[PATCH v2 14/51] btrfs: avoid to access bvec table directly for a cloned bio

[Ming Lei]

Commit 17347cec15f919901c90(Btrfs: change how we iterate bios in endio)
mentioned that for dio the submitted bio may be fast cloned, we
can't access the bvec table directly for a cloned bio, so use
bio_get_first_bvec() to retrieve the 1st bvec.

Cc: Chris Mason <c...@fb.com>
Cc: Josef Bacik <jba...@fb.com>
Cc: David Sterba <dste...@suse.com>
Cc: linux-bt...@vger.kernel.org
Cc: Liu Bo <bo.li....@oracle.com>
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 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 06dea7c89bbd..4ab02b34f029 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7993,6 +7993,7 @@ static int dio_read_error(struct inode *inode, struct bio 
*failed_bio,
        int read_mode = 0;
        int segs;
        int ret;
+       struct bio_vec bvec;
 
        BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
 
@@ -8008,8 +8009,9 @@ static int dio_read_error(struct inode *inode, struct bio 
*failed_bio,
        }
 
        segs = bio_segments(failed_bio);
+       bio_get_first_bvec(failed_bio, &bvec);
        if (segs > 1 ||
-           (failed_bio->bi_io_vec->bv_len > btrfs_inode_sectorsize(inode)))
+           (bvec.bv_len > btrfs_inode_sectorsize(inode)))
                read_mode |= REQ_FAILFAST_DEV;
 
        isector = start - btrfs_io_bio(failed_bio)->logical;
-- 
2.9.4