On Jul 14, 2017, at 5:25 PM, Tahsin Erdogan <[email protected]> wrote: > > 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 <[email protected]>
Reviewed-by: Andreas Dilger <[email protected]> > --- > fs/ext4/xattr.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index cff4f41ced61..ad4ea1cf685f 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -1815,9 +1815,6 @@ ext4_xattr_block_set(handle_t *handle, struct inode > *inode, > ea_bdebug(bs->bh, "modifying in-place"); > error = ext4_xattr_set_entry(i, s, handle, inode, > true /* is_block */); > - if (!error) > - ext4_xattr_block_cache_insert(ea_block_cache, > - bs->bh); > ext4_xattr_block_csum_set(inode, bs->bh); > unlock_buffer(bs->bh); > if (error == -EFSCORRUPTED) > @@ -1973,6 +1970,7 @@ 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_block_cache_insert(ea_block_cache, bs->bh); > new_bh = bs->bh; > get_bh(new_bh); > } else { > -- > 2.13.2.932.g7449e964c-goog > Cheers, Andreas
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