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

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Date:   Thu, 15 Nov 2018 16:20:20 -0800
From:   Omar Sandoval <osandov@...ndov.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Dave Chinner <dchinner@...hat.com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, Shaohua Li <shli@...nel.org>,
        linux-raid@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Gao Xiang <gaoxiang25@...wei.com>,
        Christoph Hellwig <hch@....de>, Theodore Ts'o <tytso@....edu>,
        linux-ext4@...r.kernel.org, Coly Li <colyli@...e.de>,
        linux-bcache@...r.kernel.org, Boaz Harrosh <ooo@...ctrozaur.com>,
        Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com
Subject: Re: [PATCH V10 06/19] fs/buffer.c: use bvec iterator to truncate the
 bio

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@...hat.com>
> Cc: Kent Overstreet <kent.overstreet@...il.com>
> Cc: Mike Snitzer <snitzer@...hat.com>
> Cc: dm-devel@...hat.com
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: Shaohua Li <shli@...nel.org>
> Cc: linux-raid@...r.kernel.org
> Cc: linux-erofs@...ts.ozlabs.org
> Cc: David Sterba <dsterba@...e.com>
> Cc: linux-btrfs@...r.kernel.org
> Cc: Darrick J. Wong <darrick.wong@...cle.com>
> Cc: linux-xfs@...r.kernel.org
> Cc: Gao Xiang <gaoxiang25@...wei.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: Theodore Ts'o <tytso@....edu>
> Cc: linux-ext4@...r.kernel.org
> Cc: Coly Li <colyli@...e.de>
> Cc: linux-bcache@...r.kernel.org
> Cc: Boaz Harrosh <ooo@...ctrozaur.com>
> Cc: Bob Peterson <rpeterso@...hat.com>
> Cc: cluster-devel@...hat.com

Reviewed-by: Omar Sandoval <osandov@...com>

> Signed-off-by: Ming Lei <ming.lei@...hat.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
>