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

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Message-ID: <20170626180401.GB31661@lim.localdomain>
Date:   Mon, 26 Jun 2017 11:04:01 -0700
From:   Liu Bo <bo.li.liu@...cle.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...com>, Christoph Hellwig <hch@...radead.org>,
        Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH v2 14/51] btrfs: avoid to access bvec table directly for
 a cloned bio

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@...cle.com>

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