>From b98ae025141361b9e92fdd470dfd2314a64a47d0 Mon Sep 17 00:00:00 2001 From: Tahsin Erdogan Date: Sat, 5 Aug 2017 22:41:42 -0400 Subject: [PATCH] ext4: inplace xattr block update fails to deduplicate blocks 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 Signed-off-by: Theodore Ts'o Reviewed-by: Andreas Dilger Signed-off-by: Tommi Rantala --- fs/ext4/xattr.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 3eeed8f0aa06..3fadfabcac39 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -837,8 +837,6 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode, if (!IS_LAST_ENTRY(s->first)) ext4_xattr_rehash(header(s->base), s->here); - ext4_xattr_cache_insert(ext4_mb_cache, - bs->bh); } ext4_xattr_block_csum_set(inode, bs->bh); unlock_buffer(bs->bh); @@ -959,6 +957,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode, } 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 { -- 2.14.3