On Sep 28, 2015 11:57, <fdmanana@xxxxxxxxxx> wrote:
>
> From: Filipe Manana <fdmanana@xxxxxxxx>
>
> 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
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
> ---
> fs/btrfs/extent_io.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 11aa8f7..363726b 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3144,12 +3144,12 @@ static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
> 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) {
> @@ -3165,7 +3165,7 @@ static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
>
> 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]);
> }
> }
> @@ -3175,7 +3175,8 @@ static void __extent_readpages(struct extent_io_tree *tree,
> 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;
> @@ -3196,7 +3197,7 @@ static void __extent_readpages(struct extent_io_tree *tree,
> 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;
> @@ -3207,7 +3208,8 @@ static void __extent_readpages(struct extent_io_tree *tree,
> __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,
> @@ -4218,6 +4220,7 @@ int extent_readpages(struct extent_io_tree *tree,
> 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);
> @@ -4234,12 +4237,12 @@ int extent_readpages(struct extent_io_tree *tree,
> 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);
> --
> 2.1.3
Tested-by: Timofey Titovets <nefelim4ag@xxxxxxxxx>
Thanks, Again, Filipe
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