[PATCH V10 06/19] fs/buffer.c: use bvec iterator to truncate the bio

[Omar Sandoval]

On Thu, Nov 15, 2018 at 04:52:53PM +0800, Ming Lei wrote:
> Once multi-page bvec is enabled, the last bvec may include more than one
> page, this patch use bvec_last_segment() to truncate the bio.
> 
> Cc: Dave Chinner <dchinner at redhat.com>
> Cc: Kent Overstreet <kent.overstreet at gmail.com>
> Cc: Mike Snitzer <snitzer at redhat.com>
> Cc: dm-devel at redhat.com
> Cc: Alexander Viro <viro at zeniv.linux.org.uk>
> Cc: linux-fsdevel at vger.kernel.org
> Cc: Shaohua Li <shli at kernel.org>
> Cc: linux-raid at vger.kernel.org
> Cc: linux-erofs at lists.ozlabs.org
> Cc: David Sterba <dsterba at suse.com>
> Cc: linux-btrfs at vger.kernel.org
> Cc: Darrick J. Wong <darrick.wong at oracle.com>
> Cc: linux-xfs at vger.kernel.org
> Cc: Gao Xiang <gaoxiang25 at huawei.com>
> Cc: Christoph Hellwig <hch at lst.de>
> Cc: Theodore Ts'o <tytso at mit.edu>
> Cc: linux-ext4 at vger.kernel.org
> Cc: Coly Li <colyli at suse.de>
> Cc: linux-bcache at vger.kernel.org
> Cc: Boaz Harrosh <ooo at electrozaur.com>
> Cc: Bob Peterson <rpeterso at redhat.com>
> Cc: cluster-devel at redhat.com

Reviewed-by: Omar Sandoval <osandov at fb.com>

> Signed-off-by: Ming Lei <ming.lei at redhat.com>
> ---
>  fs/buffer.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 1286c2b95498..fa37ad52e962 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -3032,7 +3032,10 @@ void guard_bio_eod(int op, struct bio *bio)
>  
>  	/* ..and clear the end of the buffer for reads */
>  	if (op == REQ_OP_READ) {
> -		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
> +		struct bio_vec bv;
> +
> +		bvec_last_segment(bvec, &bv);
> +		zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
>  				truncated_bytes);
>  	}
>  }
> -- 
> 2.9.5
>