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

Liu Bo
2017-06-26T18:04:01Z

On Mon, Jun 26, 2017 at 08:09:57PM +0800, Ming Lei wrote:
> 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.
>

Looks good to me.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

-liubo
> Cc: Chris Mason <clm@fb.com>
> Cc: Josef Bacik <jbacik@fb.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: linux-btrfs@vger.kernel.org
> Cc: Liu Bo <bo.li.liu@oracle.com>
> Signed-off-by: Ming Lei <ming.lei@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
>