Re: [PATCH v5 27/28] ext4: xattr inode deduplication
From: Andreas Dilger
Date: Wed Jun 21 2017 - 13:42:26 EST
On Jun 20, 2017, at 3:49 AM, Tahsin Erdogan <tahsin@xxxxxxxxxx> wrote:
>
> Thanks Andreas for the feedback. Please see my responses below:
>
>> It would be preferable to allow a mount option like "no_mbcache" to disable
>> the use of shared xattrs. In the Lustre case at least, there will never be
>> shared large xattrs, and we've had a bunch of performance issues with mbcache
>> due to lock contention among many server threads doing concurrent lookups and
>> inserting many thousands of unique entries into the cache.
>
> I have put nombcache mount option in a separate patch ("[PATCH 32/32]
> ext4: add nombcache mount option"). I have named it nombcache instead
> of no_mbcache to be consistent with other no* options. Let me know if
> you prefer no_mbcache as the option name.
Tashin, we are already using the "no_mbcache" option name, so would prefer
to keep that working. It would be OK to accept both option names to mean
the same thing, and only document the "nombcache" option.
>> This should follow the existing convention of always using s_csum_seed to seed
>> the checksum, and change ext4_fill_super() to initialize s_csum_seed to ~0 if
>> ext4_has_metadata_csum() is false, or always use the same value regardless of
>> whether ext4_has_metadata_csum() is set or not.
>
> Done.
>
>> If it really necessary to have more than 2^32 references on a single shared
>> inode then it would be better to avoid the re-use of i_mtime, which breaks
>> the backref for unshared xattrs, and using i_size isn't enough of a guarantee
>> that this is the correct parent inode in case of on-disk corruption.
>
> I have now moved the lower 32bits of ref count from i_mtime to l_i_version.
>
>> Should this be contingent on ext4_has_metadata_csum() feature being enabled, or
>> alternately check if EXT4_XATTR_INODE_GET_PARENT() and i_generation match before
>> returning an error. This will allow a smooth transition from existing filesystems
>> that do not store the hash, but have only a single-use xattr inode with a parent
>> backref.
>
> I updated hash validation to fallback to parent backref check for
> backward compatibility.
Great, thanks.
>>> + /* Indirection block. */
>>> + blocks += 1;
>>
>> Strictly speaking, this is only needed "if (blocks > EXT4_NDIR_BLOCKS)".
>
> Ack. I didn't think it was worth going through exact calculation in
> this case, let me know if you see value in doing that.
> I also updated the comment to mention extents.
This one credit isn't a huge deal. In general, the number of credits reserved
can affect performance if they get too large, especially if there are a large
number of threads active, since this will cause premature journal flushing and
reduce the number of shared blocks written in the same transaction.
>>> + /* We may need to clone the existing xattr block in which case we need
>>> + * to increment ref counts for existing ea_inodes referenced by it.
>>> + */
>>
>> Just to clarify here, in the case of cloning an existing xattr block, are the
>> refcounts being _incremented_ or _decremented_ on the existing ea_inodes? I'm
>> trying to figure out if we really need to have credits for both old and new
>> xattr inodes, as well as these additional credits. Since this is reserving
>> about 110 blocks for every setxattr, this can add significant pressure on the
>> journal if there are lots of threads creating files and/or setting xattrs.
>
> Cloning causes incrementing xattr inode references.
>
>>> +ext4_xattr_inode_cache_find(struct inode *inode, const void *value,
>>> + size_t value_len, u32 hash)
>>> {
>>> + struct inode *ea_inode;
>>> + struct mb_cache_entry *ce;
>>> + struct mb_cache *ea_inode_cache = EA_INODE_CACHE(inode);
>>> + void *ea_data = NULL;
>>> int err;
>>
>> This function should just return NULL if ea_inode_cache is NULL (e.g. in
>> the case of "no_mbcache" mount option).
>
> Done in later patch ("[PATCH 32/32] ext4: add nombcache mount option")
>
>> Should skip mb_cache if EA_INODE_CACHE(inode) is NULL, or have a wrapper
>> like ext4_xattr_inode_cache_insert() to match ext4_xattr_inode_cache_find()
>> that does the same.
>
> Added skip in patch ("[PATCH 32/32] ext4: add nombcache mount option")
Thanks, I'm just going to go through those patches.
Cheers, Andreas
> On Tue, Jun 20, 2017 at 2:07 AM, Tahsin Erdogan <tahsin@xxxxxxxxxx> wrote:
>> Ext4 now supports xattr values that are up to 64k in size (vfs limit).
>> Large xattr values are stored in external inodes each one holding a
>> single value. Once written the data blocks of these inodes are immutable.
>>
>> The real world use cases are expected to have a lot of value duplication
>> such as inherited acls etc. To reduce data duplication on disk, this patch
>> implements a deduplicator that allows sharing of xattr inodes.
>>
>> The deduplication is based on an in-memory hash lookup that is a best
>> effort sharing scheme. When a xattr inode is read from disk (i.e.
>> getxattr() call), its crc32c hash is added to a hash table. Before
>> creating a new xattr inode for a value being set, the hash table is
>> checked to see if an existing inode holds an identical value. If such an
>> inode is found, the ref count on that inode is incremented. On value
>> removal the ref count is decremented and if it reaches zero the inode is
>> deleted.
>>
>> The quota charging for such inodes is manually managed. Every reference
>> holder is charged the full size as if there was no sharing happening.
>> This is consistent with how xattr blocks are also charged.
>>
>> Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
>> ---
>> v5:
>> - made ext4_meta_trans_blocks() static again since there are no
>> remaining users outside of inode.c
>> - initialize sbi->s_csum_seed when ea_inode feature is enabled
>> - use l_i_version to hold lower 32 bits of the xattr ref count.
>> This avoids clashes with old implementations which use i_mtime.
>> Since l_i_version is not available in HURD_COMPAT mode, fail mount
>> request when both ea_inode feature and HURD_COMPAT are set.
>> - when hash validation fails, fall back to old implementation
>> which has a backref to parent.
>> - fixed checkpatch.pl warning about using unsigned alone
>>
>> v4:
>> - eliminated xattr entry in the xattr inode to avoid complexity and
>> recursion in xattr update path. Now the ref count and hash are stored
>> in i_[c/m/a]time.tv_sec fields.
>> - some clean up in ext4_xattr_set_entry() to reduce code duplication and
>> complexity
>>
>> v3:
>> - use s_csum_seed for hash calculations when available
>> - return error on stored vs calculated hash mismatch
>>
>> v2:
>> - make dependency on crc32c dynamic
>> - update ext4_has_metadata_csum() and ext4_has_group_desc_csum() so that
>> they do not misinterpret existence of EXT4_SB(sb)->s_chksum_driver
>>
>> fs/ext4/acl.c | 5 +-
>> fs/ext4/ext4.h | 23 +-
>> fs/ext4/inode.c | 13 +-
>> fs/ext4/super.c | 37 +-
>> fs/ext4/xattr.c | 1038 +++++++++++++++++++++++++++++++++++++++++--------------
>> fs/ext4/xattr.h | 17 +-
>> fs/mbcache.c | 9 +-
>> 7 files changed, 848 insertions(+), 294 deletions(-)
>>
>> diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
>> index 74f7ac539e00..8db03e5c78bc 100644
>> --- a/fs/ext4/acl.c
>> +++ b/fs/ext4/acl.c
>> @@ -238,7 +238,10 @@ ext4_set_acl(struct inode *inode, struct posix_acl *acl, int type)
>> if (error)
>> return error;
>> retry:
>> - credits = ext4_xattr_set_credits(inode, acl_size);
>> + error = ext4_xattr_set_credits(inode, acl_size, &credits);
>> + if (error)
>> + return error;
>> +
>> handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
>> if (IS_ERR(handle))
>> return PTR_ERR(handle);
>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index d79d8d7bee88..59e9488c4876 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -1517,6 +1517,7 @@ struct ext4_sb_info {
>> long s_es_nr_inode;
>> struct ext4_es_stats s_es_stats;
>> struct mb_cache *s_mb_cache;
>> + struct mb_cache *s_ea_inode_cache;
>> spinlock_t s_es_lock ____cacheline_aligned_in_smp;
>>
>> /* Ratelimit ext4 messages. */
>> @@ -2099,7 +2100,11 @@ static inline struct ext4_inode *ext4_raw_inode(struct ext4_iloc *iloc)
>> return (struct ext4_inode *) (iloc->bh->b_data + iloc->offset);
>> }
>>
>> -#define ext4_is_quota_file(inode) IS_NOQUOTA(inode)
>> +static inline bool ext4_is_quota_file(struct inode *inode)
>> +{
>> + return IS_NOQUOTA(inode) &&
>> + !(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL);
>> +}
>>
>> /*
>> * This structure is stuffed into the struct file's private_data field
>> @@ -2482,7 +2487,6 @@ extern int ext4_truncate_restart_trans(handle_t *, struct inode *, int nblocks);
>> extern void ext4_set_inode_flags(struct inode *);
>> extern int ext4_alloc_da_blocks(struct inode *inode);
>> extern void ext4_set_aops(struct inode *inode);
>> -extern int ext4_meta_trans_blocks(struct inode *, int nrblocks, int chunk);
>> extern int ext4_writepage_trans_blocks(struct inode *);
>> extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
>> extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
>> @@ -2709,19 +2713,20 @@ extern void ext4_group_desc_csum_set(struct super_block *sb, __u32 group,
>> extern int ext4_register_li_request(struct super_block *sb,
>> ext4_group_t first_not_zeroed);
>>
>> -static inline int ext4_has_group_desc_csum(struct super_block *sb)
>> -{
>> - return ext4_has_feature_gdt_csum(sb) ||
>> - EXT4_SB(sb)->s_chksum_driver != NULL;
>> -}
>> -
>> static inline int ext4_has_metadata_csum(struct super_block *sb)
>> {
>> WARN_ON_ONCE(ext4_has_feature_metadata_csum(sb) &&
>> !EXT4_SB(sb)->s_chksum_driver);
>>
>> - return (EXT4_SB(sb)->s_chksum_driver != NULL);
>> + return ext4_has_feature_metadata_csum(sb) &&
>> + (EXT4_SB(sb)->s_chksum_driver != NULL);
>> }
>> +
>> +static inline int ext4_has_group_desc_csum(struct super_block *sb)
>> +{
>> + return ext4_has_feature_gdt_csum(sb) || ext4_has_metadata_csum(sb);
>> +}
>> +
>> static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)
>> {
>> return ((ext4_fsblk_t)le32_to_cpu(es->s_blocks_count_hi) << 32) |
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index cd007f9757d1..ea95bd9eab81 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -139,6 +139,8 @@ static void ext4_invalidatepage(struct page *page, unsigned int offset,
>> unsigned int length);
>> static int __ext4_journalled_writepage(struct page *page, unsigned int len);
>> static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
>> +static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
>> + int pextents);
>>
>> /*
>> * Test whether an inode is a fast symlink.
>> @@ -4843,8 +4845,15 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
>> }
>> brelse(iloc.bh);
>> ext4_set_inode_flags(inode);
>> - if (ei->i_flags & EXT4_EA_INODE_FL)
>> +
>> + if (ei->i_flags & EXT4_EA_INODE_FL) {
>> ext4_xattr_inode_set_class(inode);
>> +
>> + inode_lock(inode);
>> + inode->i_flags |= S_NOQUOTA;
>> + inode_unlock(inode);
>> + }
>> +
>> unlock_new_inode(inode);
>> return inode;
>>
>> @@ -5503,7 +5512,7 @@ static int ext4_index_trans_blocks(struct inode *inode, int lblocks,
>> *
>> * Also account for superblock, inode, quota and xattr blocks
>> */
>> -int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
>> +static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
>> int pextents)
>> {
>> ext4_group_t groups, ngroups = ext4_get_groups_count(inode->i_sb);
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index b02a23ec92ca..2bfacd737bb6 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -927,6 +927,10 @@ static void ext4_put_super(struct super_block *sb)
>> invalidate_bdev(sbi->journal_bdev);
>> ext4_blkdev_remove(sbi);
>> }
>> + if (sbi->s_ea_inode_cache) {
>> + ext4_xattr_destroy_cache(sbi->s_ea_inode_cache);
>> + sbi->s_ea_inode_cache = NULL;
>> + }
>> if (sbi->s_mb_cache) {
>> ext4_xattr_destroy_cache(sbi->s_mb_cache);
>> sbi->s_mb_cache = NULL;
>> @@ -1178,7 +1182,10 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
>> if (res)
>> return res;
>> retry:
>> - credits = ext4_xattr_set_credits(inode, len);
>> + res = ext4_xattr_set_credits(inode, len, &credits);
>> + if (res)
>> + return res;
>> +
>> handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
>> if (IS_ERR(handle))
>> return PTR_ERR(handle);
>> @@ -3445,7 +3452,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>> }
>>
>> /* Load the checksum driver */
>> - if (ext4_has_feature_metadata_csum(sb)) {
>> + if (ext4_has_feature_metadata_csum(sb) ||
>> + ext4_has_feature_ea_inode(sb)) {
>> sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
>> if (IS_ERR(sbi->s_chksum_driver)) {
>> ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
>> @@ -3467,7 +3475,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>> /* Precompute checksum seed for all metadata */
>> if (ext4_has_feature_csum_seed(sb))
>> sbi->s_csum_seed = le32_to_cpu(es->s_checksum_seed);
>> - else if (ext4_has_metadata_csum(sb))
>> + else if (ext4_has_metadata_csum(sb) || ext4_has_feature_ea_inode(sb))
>> sbi->s_csum_seed = ext4_chksum(sbi, ~0, es->s_uuid,
>> sizeof(es->s_uuid));
>>
>> @@ -3597,6 +3605,16 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>> "The Hurd can't support 64-bit file systems");
>> goto failed_mount;
>> }
>> +
>> + /*
>> + * ea_inode feature uses l_i_version field which is not
>> + * available in HURD_COMPAT mode.
>> + */
>> + if (ext4_has_feature_ea_inode(sb)) {
>> + ext4_msg(sb, KERN_ERR,
>> + "ea_inode feature is not supported for Hurd");
>> + goto failed_mount;
>> + }
>> }
>>
>> if (IS_EXT2_SB(sb)) {
>> @@ -4067,6 +4085,15 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>> goto failed_mount_wq;
>> }
>>
>> + if (ext4_has_feature_ea_inode(sb)) {
>> + sbi->s_ea_inode_cache = ext4_xattr_create_cache();
>> + if (!sbi->s_ea_inode_cache) {
>> + ext4_msg(sb, KERN_ERR,
>> + "Failed to create an s_ea_inode_cache");
>> + goto failed_mount_wq;
>> + }
>> + }
>> +
>> if ((DUMMY_ENCRYPTION_ENABLED(sbi) || ext4_has_feature_encrypt(sb)) &&
>> (blocksize != PAGE_SIZE)) {
>> ext4_msg(sb, KERN_ERR,
>> @@ -4296,6 +4323,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>> if (EXT4_SB(sb)->rsv_conversion_wq)
>> destroy_workqueue(EXT4_SB(sb)->rsv_conversion_wq);
>> failed_mount_wq:
>> + if (sbi->s_ea_inode_cache) {
>> + ext4_xattr_destroy_cache(sbi->s_ea_inode_cache);
>> + sbi->s_ea_inode_cache = NULL;
>> + }
>> if (sbi->s_mb_cache) {
>> ext4_xattr_destroy_cache(sbi->s_mb_cache);
>> sbi->s_mb_cache = NULL;
>> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
>> index 0484df8dadd1..d7e60358ec91 100644
>> --- a/fs/ext4/xattr.c
>> +++ b/fs/ext4/xattr.c
>> @@ -108,6 +108,9 @@ const struct xattr_handler *ext4_xattr_handlers[] = {
>> #define EXT4_GET_MB_CACHE(inode) (((struct ext4_sb_info *) \
>> inode->i_sb->s_fs_info)->s_mb_cache)
>>
>> +#define EA_INODE_CACHE(inode) (((struct ext4_sb_info *) \
>> + inode->i_sb->s_fs_info)->s_ea_inode_cache)
>> +
>> static int
>> ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
>> struct inode *inode);
>> @@ -280,15 +283,44 @@ ext4_xattr_find_entry(struct ext4_xattr_entry **pentry, int name_index,
>> return cmp ? -ENODATA : 0;
>> }
>>
>> +static u32
>> +ext4_xattr_inode_hash(struct ext4_sb_info *sbi, const void *buffer, size_t size)
>> +{
>> + return ext4_chksum(sbi, sbi->s_csum_seed, buffer, size);
>> +}
>> +
>> +static u64 ext4_xattr_inode_get_ref(struct inode *ea_inode)
>> +{
>> + return ((u64)ea_inode->i_ctime.tv_sec << 32) |
>> + ((u32)ea_inode->i_version);
>> +}
>> +
>> +static void ext4_xattr_inode_set_ref(struct inode *ea_inode, u64 ref_count)
>> +{
>> + ea_inode->i_ctime.tv_sec = (u32)(ref_count >> 32);
>> + ea_inode->i_version = (u32)ref_count;
>> +}
>> +
>> +static u32 ext4_xattr_inode_get_hash(struct inode *ea_inode)
>> +{
>> + return (u32)ea_inode->i_atime.tv_sec;
>> +}
>> +
>> +static void ext4_xattr_inode_set_hash(struct inode *ea_inode, u32 hash)
>> +{
>> + ea_inode->i_atime.tv_sec = hash;
>> +}
>> +
>> /*
>> * Read the EA value from an inode.
>> */
>> static int ext4_xattr_inode_read(struct inode *ea_inode, void *buf, size_t size)
>> {
>> unsigned long block = 0;
>> - struct buffer_head *bh = NULL;
>> + struct buffer_head *bh;
>> int blocksize = ea_inode->i_sb->s_blocksize;
>> size_t csize, copied = 0;
>> + void *copy_pos = buf;
>>
>> while (copied < size) {
>> csize = (size - copied) > blocksize ? blocksize : size - copied;
>> @@ -298,10 +330,10 @@ static int ext4_xattr_inode_read(struct inode *ea_inode, void *buf, size_t size)
>> if (!bh)
>> return -EFSCORRUPTED;
>>
>> - memcpy(buf, bh->b_data, csize);
>> + memcpy(copy_pos, bh->b_data, csize);
>> brelse(bh);
>>
>> - buf += csize;
>> + copy_pos += csize;
>> block += 1;
>> copied += csize;
>> }
>> @@ -317,29 +349,24 @@ static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino,
>> inode = ext4_iget(parent->i_sb, ea_ino);
>> if (IS_ERR(inode)) {
>> err = PTR_ERR(inode);
>> - ext4_error(parent->i_sb, "error while reading EA inode %lu "
>> - "err=%d", ea_ino, err);
>> + ext4_error(parent->i_sb,
>> + "error while reading EA inode %lu err=%d", ea_ino,
>> + err);
>> return err;
>> }
>>
>> if (is_bad_inode(inode)) {
>> - ext4_error(parent->i_sb, "error while reading EA inode %lu "
>> - "is_bad_inode", ea_ino);
>> + ext4_error(parent->i_sb,
>> + "error while reading EA inode %lu is_bad_inode",
>> + ea_ino);
>> err = -EIO;
>> goto error;
>> }
>>
>> - if (EXT4_XATTR_INODE_GET_PARENT(inode) != parent->i_ino ||
>> - inode->i_generation != parent->i_generation) {
>> - ext4_error(parent->i_sb, "Backpointer from EA inode %lu "
>> - "to parent is invalid.", ea_ino);
>> - err = -EINVAL;
>> - goto error;
>> - }
>> -
>> if (!(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) {
>> - ext4_error(parent->i_sb, "EA inode %lu does not have "
>> - "EXT4_EA_INODE_FL flag set.\n", ea_ino);
>> + ext4_error(parent->i_sb,
>> + "EA inode %lu does not have EXT4_EA_INODE_FL flag",
>> + ea_ino);
>> err = -EINVAL;
>> goto error;
>> }
>> @@ -351,6 +378,20 @@ static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino,
>> return err;
>> }
>>
>> +static int
>> +ext4_xattr_inode_verify_hash(struct inode *ea_inode, void *buffer, size_t size)
>> +{
>> + u32 hash;
>> +
>> + /* Verify stored hash matches calculated hash. */
>> + hash = ext4_xattr_inode_hash(EXT4_SB(ea_inode->i_sb), buffer, size);
>> + if (hash != ext4_xattr_inode_get_hash(ea_inode))
>> + return -EFSCORRUPTED;
>> + return 0;
>> +}
>> +
>> +#define EXT4_XATTR_INODE_GET_PARENT(inode) ((__u32)(inode)->i_mtime.tv_sec)
>> +
>> /*
>> * Read the value from the EA inode.
>> */
>> @@ -358,17 +399,53 @@ static int
>> ext4_xattr_inode_get(struct inode *inode, unsigned long ea_ino, void *buffer,
>> size_t size)
>> {
>> + struct mb_cache *ea_inode_cache = EA_INODE_CACHE(inode);
>> struct inode *ea_inode;
>> - int ret;
>> + int err;
>>
>> - ret = ext4_xattr_inode_iget(inode, ea_ino, &ea_inode);
>> - if (ret)
>> - return ret;
>> + err = ext4_xattr_inode_iget(inode, ea_ino, &ea_inode);
>> + if (err) {
>> + ea_inode = NULL;
>> + goto out;
>> + }
>>
>> - ret = ext4_xattr_inode_read(ea_inode, buffer, size);
>> - iput(ea_inode);
>> + if (i_size_read(ea_inode) != size) {
>> + ext4_warning_inode(ea_inode,
>> + "ea_inode file size=%llu entry size=%zu",
>> + i_size_read(ea_inode), size);
>> + err = -EFSCORRUPTED;
>> + goto out;
>> + }
>>
>> - return ret;
>> + err = ext4_xattr_inode_read(ea_inode, buffer, size);
>> + if (err)
>> + goto out;
>> +
>> + err = ext4_xattr_inode_verify_hash(ea_inode, buffer, size);
>> + /*
>> + * Compatibility check for old Lustre ea_inode implementation. Old
>> + * version does not have hash validation, but it has a backpointer
>> + * from ea_inode to the parent inode.
>> + */
>> + if (err == -EFSCORRUPTED) {
>> + if (EXT4_XATTR_INODE_GET_PARENT(ea_inode) != inode->i_ino ||
>> + ea_inode->i_generation != inode->i_generation) {
>> + ext4_warning_inode(ea_inode,
>> + "EA inode hash validation failed");
>> + goto out;
>> + }
>> + /* Do not add ea_inode to the cache. */
>> + ea_inode_cache = NULL;
>> + } else if (err)
>> + goto out;
>> +
>> + if (ea_inode_cache)
>> + mb_cache_entry_create(ea_inode_cache, GFP_NOFS,
>> + ext4_xattr_inode_get_hash(ea_inode),
>> + ea_inode->i_ino, true /* reusable */);
>> +out:
>> + iput(ea_inode);
>> + return err;
>> }
>>
>> static int
>> @@ -657,6 +734,101 @@ static void ext4_xattr_update_super_block(handle_t *handle,
>> }
>> }
>>
>> +static inline size_t round_up_cluster(struct inode *inode, size_t length)
>> +{
>> + struct super_block *sb = inode->i_sb;
>> + size_t cluster_size = 1 << (EXT4_SB(sb)->s_cluster_bits +
>> + inode->i_blkbits);
>> + size_t mask = ~(cluster_size - 1);
>> +
>> + return (length + cluster_size - 1) & mask;
>> +}
>> +
>> +static int ext4_xattr_inode_alloc_quota(struct inode *inode, size_t len)
>> +{
>> + int err;
>> +
>> + err = dquot_alloc_inode(inode);
>> + if (err)
>> + return err;
>> + err = dquot_alloc_space_nodirty(inode, round_up_cluster(inode, len));
>> + if (err)
>> + dquot_free_inode(inode);
>> + return err;
>> +}
>> +
>> +static void ext4_xattr_inode_free_quota(struct inode *inode, size_t len)
>> +{
>> + dquot_free_space_nodirty(inode, round_up_cluster(inode, len));
>> + dquot_free_inode(inode);
>> +}
>> +
>> +static int __ext4_xattr_set_credits(struct super_block *sb,
>> + struct buffer_head *block_bh,
>> + size_t value_len)
>> +{
>> + int credits;
>> + int blocks;
>> +
>> + /*
>> + * 1) Owner inode update
>> + * 2) Ref count update on old xattr block
>> + * 3) new xattr block
>> + * 4) block bitmap update for new xattr block
>> + * 5) group descriptor for new xattr block
>> + */
>> + credits = 5;
>> +
>> + /* We are done if ea_inode feature is not enabled. */
>> + if (!ext4_has_feature_ea_inode(sb))
>> + return credits;
>> +
>> + /* New ea_inode, inode map, block bitmap, group descriptor. */
>> + credits += 4;
>> +
>> + /* Data blocks. */
>> + blocks = (value_len + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
>> +
>> + /* Indirection block or one level of extent tree. */
>> + blocks += 1;
>> +
>> + /* Block bitmap and group descriptor updates for each block. */
>> + credits += blocks * 2;
>> +
>> + /* Blocks themselves. */
>> + credits += blocks;
>> +
>> + /* Dereference ea_inode holding old xattr value.
>> + * Old ea_inode, inode map, block bitmap, group descriptor.
>> + */
>> + credits += 4;
>> +
>> + /* Data blocks for old ea_inode. */
>> + blocks = XATTR_SIZE_MAX >> sb->s_blocksize_bits;
>> +
>> + /* Indirection block or one level of extent tree for old ea_inode. */
>> + blocks += 1;
>> +
>> + /* Block bitmap and group descriptor updates for each block. */
>> + credits += blocks * 2;
>> +
>> + /* Quota updates. */
>> + credits += EXT4_MAXQUOTAS_TRANS_BLOCKS(sb);
>> +
>> + /* We may need to clone the existing xattr block in which case we need
>> + * to increment ref counts for existing ea_inodes referenced by it.
>> + */
>> + if (block_bh) {
>> + struct ext4_xattr_entry *entry = BFIRST(block_bh);
>> +
>> + for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry))
>> + if (entry->e_value_inum)
>> + /* Ref count update on ea_inode. */
>> + credits += 1;
>> + }
>> + return credits;
>> +}
>> +
>> static int ext4_xattr_ensure_credits(handle_t *handle, struct inode *inode,
>> int credits, struct buffer_head *bh,
>> bool dirty, bool block_csum)
>> @@ -706,12 +878,140 @@ static int ext4_xattr_ensure_credits(handle_t *handle, struct inode *inode,
>> return 0;
>> }
>>
>> +static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode,
>> + int ref_change)
>> +{
>> + struct mb_cache *ea_inode_cache = EA_INODE_CACHE(ea_inode);
>> + struct ext4_iloc iloc;
>> + s64 ref_count;
>> + u32 hash;
>> + int ret;
>> +
>> + inode_lock(ea_inode);
>> +
>> + ret = ext4_reserve_inode_write(handle, ea_inode, &iloc);
>> + if (ret) {
>> + iloc.bh = NULL;
>> + goto out;
>> + }
>> +
>> + ref_count = ext4_xattr_inode_get_ref(ea_inode);
>> + ref_count += ref_change;
>> + ext4_xattr_inode_set_ref(ea_inode, ref_count);
>> +
>> + if (ref_change > 0) {
>> + WARN_ONCE(ref_count <= 0, "EA inode %lu ref_count=%lld",
>> + ea_inode->i_ino, ref_count);
>> +
>> + if (ref_count == 1) {
>> + WARN_ONCE(ea_inode->i_nlink, "EA inode %lu i_nlink=%u",
>> + ea_inode->i_ino, ea_inode->i_nlink);
>> +
>> + set_nlink(ea_inode, 1);
>> + ext4_orphan_del(handle, ea_inode);
>> +
>> + hash = ext4_xattr_inode_get_hash(ea_inode);
>> + mb_cache_entry_create(ea_inode_cache, GFP_NOFS, hash,
>> + ea_inode->i_ino,
>> + true /* reusable */);
>> + }
>> + } else {
>> + WARN_ONCE(ref_count < 0, "EA inode %lu ref_count=%lld",
>> + ea_inode->i_ino, ref_count);
>> +
>> + if (ref_count == 0) {
>> + WARN_ONCE(ea_inode->i_nlink != 1,
>> + "EA inode %lu i_nlink=%u",
>> + ea_inode->i_ino, ea_inode->i_nlink);
>> +
>> + clear_nlink(ea_inode);
>> + ext4_orphan_add(handle, ea_inode);
>> +
>> + hash = ext4_xattr_inode_get_hash(ea_inode);
>> + mb_cache_entry_delete(ea_inode_cache, hash,
>> + ea_inode->i_ino);
>> + }
>> + }
>> +
>> + ret = ext4_mark_iloc_dirty(handle, ea_inode, &iloc);
>> + iloc.bh = NULL;
>> + if (ret)
>> + ext4_warning_inode(ea_inode,
>> + "ext4_mark_iloc_dirty() failed ret=%d", ret);
>> +out:
>> + brelse(iloc.bh);
>> + inode_unlock(ea_inode);
>> + return ret;
>> +}
>> +
>> +static int ext4_xattr_inode_inc_ref(handle_t *handle, struct inode *ea_inode)
>> +{
>> + return ext4_xattr_inode_update_ref(handle, ea_inode, 1);
>> +}
>> +
>> +static int ext4_xattr_inode_dec_ref(handle_t *handle, struct inode *ea_inode)
>> +{
>> + return ext4_xattr_inode_update_ref(handle, ea_inode, -1);
>> +}
>> +
>> +static int ext4_xattr_inode_inc_ref_all(handle_t *handle, struct inode *parent,
>> + struct ext4_xattr_entry *first)
>> +{
>> + struct inode *ea_inode;
>> + struct ext4_xattr_entry *entry;
>> + struct ext4_xattr_entry *failed_entry;
>> + unsigned int ea_ino;
>> + int err, saved_err;
>> +
>> + for (entry = first; !IS_LAST_ENTRY(entry);
>> + entry = EXT4_XATTR_NEXT(entry)) {
>> + if (!entry->e_value_inum)
>> + continue;
>> + ea_ino = le32_to_cpu(entry->e_value_inum);
>> + err = ext4_xattr_inode_iget(parent, ea_ino, &ea_inode);
>> + if (err)
>> + goto cleanup;
>> + err = ext4_xattr_inode_inc_ref(handle, ea_inode);
>> + if (err) {
>> + ext4_warning_inode(ea_inode, "inc ref error %d", err);
>> + iput(ea_inode);
>> + goto cleanup;
>> + }
>> + iput(ea_inode);
>> + }
>> + return 0;
>> +
>> +cleanup:
>> + saved_err = err;
>> + failed_entry = entry;
>> +
>> + for (entry = first; entry != failed_entry;
>> + entry = EXT4_XATTR_NEXT(entry)) {
>> + if (!entry->e_value_inum)
>> + continue;
>> + ea_ino = le32_to_cpu(entry->e_value_inum);
>> + err = ext4_xattr_inode_iget(parent, ea_ino, &ea_inode);
>> + if (err) {
>> + ext4_warning(parent->i_sb,
>> + "cleanup ea_ino %u iget error %d", ea_ino,
>> + err);
>> + continue;
>> + }
>> + err = ext4_xattr_inode_dec_ref(handle, ea_inode);
>> + if (err)
>> + ext4_warning_inode(ea_inode, "cleanup dec ref error %d",
>> + err);
>> + iput(ea_inode);
>> + }
>> + return saved_err;
>> +}
>> +
>> static void
>> -ext4_xattr_inode_remove_all(handle_t *handle, struct inode *parent,
>> - struct buffer_head *bh,
>> - struct ext4_xattr_entry *first, bool block_csum,
>> - struct ext4_xattr_inode_array **ea_inode_array,
>> - int extra_credits)
>> +ext4_xattr_inode_dec_ref_all(handle_t *handle, struct inode *parent,
>> + struct buffer_head *bh,
>> + struct ext4_xattr_entry *first, bool block_csum,
>> + struct ext4_xattr_inode_array **ea_inode_array,
>> + int extra_credits, bool skip_quota)
>> {
>> struct inode *ea_inode;
>> struct ext4_xattr_entry *entry;
>> @@ -748,10 +1048,16 @@ ext4_xattr_inode_remove_all(handle_t *handle, struct inode *parent,
>> continue;
>> }
>>
>> - inode_lock(ea_inode);
>> - clear_nlink(ea_inode);
>> - ext4_orphan_add(handle, ea_inode);
>> - inode_unlock(ea_inode);
>> + err = ext4_xattr_inode_dec_ref(handle, ea_inode);
>> + if (err) {
>> + ext4_warning_inode(ea_inode, "ea_inode dec ref err=%d",
>> + err);
>> + continue;
>> + }
>> +
>> + if (!skip_quota)
>> + ext4_xattr_inode_free_quota(parent,
>> + le32_to_cpu(entry->e_value_size));
>>
>> /*
>> * Forget about ea_inode within the same transaction that
>> @@ -785,7 +1091,9 @@ ext4_xattr_inode_remove_all(handle_t *handle, struct inode *parent,
>> */
>> static void
>> ext4_xattr_release_block(handle_t *handle, struct inode *inode,
>> - struct buffer_head *bh)
>> + struct buffer_head *bh,
>> + struct ext4_xattr_inode_array **ea_inode_array,
>> + int extra_credits)
>> {
>> struct mb_cache *ext4_mb_cache = EXT4_GET_MB_CACHE(inode);
>> u32 hash, ref;
>> @@ -808,6 +1116,14 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
>> mb_cache_entry_delete(ext4_mb_cache, hash, bh->b_blocknr);
>> get_bh(bh);
>> unlock_buffer(bh);
>> +
>> + if (ext4_has_feature_ea_inode(inode->i_sb))
>> + ext4_xattr_inode_dec_ref_all(handle, inode, bh,
>> + BFIRST(bh),
>> + true /* block_csum */,
>> + ea_inode_array,
>> + extra_credits,
>> + true /* skip_quota */);
>> ext4_free_blocks(handle, inode, bh, 0, 1,
>> EXT4_FREE_BLOCKS_METADATA |
>> EXT4_FREE_BLOCKS_FORGET);
>> @@ -879,8 +1195,8 @@ static int ext4_xattr_inode_write(handle_t *handle, struct inode *ea_inode,
>> {
>> struct buffer_head *bh = NULL;
>> unsigned long block = 0;
>> - unsigned blocksize = ea_inode->i_sb->s_blocksize;
>> - unsigned max_blocks = (bufsize + blocksize - 1) >> ea_inode->i_blkbits;
>> + int blocksize = ea_inode->i_sb->s_blocksize;
>> + int max_blocks = (bufsize + blocksize - 1) >> ea_inode->i_blkbits;
>> int csize, wsize = 0;
>> int ret = 0;
>> int retries = 0;
>> @@ -948,7 +1264,7 @@ static int ext4_xattr_inode_write(handle_t *handle, struct inode *ea_inode,
>> * Create an inode to store the value of a large EA.
>> */
>> static struct inode *ext4_xattr_inode_create(handle_t *handle,
>> - struct inode *inode)
>> + struct inode *inode, u32 hash)
>> {
>> struct inode *ea_inode = NULL;
>> uid_t owner[2] = { i_uid_read(inode), i_gid_read(inode) };
>> @@ -966,67 +1282,115 @@ static struct inode *ext4_xattr_inode_create(handle_t *handle,
>> ea_inode->i_fop = &ext4_file_operations;
>> ext4_set_aops(ea_inode);
>> ext4_xattr_inode_set_class(ea_inode);
>> - ea_inode->i_generation = inode->i_generation;
>> - EXT4_I(ea_inode)->i_flags |= EXT4_EA_INODE_FL;
>> -
>> - /*
>> - * A back-pointer from EA inode to parent inode will be useful
>> - * for e2fsck.
>> - */
>> - EXT4_XATTR_INODE_SET_PARENT(ea_inode, inode->i_ino);
>> unlock_new_inode(ea_inode);
>> - err = ext4_inode_attach_jinode(ea_inode);
>> + ext4_xattr_inode_set_ref(ea_inode, 1);
>> + ext4_xattr_inode_set_hash(ea_inode, hash);
>> + err = ext4_mark_inode_dirty(handle, ea_inode);
>> + if (!err)
>> + err = ext4_inode_attach_jinode(ea_inode);
>> if (err) {
>> iput(ea_inode);
>> return ERR_PTR(err);
>> }
>> +
>> + /*
>> + * Xattr inodes are shared therefore quota charging is performed
>> + * at a higher level.
>> + */
>> + dquot_free_inode(ea_inode);
>> + dquot_drop(ea_inode);
>> + inode_lock(ea_inode);
>> + ea_inode->i_flags |= S_NOQUOTA;
>> + inode_unlock(ea_inode);
>> }
>>
>> return ea_inode;
>> }
>>
>> -/*
>> - * Unlink the inode storing the value of the EA.
>> - */
>> -int ext4_xattr_inode_unlink(struct inode *inode, unsigned long ea_ino)
>> +static struct inode *
>> +ext4_xattr_inode_cache_find(struct inode *inode, const void *value,
>> + size_t value_len, u32 hash)
>> {
>> - struct inode *ea_inode = NULL;
>> - int err;
>> + struct inode *ea_inode;
>> + struct mb_cache_entry *ce;
>> + struct mb_cache *ea_inode_cache = EA_INODE_CACHE(inode);
>> + void *ea_data;
>>
>> - err = ext4_xattr_inode_iget(inode, ea_ino, &ea_inode);
>> - if (err)
>> - return err;
>> + ce = mb_cache_entry_find_first(ea_inode_cache, hash);
>> + if (!ce)
>> + return NULL;
>>
>> - clear_nlink(ea_inode);
>> - iput(ea_inode);
>> + ea_data = ext4_kvmalloc(value_len, GFP_NOFS);
>> + if (!ea_data) {
>> + mb_cache_entry_put(ea_inode_cache, ce);
>> + return NULL;
>> + }
>>
>> - return 0;
>> + while (ce) {
>> + ea_inode = ext4_iget(inode->i_sb, ce->e_value);
>> + if (!IS_ERR(ea_inode) &&
>> + !is_bad_inode(ea_inode) &&
>> + (EXT4_I(ea_inode)->i_flags & EXT4_EA_INODE_FL) &&
>> + i_size_read(ea_inode) == value_len &&
>> + !ext4_xattr_inode_read(ea_inode, ea_data, value_len) &&
>> + !ext4_xattr_inode_verify_hash(ea_inode, ea_data,
>> + value_len) &&
>> + !memcmp(value, ea_data, value_len)) {
>> + mb_cache_entry_touch(ea_inode_cache, ce);
>> + mb_cache_entry_put(ea_inode_cache, ce);
>> + kvfree(ea_data);
>> + return ea_inode;
>> + }
>> +
>> + if (!IS_ERR(ea_inode))
>> + iput(ea_inode);
>> + ce = mb_cache_entry_find_next(ea_inode_cache, ce);
>> + }
>> + kvfree(ea_data);
>> + return NULL;
>> }
>>
>> /*
>> * Add value of the EA in an inode.
>> */
>> -static int ext4_xattr_inode_set(handle_t *handle, struct inode *inode,
>> - unsigned long *ea_ino, const void *value,
>> - size_t value_len)
>> +static int ext4_xattr_inode_lookup_create(handle_t *handle, struct inode *inode,
>> + const void *value, size_t value_len,
>> + struct inode **ret_inode)
>> {
>> struct inode *ea_inode;
>> + u32 hash;
>> int err;
>>
>> + hash = ext4_xattr_inode_hash(EXT4_SB(inode->i_sb), value, value_len);
>> + ea_inode = ext4_xattr_inode_cache_find(inode, value, value_len, hash);
>> + if (ea_inode) {
>> + err = ext4_xattr_inode_inc_ref(handle, ea_inode);
>> + if (err) {
>> + iput(ea_inode);
>> + return err;
>> + }
>> +
>> + *ret_inode = ea_inode;
>> + return 0;
>> + }
>> +
>> /* Create an inode for the EA value */
>> - ea_inode = ext4_xattr_inode_create(handle, inode);
>> + ea_inode = ext4_xattr_inode_create(handle, inode, hash);
>> if (IS_ERR(ea_inode))
>> return PTR_ERR(ea_inode);
>>
>> err = ext4_xattr_inode_write(handle, ea_inode, value, value_len);
>> - if (err)
>> - clear_nlink(ea_inode);
>> - else
>> - *ea_ino = ea_inode->i_ino;
>> + if (err) {
>> + ext4_xattr_inode_dec_ref(handle, ea_inode);
>> + iput(ea_inode);
>> + return err;
>> + }
>>
>> - iput(ea_inode);
>> + mb_cache_entry_create(EA_INODE_CACHE(inode), GFP_NOFS, hash,
>> + ea_inode->i_ino, true /* reusable */);
>>
>> - return err;
>> + *ret_inode = ea_inode;
>> + return 0;
>> }
>>
>> static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
>> @@ -1034,9 +1398,37 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
>> handle_t *handle, struct inode *inode)
>> {
>> struct ext4_xattr_entry *last;
>> - size_t free, min_offs = s->end - s->base, name_len = strlen(i->name);
>> + struct ext4_xattr_entry *here = s->here;
>> + size_t min_offs = s->end - s->base, name_len = strlen(i->name);
>> int in_inode = i->in_inode;
>> - int rc;
>> + struct inode *old_ea_inode = NULL;
>> + struct inode *new_ea_inode = NULL;
>> + size_t old_size, new_size;
>> + int ret;
>> +
>> + /* Space used by old and new values. */
>> + old_size = (!s->not_found && !here->e_value_inum) ?
>> + EXT4_XATTR_SIZE(le32_to_cpu(here->e_value_size)) : 0;
>> + new_size = (i->value && !in_inode) ? EXT4_XATTR_SIZE(i->value_len) : 0;
>> +
>> + /*
>> + * Optimization for the simple case when old and new values have the
>> + * same padded sizes. Not applicable if external inodes are involved.
>> + */
>> + if (new_size && new_size == old_size) {
>> + size_t offs = le16_to_cpu(here->e_value_offs);
>> + void *val = s->base + offs;
>> +
>> + here->e_value_size = cpu_to_le32(i->value_len);
>> + if (i->value == EXT4_ZERO_XATTR_VALUE) {
>> + memset(val, 0, new_size);
>> + } else {
>> + memcpy(val, i->value, i->value_len);
>> + /* Clear padding bytes. */
>> + memset(val + i->value_len, 0, new_size - i->value_len);
>> + }
>> + return 0;
>> + }
>>
>> /* Compute min_offs and last. */
>> last = s->first;
>> @@ -1047,122 +1439,148 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
>> min_offs = offs;
>> }
>> }
>> - free = min_offs - ((void *)last - s->base) - sizeof(__u32);
>> - if (!s->not_found) {
>> - if (!in_inode &&
>> - !s->here->e_value_inum && s->here->e_value_size) {
>> - size_t size = le32_to_cpu(s->here->e_value_size);
>> - free += EXT4_XATTR_SIZE(size);
>> - }
>> - free += EXT4_XATTR_LEN(name_len);
>> - }
>> +
>> + /* Check whether we have enough space. */
>> if (i->value) {
>> - size_t value_len = EXT4_XATTR_SIZE(i->value_len);
>> + size_t free;
>>
>> - if (in_inode)
>> - value_len = 0;
>> + free = min_offs - ((void *)last - s->base) - sizeof(__u32);
>> + if (!s->not_found)
>> + free += EXT4_XATTR_LEN(name_len) + old_size;
>>
>> - if (free < EXT4_XATTR_LEN(name_len) + value_len)
>> - return -ENOSPC;
>> + if (free < EXT4_XATTR_LEN(name_len) + new_size) {
>> + ret = -ENOSPC;
>> + goto out;
>> + }
>> }
>>
>> - if (i->value && s->not_found) {
>> - /* Insert the new name. */
>> - size_t size = EXT4_XATTR_LEN(name_len);
>> - size_t rest = (void *)last - (void *)s->here + sizeof(__u32);
>> - memmove((void *)s->here + size, s->here, rest);
>> - memset(s->here, 0, size);
>> - s->here->e_name_index = i->name_index;
>> - s->here->e_name_len = name_len;
>> - memcpy(s->here->e_name, i->name, name_len);
>> - } else {
>> - if (!s->here->e_value_inum && s->here->e_value_size &&
>> - s->here->e_value_offs > 0) {
>> - void *first_val = s->base + min_offs;
>> - size_t offs = le16_to_cpu(s->here->e_value_offs);
>> - void *val = s->base + offs;
>> - size_t size = EXT4_XATTR_SIZE(
>> - le32_to_cpu(s->here->e_value_size));
>> -
>> - if (i->value && size == EXT4_XATTR_SIZE(i->value_len)) {
>> - /* The old and the new value have the same
>> - size. Just replace. */
>> - s->here->e_value_size =
>> - cpu_to_le32(i->value_len);
>> - if (i->value == EXT4_ZERO_XATTR_VALUE) {
>> - memset(val, 0, size);
>> - } else {
>> - /* Clear pad bytes first. */
>> - memset(val + size - EXT4_XATTR_PAD, 0,
>> - EXT4_XATTR_PAD);
>> - memcpy(val, i->value, i->value_len);
>> - }
>> - return 0;
>> - }
>> + /*
>> + * Getting access to old and new ea inodes is subject to failures.
>> + * Finish that work before doing any modifications to the xattr data.
>> + */
>> + if (!s->not_found && here->e_value_inum) {
>> + ret = ext4_xattr_inode_iget(inode,
>> + le32_to_cpu(here->e_value_inum),
>> + &old_ea_inode);
>> + if (ret) {
>> + old_ea_inode = NULL;
>> + goto out;
>> + }
>> + }
>> + if (i->value && in_inode) {
>> + WARN_ON_ONCE(!i->value_len);
>>
>> - /* Remove the old value. */
>> - memmove(first_val + size, first_val, val - first_val);
>> - memset(first_val, 0, size);
>> - s->here->e_value_size = 0;
>> - s->here->e_value_offs = 0;
>> - min_offs += size;
>> -
>> - /* Adjust all value offsets. */
>> - last = s->first;
>> - while (!IS_LAST_ENTRY(last)) {
>> - size_t o = le16_to_cpu(last->e_value_offs);
>> - if (!last->e_value_inum &&
>> - last->e_value_size && o < offs)
>> - last->e_value_offs =
>> - cpu_to_le16(o + size);
>> - last = EXT4_XATTR_NEXT(last);
>> - }
>> + ret = ext4_xattr_inode_alloc_quota(inode, i->value_len);
>> + if (ret)
>> + goto out;
>> +
>> + ret = ext4_xattr_inode_lookup_create(handle, inode, i->value,
>> + i->value_len,
>> + &new_ea_inode);
>> + if (ret) {
>> + new_ea_inode = NULL;
>> + ext4_xattr_inode_free_quota(inode, i->value_len);
>> + goto out;
>> }
>> - if (s->here->e_value_inum) {
>> - ext4_xattr_inode_unlink(inode,
>> - le32_to_cpu(s->here->e_value_inum));
>> - s->here->e_value_inum = 0;
>> + }
>> +
>> + if (old_ea_inode) {
>> + /* We are ready to release ref count on the old_ea_inode. */
>> + ret = ext4_xattr_inode_dec_ref(handle, old_ea_inode);
>> + if (ret) {
>> + /* Release newly required ref count on new_ea_inode. */
>> + if (new_ea_inode) {
>> + int err;
>> +
>> + err = ext4_xattr_inode_dec_ref(handle,
>> + new_ea_inode);
>> + if (err)
>> + ext4_warning_inode(new_ea_inode,
>> + "dec ref new_ea_inode err=%d",
>> + err);
>> + ext4_xattr_inode_free_quota(inode,
>> + i->value_len);
>> + }
>> + goto out;
>> }
>> - if (!i->value) {
>> - /* Remove the old name. */
>> - size_t size = EXT4_XATTR_LEN(name_len);
>> - last = ENTRY((void *)last - size);
>> - memmove(s->here, (void *)s->here + size,
>> - (void *)last - (void *)s->here + sizeof(__u32));
>> - memset(last, 0, size);
>> +
>> + ext4_xattr_inode_free_quota(inode,
>> + le32_to_cpu(here->e_value_size));
>> + }
>> +
>> + /* No failures allowed past this point. */
>> +
>> + if (!s->not_found && here->e_value_offs) {
>> + /* Remove the old value. */
>> + void *first_val = s->base + min_offs;
>> + size_t offs = le16_to_cpu(here->e_value_offs);
>> + void *val = s->base + offs;
>> +
>> + memmove(first_val + old_size, first_val, val - first_val);
>> + memset(first_val, 0, old_size);
>> + min_offs += old_size;
>> +
>> + /* Adjust all value offsets. */
>> + last = s->first;
>> + while (!IS_LAST_ENTRY(last)) {
>> + size_t o = le16_to_cpu(last->e_value_offs);
>> +
>> + if (!last->e_value_inum &&
>> + last->e_value_size && o < offs)
>> + last->e_value_offs = cpu_to_le16(o + old_size);
>> + last = EXT4_XATTR_NEXT(last);
>> }
>> }
>>
>> + if (!i->value) {
>> + /* Remove old name. */
>> + size_t size = EXT4_XATTR_LEN(name_len);
>> +
>> + last = ENTRY((void *)last - size);
>> + memmove(here, (void *)here + size,
>> + (void *)last - (void *)here + sizeof(__u32));
>> + memset(last, 0, size);
>> + } else if (s->not_found) {
>> + /* Insert new name. */
>> + size_t size = EXT4_XATTR_LEN(name_len);
>> + size_t rest = (void *)last - (void *)here + sizeof(__u32);
>> +
>> + memmove((void *)here + size, here, rest);
>> + memset(here, 0, size);
>> + here->e_name_index = i->name_index;
>> + here->e_name_len = name_len;
>> + memcpy(here->e_name, i->name, name_len);
>> + } else {
>> + /* This is an update, reset value info. */
>> + here->e_value_inum = 0;
>> + here->e_value_offs = 0;
>> + here->e_value_size = 0;
>> + }
>> +
>> if (i->value) {
>> - /* Insert the new value. */
>> + /* Insert new value. */
>> if (in_inode) {
>> - unsigned long ea_ino =
>> - le32_to_cpu(s->here->e_value_inum);
>> - rc = ext4_xattr_inode_set(handle, inode, &ea_ino,
>> - i->value, i->value_len);
>> - if (rc)
>> - goto out;
>> - s->here->e_value_inum = cpu_to_le32(ea_ino);
>> - s->here->e_value_offs = 0;
>> + here->e_value_inum = cpu_to_le32(new_ea_inode->i_ino);
>> } else if (i->value_len) {
>> - size_t size = EXT4_XATTR_SIZE(i->value_len);
>> - void *val = s->base + min_offs - size;
>> - s->here->e_value_offs = cpu_to_le16(min_offs - size);
>> - s->here->e_value_inum = 0;
>> + void *val = s->base + min_offs - new_size;
>> +
>> + here->e_value_offs = cpu_to_le16(min_offs - new_size);
>> if (i->value == EXT4_ZERO_XATTR_VALUE) {
>> - memset(val, 0, size);
>> + memset(val, 0, new_size);
>> } else {
>> - /* Clear the pad bytes first. */
>> - memset(val + size - EXT4_XATTR_PAD, 0,
>> - EXT4_XATTR_PAD);
>> memcpy(val, i->value, i->value_len);
>> + /* Clear padding bytes. */
>> + memset(val + i->value_len, 0,
>> + new_size - i->value_len);
>> }
>> }
>> - s->here->e_value_size = cpu_to_le32(i->value_len);
>> + here->e_value_size = cpu_to_le32(i->value_len);
>> }
>> -
>> + ret = 0;
>> out:
>> - return rc;
>> + iput(old_ea_inode);
>> + iput(new_ea_inode);
>> + return ret;
>> }
>>
>> struct ext4_xattr_block_find {
>> @@ -1224,6 +1642,8 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
>> struct mb_cache_entry *ce = NULL;
>> int error = 0;
>> struct mb_cache *ext4_mb_cache = EXT4_GET_MB_CACHE(inode);
>> + struct inode *ea_inode = NULL;
>> + size_t old_ea_inode_size = 0;
>>
>> #define header(x) ((struct ext4_xattr_header *)(x))
>>
>> @@ -1278,6 +1698,24 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
>> header(s->base)->h_refcount = cpu_to_le32(1);
>> s->here = ENTRY(s->base + offset);
>> s->end = s->base + bs->bh->b_size;
>> +
>> + /*
>> + * If existing entry points to an xattr inode, we need
>> + * to prevent ext4_xattr_set_entry() from decrementing
>> + * ref count on it because the reference belongs to the
>> + * original block. In this case, make the entry look
>> + * like it has an empty value.
>> + */
>> + if (!s->not_found && s->here->e_value_inum) {
>> + /*
>> + * Defer quota free call for previous inode
>> + * until success is guaranteed.
>> + */
>> + old_ea_inode_size = le32_to_cpu(
>> + s->here->e_value_size);
>> + s->here->e_value_inum = 0;
>> + s->here->e_value_size = 0;
>> + }
>> }
>> } else {
>> /* Allocate a buffer where we construct the new block. */
>> @@ -1299,6 +1737,24 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
>> goto bad_block;
>> if (error)
>> goto cleanup;
>> +
>> + if (i->value && s->here->e_value_inum) {
>> + unsigned int ea_ino;
>> +
>> + /*
>> + * A ref count on ea_inode has been taken as part of the call to
>> + * ext4_xattr_set_entry() above. We would like to drop this
>> + * extra ref but we have to wait until the xattr block is
>> + * initialized and has its own ref count on the ea_inode.
>> + */
>> + ea_ino = le32_to_cpu(s->here->e_value_inum);
>> + error = ext4_xattr_inode_iget(inode, ea_ino, &ea_inode);
>> + if (error) {
>> + ea_inode = NULL;
>> + goto cleanup;
>> + }
>> + }
>> +
>> if (!IS_LAST_ENTRY(s->first))
>> ext4_xattr_rehash(header(s->base), s->here);
>>
>> @@ -1409,6 +1865,22 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
>> EXT4_FREE_BLOCKS_METADATA);
>> goto cleanup;
>> }
>> + error = ext4_xattr_inode_inc_ref_all(handle, inode,
>> + ENTRY(header(s->base)+1));
>> + if (error)
>> + goto getblk_failed;
>> + if (ea_inode) {
>> + /* Drop the extra ref on ea_inode. */
>> + error = ext4_xattr_inode_dec_ref(handle,
>> + ea_inode);
>> + if (error)
>> + ext4_warning_inode(ea_inode,
>> + "dec ref error=%d",
>> + error);
>> + iput(ea_inode);
>> + ea_inode = NULL;
>> + }
>> +
>> lock_buffer(new_bh);
>> error = ext4_journal_get_create_access(handle, new_bh);
>> if (error) {
>> @@ -1428,15 +1900,38 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
>> }
>> }
>>
>> + if (old_ea_inode_size)
>> + ext4_xattr_inode_free_quota(inode, old_ea_inode_size);
>> +
>> /* Update the inode. */
>> EXT4_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
>>
>> /* Drop the previous xattr block. */
>> - if (bs->bh && bs->bh != new_bh)
>> - ext4_xattr_release_block(handle, inode, bs->bh);
>> + if (bs->bh && bs->bh != new_bh) {
>> + struct ext4_xattr_inode_array *ea_inode_array = NULL;
>> +
>> + ext4_xattr_release_block(handle, inode, bs->bh,
>> + &ea_inode_array,
>> + 0 /* extra_credits */);
>> + ext4_xattr_inode_array_free(ea_inode_array);
>> + }
>> error = 0;
>>
>> cleanup:
>> + if (ea_inode) {
>> + int error2;
>> +
>> + error2 = ext4_xattr_inode_dec_ref(handle, ea_inode);
>> + if (error2)
>> + ext4_warning_inode(ea_inode, "dec ref error=%d",
>> + error2);
>> +
>> + /* If there was an error, revert the quota charge. */
>> + if (error)
>> + ext4_xattr_inode_free_quota(inode,
>> + i_size_read(ea_inode));
>> + iput(ea_inode);
>> + }
>> if (ce)
>> mb_cache_entry_put(ext4_mb_cache, ce);
>> brelse(new_bh);
>> @@ -1561,6 +2056,22 @@ static int ext4_xattr_value_same(struct ext4_xattr_search *s,
>> return !memcmp(value, i->value, i->value_len);
>> }
>>
>> +static struct buffer_head *ext4_xattr_get_block(struct inode *inode)
>> +{
>> + struct buffer_head *bh;
>> + int error;
>> +
>> + if (!EXT4_I(inode)->i_file_acl)
>> + return NULL;
>> + bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
>> + if (!bh)
>> + return ERR_PTR(-EIO);
>> + error = ext4_xattr_check_block(inode, bh);
>> + if (error)
>> + return ERR_PTR(error);
>> + return bh;
>> +}
>> +
>> /*
>> * ext4_xattr_set_handle()
>> *
>> @@ -1603,9 +2114,18 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
>>
>> /* Check journal credits under write lock. */
>> if (ext4_handle_valid(handle)) {
>> + struct buffer_head *bh;
>> int credits;
>>
>> - credits = ext4_xattr_set_credits(inode, value_len);
>> + bh = ext4_xattr_get_block(inode);
>> + if (IS_ERR(bh)) {
>> + error = PTR_ERR(bh);
>> + goto cleanup;
>> + }
>> +
>> + credits = __ext4_xattr_set_credits(inode->i_sb, bh, value_len);
>> + brelse(bh);
>> +
>> if (!ext4_handle_has_enough_credits(handle, credits)) {
>> error = -ENOSPC;
>> goto cleanup;
>> @@ -1641,6 +2161,7 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
>> if (flags & XATTR_CREATE)
>> goto cleanup;
>> }
>> +
>> if (!value) {
>> if (!is.s.not_found)
>> error = ext4_xattr_ibody_set(handle, inode, &i, &is);
>> @@ -1709,34 +2230,29 @@ ext4_xattr_set_handle(handle_t *handle, struct inode *inode, int name_index,
>> return error;
>> }
>>
>> -int ext4_xattr_set_credits(struct inode *inode, size_t value_len)
>> +int ext4_xattr_set_credits(struct inode *inode, size_t value_len, int *credits)
>> {
>> - struct super_block *sb = inode->i_sb;
>> - int credits;
>> -
>> - if (!EXT4_SB(sb)->s_journal)
>> - return 0;
>> + struct buffer_head *bh;
>> + int err;
>>
>> - credits = EXT4_DATA_TRANS_BLOCKS(inode->i_sb);
>> + *credits = 0;
>>
>> - /*
>> - * In case of inline data, we may push out the data to a block,
>> - * so we need to reserve credits for this eventuality
>> - */
>> - if (ext4_has_inline_data(inode))
>> - credits += ext4_writepage_trans_blocks(inode) + 1;
>> -
>> - if (ext4_has_feature_ea_inode(sb)) {
>> - int nrblocks = (value_len + sb->s_blocksize - 1) >>
>> - sb->s_blocksize_bits;
>> + if (!EXT4_SB(inode->i_sb)->s_journal)
>> + return 0;
>>
>> - /* For new inode */
>> - credits += EXT4_SINGLEDATA_TRANS_BLOCKS(sb) + 3;
>> + down_read(&EXT4_I(inode)->xattr_sem);
>>
>> - /* For data blocks of EA inode */
>> - credits += ext4_meta_trans_blocks(inode, nrblocks, 0);
>> + bh = ext4_xattr_get_block(inode);
>> + if (IS_ERR(bh)) {
>> + err = PTR_ERR(bh);
>> + } else {
>> + *credits = __ext4_xattr_set_credits(inode->i_sb, bh, value_len);
>> + brelse(bh);
>> + err = 0;
>> }
>> - return credits;
>> +
>> + up_read(&EXT4_I(inode)->xattr_sem);
>> + return err;
>> }
>>
>> /*
>> @@ -1761,7 +2277,10 @@ ext4_xattr_set(struct inode *inode, int name_index, const char *name,
>> return error;
>>
>> retry:
>> - credits = ext4_xattr_set_credits(inode, value_len);
>> + error = ext4_xattr_set_credits(inode, value_len, &credits);
>> + if (error)
>> + return error;
>> +
>> handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
>> if (IS_ERR(handle)) {
>> error = PTR_ERR(handle);
>> @@ -2067,10 +2586,10 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
>> return error;
>> }
>>
>> -
>> #define EIA_INCR 16 /* must be 2^n */
>> #define EIA_MASK (EIA_INCR - 1)
>> -/* Add the large xattr @inode into @ea_inode_array for later deletion.
>> +
>> +/* Add the large xattr @inode into @ea_inode_array for deferred iput().
>> * If @ea_inode_array is new or full it will be grown and the old
>> * contents copied over.
>> */
>> @@ -2115,21 +2634,19 @@ ext4_expand_inode_array(struct ext4_xattr_inode_array **ea_inode_array,
>> * ext4_xattr_delete_inode()
>> *
>> * Free extended attribute resources associated with this inode. Traverse
>> - * all entries and unlink any xattr inodes associated with this inode. This
>> - * is called immediately before an inode is freed. We have exclusive
>> - * access to the inode. If an orphan inode is deleted it will also delete any
>> - * xattr block and all xattr inodes. They are checked by ext4_xattr_inode_iget()
>> - * to ensure they belong to the parent inode and were not deleted already.
>> + * all entries and decrement reference on any xattr inodes associated with this
>> + * inode. This is called immediately before an inode is freed. We have exclusive
>> + * access to the inode. If an orphan inode is deleted it will also release its
>> + * references on xattr block and xattr inodes.
>> */
>> -int
>> -ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
>> - struct ext4_xattr_inode_array **ea_inode_array,
>> - int extra_credits)
>> +int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
>> + struct ext4_xattr_inode_array **ea_inode_array,
>> + int extra_credits)
>> {
>> struct buffer_head *bh = NULL;
>> struct ext4_xattr_ibody_header *header;
>> - struct ext4_inode *raw_inode;
>> struct ext4_iloc iloc = { .bh = NULL };
>> + struct ext4_xattr_entry *entry;
>> int error;
>>
>> error = ext4_xattr_ensure_credits(handle, inode, extra_credits,
>> @@ -2141,66 +2658,71 @@ ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
>> goto cleanup;
>> }
>>
>> - if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR))
>> - goto delete_external_ea;
>> + if (ext4_has_feature_ea_inode(inode->i_sb) &&
>> + ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
>>
>> - error = ext4_get_inode_loc(inode, &iloc);
>> - if (error)
>> - goto cleanup;
>> -
>> - error = ext4_journal_get_write_access(handle, iloc.bh);
>> - if (error)
>> - goto cleanup;
>> + error = ext4_get_inode_loc(inode, &iloc);
>> + if (error) {
>> + EXT4_ERROR_INODE(inode, "inode loc (error %d)", error);
>> + goto cleanup;
>> + }
>>
>> - raw_inode = ext4_raw_inode(&iloc);
>> - header = IHDR(inode, raw_inode);
>> - ext4_xattr_inode_remove_all(handle, inode, iloc.bh, IFIRST(header),
>> - false /* block_csum */, ea_inode_array,
>> - extra_credits);
>> + error = ext4_journal_get_write_access(handle, iloc.bh);
>> + if (error) {
>> + EXT4_ERROR_INODE(inode, "write access (error %d)",
>> + error);
>> + goto cleanup;
>> + }
>>
>> -delete_external_ea:
>> - if (!EXT4_I(inode)->i_file_acl) {
>> - error = 0;
>> - goto cleanup;
>> - }
>> - bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
>> - if (!bh) {
>> - EXT4_ERROR_INODE(inode, "block %llu read error",
>> - EXT4_I(inode)->i_file_acl);
>> - error = -EIO;
>> - goto cleanup;
>> - }
>> - if (BHDR(bh)->h_magic != cpu_to_le32(EXT4_XATTR_MAGIC) ||
>> - BHDR(bh)->h_blocks != cpu_to_le32(1)) {
>> - EXT4_ERROR_INODE(inode, "bad block %llu",
>> - EXT4_I(inode)->i_file_acl);
>> - error = -EFSCORRUPTED;
>> - goto cleanup;
>> + header = IHDR(inode, ext4_raw_inode(&iloc));
>> + if (header->h_magic == cpu_to_le32(EXT4_XATTR_MAGIC))
>> + ext4_xattr_inode_dec_ref_all(handle, inode, iloc.bh,
>> + IFIRST(header),
>> + false /* block_csum */,
>> + ea_inode_array,
>> + extra_credits,
>> + false /* skip_quota */);
>> }
>>
>> - if (ext4_has_feature_ea_inode(inode->i_sb)) {
>> - error = ext4_journal_get_write_access(handle, bh);
>> - if (error) {
>> - EXT4_ERROR_INODE(inode, "write access %llu",
>> + if (EXT4_I(inode)->i_file_acl) {
>> + bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
>> + if (!bh) {
>> + EXT4_ERROR_INODE(inode, "block %llu read error",
>> EXT4_I(inode)->i_file_acl);
>> + error = -EIO;
>> + goto cleanup;
>> + }
>> + error = ext4_xattr_check_block(inode, bh);
>> + if (error) {
>> + EXT4_ERROR_INODE(inode, "bad block %llu (error %d)",
>> + EXT4_I(inode)->i_file_acl, error);
>> goto cleanup;
>> }
>> - ext4_xattr_inode_remove_all(handle, inode, bh,
>> - BFIRST(bh),
>> - true /* block_csum */,
>> - ea_inode_array,
>> - extra_credits);
>> - }
>>
>> - ext4_xattr_release_block(handle, inode, bh);
>> - /* Update i_file_acl within the same transaction that releases block. */
>> - EXT4_I(inode)->i_file_acl = 0;
>> - error = ext4_mark_inode_dirty(handle, inode);
>> - if (error) {
>> - EXT4_ERROR_INODE(inode, "mark inode dirty (error %d)",
>> - error);
>> - goto cleanup;
>> + if (ext4_has_feature_ea_inode(inode->i_sb)) {
>> + for (entry = BFIRST(bh); !IS_LAST_ENTRY(entry);
>> + entry = EXT4_XATTR_NEXT(entry))
>> + if (entry->e_value_inum)
>> + ext4_xattr_inode_free_quota(inode,
>> + le32_to_cpu(entry->e_value_size));
>> +
>> + }
>> +
>> + ext4_xattr_release_block(handle, inode, bh, ea_inode_array,
>> + extra_credits);
>> + /*
>> + * Update i_file_acl value in the same transaction that releases
>> + * block.
>> + */
>> + EXT4_I(inode)->i_file_acl = 0;
>> + error = ext4_mark_inode_dirty(handle, inode);
>> + if (error) {
>> + EXT4_ERROR_INODE(inode, "mark inode dirty (error %d)",
>> + error);
>> + goto cleanup;
>> + }
>> }
>> + error = 0;
>> cleanup:
>> brelse(iloc.bh);
>> brelse(bh);
>> @@ -2209,17 +2731,13 @@ ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
>>
>> void ext4_xattr_inode_array_free(struct ext4_xattr_inode_array *ea_inode_array)
>> {
>> - struct inode *ea_inode;
>> - int idx = 0;
>> + int idx;
>>
>> if (ea_inode_array == NULL)
>> return;
>>
>> - for (; idx < ea_inode_array->count; ++idx) {
>> - ea_inode = ea_inode_array->inodes[idx];
>> - clear_nlink(ea_inode);
>> - iput(ea_inode);
>> - }
>> + for (idx = 0; idx < ea_inode_array->count; ++idx)
>> + iput(ea_inode_array->inodes[idx]);
>> kfree(ea_inode_array);
>> }
>>
>> diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
>> index b2005a2716d9..67616cb9a059 100644
>> --- a/fs/ext4/xattr.h
>> +++ b/fs/ext4/xattr.h
>> @@ -69,19 +69,6 @@ struct ext4_xattr_entry {
>> EXT4_I(inode)->i_extra_isize))
>> #define IFIRST(hdr) ((struct ext4_xattr_entry *)((hdr)+1))
>>
>> -/*
>> - * Link EA inode back to parent one using i_mtime field.
>> - * Extra integer type conversion added to ignore higher
>> - * bits in i_mtime.tv_sec which might be set by ext4_get()
>> - */
>> -#define EXT4_XATTR_INODE_SET_PARENT(inode, inum) \
>> -do { \
>> - (inode)->i_mtime.tv_sec = inum; \
>> -} while(0)
>> -
>> -#define EXT4_XATTR_INODE_GET_PARENT(inode) \
>> -((__u32)(inode)->i_mtime.tv_sec)
>> -
>> /*
>> * The minimum size of EA value when you start storing it in an external inode
>> * size of block - size of header - size of 1 entry - 4 null bytes
>> @@ -165,9 +152,9 @@ extern ssize_t ext4_listxattr(struct dentry *, char *, size_t);
>> extern int ext4_xattr_get(struct inode *, int, const char *, void *, size_t);
>> extern int ext4_xattr_set(struct inode *, int, const char *, const void *, size_t, int);
>> extern int ext4_xattr_set_handle(handle_t *, struct inode *, int, const char *, const void *, size_t, int);
>> -extern int ext4_xattr_set_credits(struct inode *inode, size_t value_len);
>> +extern int ext4_xattr_set_credits(struct inode *inode, size_t value_len,
>> + int *credits);
>>
>> -extern int ext4_xattr_inode_unlink(struct inode *inode, unsigned long ea_ino);
>> extern int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
>> struct ext4_xattr_inode_array **array,
>> int extra_credits);
>> diff --git a/fs/mbcache.c b/fs/mbcache.c
>> index 45a8d52dc991..d818fd236787 100644
>> --- a/fs/mbcache.c
>> +++ b/fs/mbcache.c
>> @@ -13,10 +13,11 @@
>> * mb_cache_entry_delete()).
>> *
>> * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
>> - * They use hash of a block contents as a key and block number as a value.
>> - * That's why keys need not be unique (different xattr blocks may end up having
>> - * the same hash). However block number always uniquely identifies a cache
>> - * entry.
>> + * Ext4 also uses it for deduplication of xattr values stored in inodes.
>> + * They use hash of data as a key and provide a value that may represent a
>> + * block or inode number. That's why keys need not be unique (hash of different
>> + * data may be the same). However user provided value always uniquely
>> + * identifies a cache entry.
>> *
>> * We provide functions for creation and removal of entries, search by key,
>> * and a special "delete entry with given key-value pair" operation. Fixed
>> --
>> 2.13.1.518.g3df882009-goog
>>
Cheers, Andreas
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