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btrfs: fix RAID direct I/O reads with alternate csums 

commit e7a04894c7 upstream.

btrfs_lookup_and_bind_dio_csum() does pointer arithmetic which assumes
32-bit checksums. If using a larger checksum, this leads to spurious
failures when a direct I/O read crosses a stripe. This is easy
to reproduce:

  # mkfs.btrfs -f --checksum blake2 -d raid0 /dev/vdc /dev/vdd
  ...
  # mount /dev/vdc /mnt
  # cd /mnt
  # dd if=/dev/urandom of=foo bs=1M count=1 status=none
  # dd if=foo of=/dev/null bs=1M iflag=direct status=none
  dd: error reading 'foo': Input/output error
  # dmesg | tail -1
  [  135.821568] BTRFS warning (device vdc): csum failed root 5 ino 257 off 421888 ...

Fix it by using the actual checksum size.

Fixes: 1e25a2e3ca ("btrfs: don't assume ordered sums to be 4 bytes")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Omar Sandoval 2020-03-02 14:02:49 -08:00 committed by Greg Kroah-Hartman
parent 557693d1d3
commit 0c8eccc28e
1 changed files with 3 additions and 1 deletions
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4
fs/btrfs/inode.c
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@ -8426,6 +8426,7 @@ static inline blk_status_t btrfs_lookup_and_bind_dio_csum(struct inode *inode,
{
struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
struct btrfs_io_bio *orig_io_bio = btrfs_io_bio(dip->orig_bio);
u16 csum_size;
blk_status_t ret;
/*
@ -8445,7 +8446,8 @@ static inline blk_status_t btrfs_lookup_and_bind_dio_csum(struct inode *inode,
file_offset -= dip->logical_offset;
file_offset >>= inode->i_sb->s_blocksize_bits;
io_bio->csum = (u8 *)(((u32 *)orig_io_bio->csum) + file_offset);
csum_size = btrfs_super_csum_size(btrfs_sb(inode->i_sb)->super_copy);
io_bio->csum = orig_io_bio->csum + csum_size * file_offset;
return 0;
}