4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tahsin Erdogan tahsin@google.com
commit ec00022030da5761518476096626338bd67df57a upstream.
When an xattr block has a single reference, block is updated inplace and it is reinserted to the cache. Later, a cache lookup is performed to see whether an existing block has the same contents. This cache lookup will most of the time return the just inserted entry so deduplication is not achieved.
Running the following test script will produce two xattr blocks which can be observed in "File ACL: " line of debugfs output:
mke2fs -b 1024 -I 128 -F -O extent /dev/sdb 1G mount /dev/sdb /mnt/sdb
touch /mnt/sdb/{x,y}
setfattr -n user.1 -v aaa /mnt/sdb/x setfattr -n user.2 -v bbb /mnt/sdb/x
setfattr -n user.1 -v aaa /mnt/sdb/y setfattr -n user.2 -v bbb /mnt/sdb/y
debugfs -R 'stat x' /dev/sdb | cat debugfs -R 'stat y' /dev/sdb | cat
This patch defers the reinsertion to the cache so that we can locate other blocks with the same contents.
Signed-off-by: Tahsin Erdogan tahsin@google.com Signed-off-by: Theodore Ts'o tytso@mit.edu Reviewed-by: Andreas Dilger adilger@dilger.ca Signed-off-by: Tommi Rantala tommi.t.rantala@nokia.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/ext4/xattr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -828,8 +828,6 @@ ext4_xattr_block_set(handle_t *handle, s if (!IS_LAST_ENTRY(s->first)) ext4_xattr_rehash(header(s->base), s->here); - ext4_xattr_cache_insert(ext4_mb_cache, - bs->bh); } unlock_buffer(bs->bh); if (error == -EFSCORRUPTED) @@ -918,6 +916,7 @@ inserted: } else if (bs->bh && s->base == bs->bh->b_data) { /* We were modifying this block in-place. */ ea_bdebug(bs->bh, "keeping this block"); + ext4_xattr_cache_insert(ext4_mb_cache, bs->bh); new_bh = bs->bh; get_bh(new_bh); } else {