This is a note to let you know that I've just added the patch titled Btrfs: update fix for read corruption of compressed and shared extents to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: btrfs-update-fix-for-read-corruption-of-compressed-and-shared-extents.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 808f80b46790f27e145c72112189d6a3be2bc884 Mon Sep 17 00:00:00 2001 From: Filipe Manana <fdmanana@xxxxxxxx> Date: Mon, 28 Sep 2015 09:56:26 +0100 Subject: Btrfs: update fix for read corruption of compressed and shared extents From: Filipe Manana <fdmanana@xxxxxxxx> commit 808f80b46790f27e145c72112189d6a3be2bc884 upstream. My previous fix in commit 005efedf2c7d ("Btrfs: fix read corruption of compressed and shared extents") was effective only if the compressed extents cover a file range with a length that is not a multiple of 16 pages. That's because the detection of when we reached a different range of the file that shares the same compressed extent as the previously processed range was done at extent_io.c:__do_contiguous_readpages(), which covers subranges with a length up to 16 pages, because extent_readpages() groups the pages in clusters no larger than 16 pages. So fix this by tracking the start of the previously processed file range's extent map at extent_readpages(). The following test case for fstests reproduces the issue: seq=`basename $0` seqres=$RESULT_DIR/$seq echo "QA output created by $seq" tmp=/tmp/$$ status=1 # failure is the default! trap "_cleanup; exit \$status" 0 1 2 3 15 _cleanup() { rm -f $tmp.* } # get standard environment, filters and checks . ./common/rc . ./common/filter # real QA test starts here _need_to_be_root _supported_fs btrfs _supported_os Linux _require_scratch _require_cloner rm -f $seqres.full test_clone_and_read_compressed_extent() { local mount_opts=$1 _scratch_mkfs >>$seqres.full 2>&1 _scratch_mount $mount_opts # Create our test file with a single extent of 64Kb that is going to # be compressed no matter which compression algo is used (zlib/lzo). $XFS_IO_PROG -f -c "pwrite -S 0xaa 0K 64K" \ $SCRATCH_MNT/foo | _filter_xfs_io # Now clone the compressed extent into an adjacent file offset. $CLONER_PROG -s 0 -d $((64 * 1024)) -l $((64 * 1024)) \ $SCRATCH_MNT/foo $SCRATCH_MNT/foo echo "File digest before unmount:" md5sum $SCRATCH_MNT/foo | _filter_scratch # Remount the fs or clear the page cache to trigger the bug in # btrfs. Because the extent has an uncompressed length that is a # multiple of 16 pages, all the pages belonging to the second range # of the file (64K to 128K), which points to the same extent as the # first range (0K to 64K), had their contents full of zeroes instead # of the byte 0xaa. This was a bug exclusively in the read path of # compressed extents, the correct data was stored on disk, btrfs # just failed to fill in the pages correctly. _scratch_remount echo "File digest after remount:" # Must match the digest we got before. md5sum $SCRATCH_MNT/foo | _filter_scratch } echo -e "\nTesting with zlib compression..." test_clone_and_read_compressed_extent "-o compress=zlib" _scratch_unmount echo -e "\nTesting with lzo compression..." test_clone_and_read_compressed_extent "-o compress=lzo" status=0 exit Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx> Tested-by: Timofey Titovets <nefelim4ag@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/extent_io.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3012,12 +3012,12 @@ static inline void __do_contiguous_readp get_extent_t *get_extent, struct extent_map **em_cached, struct bio **bio, int mirror_num, - unsigned long *bio_flags, int rw) + unsigned long *bio_flags, int rw, + u64 *prev_em_start) { struct inode *inode; struct btrfs_ordered_extent *ordered; int index; - u64 prev_em_start = (u64)-1; inode = pages[0]->mapping->host; while (1) { @@ -3033,7 +3033,7 @@ static inline void __do_contiguous_readp for (index = 0; index < nr_pages; index++) { __do_readpage(tree, pages[index], get_extent, em_cached, bio, - mirror_num, bio_flags, rw, &prev_em_start); + mirror_num, bio_flags, rw, prev_em_start); page_cache_release(pages[index]); } } @@ -3043,7 +3043,8 @@ static void __extent_readpages(struct ex int nr_pages, get_extent_t *get_extent, struct extent_map **em_cached, struct bio **bio, int mirror_num, - unsigned long *bio_flags, int rw) + unsigned long *bio_flags, int rw, + u64 *prev_em_start) { u64 start = 0; u64 end = 0; @@ -3064,7 +3065,7 @@ static void __extent_readpages(struct ex index - first_index, start, end, get_extent, em_cached, bio, mirror_num, bio_flags, - rw); + rw, prev_em_start); start = page_start; end = start + PAGE_CACHE_SIZE - 1; first_index = index; @@ -3075,7 +3076,8 @@ static void __extent_readpages(struct ex __do_contiguous_readpages(tree, &pages[first_index], index - first_index, start, end, get_extent, em_cached, bio, - mirror_num, bio_flags, rw); + mirror_num, bio_flags, rw, + prev_em_start); } static int __extent_read_full_page(struct extent_io_tree *tree, @@ -3967,6 +3969,7 @@ int extent_readpages(struct extent_io_tr struct page *page; struct extent_map *em_cached = NULL; int nr = 0; + u64 prev_em_start = (u64)-1; for (page_idx = 0; page_idx < nr_pages; page_idx++) { page = list_entry(pages->prev, struct page, lru); @@ -3983,12 +3986,12 @@ int extent_readpages(struct extent_io_tr if (nr < ARRAY_SIZE(pagepool)) continue; __extent_readpages(tree, pagepool, nr, get_extent, &em_cached, - &bio, 0, &bio_flags, READ); + &bio, 0, &bio_flags, READ, &prev_em_start); nr = 0; } if (nr) __extent_readpages(tree, pagepool, nr, get_extent, &em_cached, - &bio, 0, &bio_flags, READ); + &bio, 0, &bio_flags, READ, &prev_em_start); if (em_cached) free_extent_map(em_cached); Patches currently in stable-queue which might be from fdmanana@xxxxxxxx are queue-3.14/btrfs-fix-read-corruption-of-compressed-and-shared-extents.patch queue-3.14/btrfs-update-fix-for-read-corruption-of-compressed-and-shared-extents.patch queue-3.14/btrfs-skip-waiting-on-ordered-range-for-special-files.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html