linux-kernel - Re: [PATCH v2 16/51] block: bounce: avoid direct access to bvec table

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Date:   Tue, 27 Jun 2017 15:34:55 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
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
Subject: Re: [PATCH v2 16/51] block: bounce: avoid direct access to bvec table

On Mon, Jun 26, 2017 at 11:12:11PM -0700, Matthew Wilcox wrote:
> On Mon, Jun 26, 2017 at 08:09:59PM +0800, Ming Lei wrote:
> >  	bio_for_each_segment_all(bvec, bio, i) {
> > -		org_vec = bio_orig->bi_io_vec + i + start;
> > -
> > -		if (bvec->bv_page == org_vec->bv_page)
> > -			continue;
> > +		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
> > +		if (bvec->bv_page == orig_vec.bv_page)
> > +			goto next;
> >  
> >  		dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
> >  		mempool_free(bvec->bv_page, pool);
> > + next:
> > +		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
> >  	}
> >  
> 
> I think this might be written more clearly as:
> 
>  	bio_for_each_segment_all(bvec, bio, i) {
> 		orig_vec = bio_iter_iovec(bio_orig, orig_iter);
> 		if (bvec->bv_page != orig_vec.bv_page) {
>  			dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
> 	 		mempool_free(bvec->bv_page, pool);
> 		}
> 		bio_advance_iter(bio_orig, &orig_iter, orig_vec.bv_len);
>  	}
> 
> What do you think?

Yeah, looks the above code is more clean, will do it in V3.

thanks,
Ming