave kleikamp
dave kleikamp
94
53.41%
1
16.67%
andreas gruenbacher
andreas gruenbacher
75
42.61%
2
33.33%
mingming cao
mingming cao
4
2.27%
1
16.67%
christoph hellwig
christoph hellwig
2
1.14%
1
16.67%
stephen hemminger
stephen hemminger
1
0.57%
1
16.67%
Total
176
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6
100.00%


static int

ext4_xattr_block_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	struct inode *inode = d_inode(dentry);
	struct buffer_head *bh = NULL;
	int error;
	struct mb_cache *ext4_mb_cache = EXT4_GET_MB_CACHE(inode);

	ea_idebug(inode, "buffer=%p, buffer_size=%ld",
		  buffer, (long)buffer_size);

	error = 0;
	if (!EXT4_I(inode)->i_file_acl)
		goto cleanup;
	ea_idebug(inode, "reading block %llu",
		  (unsigned long long)EXT4_I(inode)->i_file_acl);
	bh = sb_bread(inode->i_sb, EXT4_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(BHDR(bh)->h_refcount));
	if (ext4_xattr_check_block(inode, bh)) {
		EXT4_ERROR_INODE(inode, "bad block %llu",
				 EXT4_I(inode)->i_file_acl);
		error = -EFSCORRUPTED;
		goto cleanup;
	}
	ext4_xattr_cache_insert(ext4_mb_cache, bh);
	error = ext4_xattr_list_entries(dentry, BFIRST(bh), buffer, buffer_size);

cleanup:
	brelse(bh);

	return error;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dave kleikamp
dave kleikamp
176
80.00%
1
10.00%
t makphaibulchoke
t makphaibulchoke
11
5.00%
1
10.00%
christoph hellwig
christoph hellwig
10
4.55%
1
10.00%
mingming cao
mingming cao
8
3.64%
1
10.00%
joe perches
joe perches
6
2.73%
1
10.00%
david howells
david howells
3
1.36%
1
10.00%
darrick j. wong
darrick j. wong
3
1.36%
2
20.00%
theodore tso
theodore tso
2
0.91%
1
10.00%
jan kara
jan kara
1
0.45%
1
10.00%
Total
220
100.00%
10
100.00%


static int

ext4_xattr_ibody_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	struct inode *inode = d_inode(dentry);
	struct ext4_xattr_ibody_header *header;
	struct ext4_inode *raw_inode;
	struct ext4_iloc iloc;
	void *end;
	int error;

	if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR))
		return 0;
	error = ext4_get_inode_loc(inode, &iloc);
	if (error)
		return error;
	raw_inode = ext4_raw_inode(&iloc);
	header = IHDR(inode, raw_inode);
	end = (void *)raw_inode + EXT4_SB(inode->i_sb)->s_inode_size;
	error = xattr_check_inode(inode, header, end);
	if (error)
		goto cleanup;
	error = ext4_xattr_list_entries(dentry, IFIRST(header),
					buffer, buffer_size);

cleanup:
	brelse(iloc.bh);
	return error;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dave kleikamp
dave kleikamp
131
82.39%
1
16.67%
christoph hellwig
christoph hellwig
10
6.29%
1
16.67%
mingming cao
mingming cao
9
5.66%
1
16.67%
theodore tso
theodore tso
6
3.77%
2
33.33%
david howells
david howells
3
1.89%
1
16.67%
Total
159
100.00%
6
100.00%

/*
 * ext4_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

ext4_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	int ret, ret2;

	down_read(&EXT4_I(d_inode(dentry))->xattr_sem);
	ret = ret2 = ext4_xattr_ibody_list(dentry, buffer, buffer_size);
	if (ret < 0)
		goto errout;
	if (buffer) {
		buffer += ret;
		buffer_size -= ret;
	}
	ret = ext4_xattr_block_list(dentry, buffer, buffer_size);
	if (ret < 0)
		goto errout;
	ret += ret2;
errout:
	up_read(&EXT4_I(d_inode(dentry))->xattr_sem);
	return ret;
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dave kleikamp
dave kleikamp
76
65.52%
1
16.67%
theodore tso
theodore tso
22
18.97%
1
16.67%
david howells
david howells
6
5.17%
1
16.67%
christoph hellwig
christoph hellwig
6
5.17%
1
16.67%
mingming cao
mingming cao
6
5.17%
2
33.33%
Total
116
100.00%
6
100.00%

/*
 * If the EXT4_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 * not set, set it.
 */


static void ext4_xattr_update_super_block(handle_t *handle,
					  struct super_block *sb)
{
	if (ext4_has_feature_xattr(sb))
		return;

	BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
	if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) {
		ext4_set_feature_xattr(sb);
		ext4_handle_dirty_super(handle, sb);
	}
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
dave kleikamp
dave kleikamp
47
72.31%
1
20.00%
liang xie
liang xie
12
18.46%
1
20.00%
mingming cao
mingming cao
3
4.62%
1
20.00%
darrick j. wong
darrick j. wong
2
3.08%
1
20.00%
theodore tso
theodore tso
1
1.54%
1
20.00%
Total
65
100.00%
5
100.00%

/*
 * Release the xattr block BH: If the reference count is > 1, decrement it;
 * otherwise free the block.
 */

static void

ext4_xattr_release_block(handle_t *handle, struct inode *inode,
			 struct buffer_head *bh)
{
	struct mb_cache *ext4_mb_cache = EXT4_GET_MB_CACHE(inode);
	u32 hash, ref;
	int error = 0;

	BUFFER_TRACE(bh, "get_write_access");
	error = ext4_journal_get_write_access(handle, bh);
	if (error)
		goto out;

	lock_buffer(bh);
	hash = le32_to_cpu(BHDR(bh)->h_hash);
	ref = le32_to_cpu(BHDR(bh)->h_refcount);
	if (ref == 1) {
		ea_bdebug(bh, "refcount now=0; freeing");
		/*
                 * This must happen under buffer lock for
                 * ext4_xattr_block_set() to reliably detect freed block
                 */
		mb_cache_entry_delete_block(ext4_mb_cache, hash, bh->b_blocknr);
		get_bh(bh);
		unlock_buffer(bh);
		ext4_free_blocks(handle, inode, bh, 0, 1,
				 EXT4_FREE_BLOCKS_METADATA |
				 EXT4_FREE_BLOCKS_FORGET);
	} else {
		ref--;
		BHDR(bh)->h_refcount = cpu_to_le32(ref);
		if (ref == EXT4_XATTR_REFCOUNT_MAX - 1) {
			struct mb_cache_entry *ce;

			ce = mb_cache_entry_get(ext4_mb_cache, hash,
						bh->b_blocknr);
			if (ce) {
				ce->e_reusable = 1;
				mb_cache_entry_put(ext4_mb_cache, ce);
			}
		}

		/*
                 * Beware of this ugliness: Releasing of xattr block references
                 * from different inodes can race and so we have to protect
                 * from a race where someone else frees the block (and releases
                 * its journal_head) before we are done dirtying the buffer. In
                 * nojournal mode this race is harmless and we actually cannot
                 * call ext4_handle_dirty_xattr_block() with locked buffer as
                 * that function can call sync_dirty_buffer() so for that case
                 * we handle the dirtying after unlocking the buffer.
                 */
		if (ext4_handle_valid(handle))
			error