From e7a04894c766daa4248cb736efee93550f2d5872 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Mon, 2 Mar 2020 14:02:49 -0800 Subject: [PATCH] btrfs: fix RAID direct I/O reads with alternate csums 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: 1e25a2e3ca0d ("btrfs: don't assume ordered sums to be 4 bytes") CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Johannes Thumshirn Signed-off-by: Omar Sandoval Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 1ccb3f8..27076eb 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -7783,6 +7783,7 @@ 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; /* @@ -7802,7 +7803,8 @@ 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; } -- 2.7.4