Re: [PATCH v2 11/51] md: raid1: initialize bvec table via bio_add_page()

[Shaohua Li]

On Wed, Jun 28, 2017 at 12:22:51AM +0800, Ming Lei wrote:
> On Tue, Jun 27, 2017 at 05:36:39PM +0800, Guoqing Jiang wrote:
> > 
> > 
> > On 06/26/2017 08:09 PM, Ming Lei wrote:
> > > We will support multipage bvec soon, so initialize bvec
> > > table using the standardy way instead of writing the
> > > talbe directly. Otherwise it won't work any more once
> > > multipage bvec is enabled.
> > > 
> > > Cc: Shaohua Li <shli@xxxxxxxxxx>
> > > Cc: linux-raid@xxxxxxxxxxxxxxx
> > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> > > ---
> > >   drivers/md/raid1.c | 27 ++++++++++++++-------------
> > >   1 file changed, 14 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> > > index 3febfc8391fb..835c42396861 100644
> > > --- a/drivers/md/raid1.c
> > > +++ b/drivers/md/raid1.c
> > > @@ -2086,10 +2086,8 @@ static void process_checks(struct r1bio *r1_bio)
> > >   	/* Fix variable parts of all bios */
> > >   	vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
> > >   	for (i = 0; i < conf->raid_disks * 2; i++) {
> > > -		int j;
> > >   		int size;
> > >   		blk_status_t status;
> > > -		struct bio_vec *bi;
> > >   		struct bio *b = r1_bio->bios[i];
> > >   		struct resync_pages *rp = get_resync_pages(b);
> > >   		if (b->bi_end_io != end_sync_read)
> > > @@ -2098,8 +2096,6 @@ static void process_checks(struct r1bio *r1_bio)
> > >   		status = b->bi_status;
> > >   		bio_reset(b);
> > >   		b->bi_status = status;
> > > -		b->bi_vcnt = vcnt;
> > > -		b->bi_iter.bi_size = r1_bio->sectors << 9;
> > >   		b->bi_iter.bi_sector = r1_bio->sector +
> > >   			conf->mirrors[i].rdev->data_offset;
> > >   		b->bi_bdev = conf->mirrors[i].rdev->bdev;
> > > @@ -2107,15 +2103,20 @@ static void process_checks(struct r1bio *r1_bio)
> > >   		rp->raid_bio = r1_bio;
> > >   		b->bi_private = rp;
> > > -		size = b->bi_iter.bi_size;
> > > -		bio_for_each_segment_all(bi, b, j) {
> > > -			bi->bv_offset = 0;
> > > -			if (size > PAGE_SIZE)
> > > -				bi->bv_len = PAGE_SIZE;
> > > -			else
> > > -				bi->bv_len = size;
> > > -			size -= PAGE_SIZE;
> > > -		}
> > > +		/* initialize bvec table again */
> > > +		rp->idx = 0;
> > > +		size = r1_bio->sectors << 9;
> > > +		do {
> > > +			struct page *page = resync_fetch_page(rp, rp->idx++);
> > > +			int len = min_t(int, size, PAGE_SIZE);
> > > +
> > > +			/*
> > > +			 * won't fail because the vec table is big
> > > +			 * enough to hold all these pages
> > > +			 */
> > > +			bio_add_page(b, page, len, 0);
> > > +			size -= len;
> > > +		} while (rp->idx < RESYNC_PAGES && size > 0);
> > >   	}
> > 
> > Seems above section is similar as reset_bvec_table introduced in next patch,
> > why there is difference between raid1 and raid10? Maybe add reset_bvec_table
> > into md.c, then call it in raid1 or raid10 is better, just my 2 cents.
> 
> Hi Guoqing,
> 
> I think it is a good idea, and even the two patches can be put into
> one, so how about the following patch?
> 
> Shaohua, what do you think of this one?

generally looks good.
 
> ---
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 3d957ac1e109..7ffc622dd7fa 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -9126,6 +9126,24 @@ void md_reload_sb(struct mddev *mddev, int nr)
>  }
>  EXPORT_SYMBOL(md_reload_sb);
>  
> +/* generally called after bio_reset() for reseting bvec */
> +void reset_bvec_table(struct bio *bio, struct resync_pages *rp, int size)
> +{
> +	/* initialize bvec table again */
> +	rp->idx = 0;
> +	do {
> +		struct page *page = resync_fetch_page(rp, rp->idx++);
> +		int len = min_t(int, size, PAGE_SIZE);
> +
> +		/*
> +		 * won't fail because the vec table is big
> +		 * enough to hold all these pages
> +		 */
> +		bio_add_page(bio, page, len, 0);
> +		size -= len;
> +	} while (rp->idx < RESYNC_PAGES && size > 0);
> +}
> +

used in raid1/10, so must export the symbol. Then please not pollute global
names, maybe call it md_bio_reset_resync_pages?

>  #ifndef MODULE
>  
>  /*
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 991f0fe2dcc6..f569831b1de9 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -783,4 +783,6 @@ static inline struct page *resync_fetch_page(struct resync_pages *rp,
>  		return NULL;
>  	return rp->pages[idx];
>  }
> +
> +void reset_bvec_table(struct bio *bio, struct resync_pages *rp, int size);
>  #endif /* _MD_MD_H */
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 3febfc8391fb..6ae2665ecd58 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -2086,10 +2086,7 @@ static void process_checks(struct r1bio *r1_bio)
>  	/* Fix variable parts of all bios */
>  	vcnt = (r1_bio->sectors + PAGE_SIZE / 512 - 1) >> (PAGE_SHIFT - 9);
>  	for (i = 0; i < conf->raid_disks * 2; i++) {
> -		int j;
> -		int size;
>  		blk_status_t status;
> -		struct bio_vec *bi;
>  		struct bio *b = r1_bio->bios[i];
>  		struct resync_pages *rp = get_resync_pages(b);
>  		if (b->bi_end_io != end_sync_read)
> @@ -2098,8 +2095,6 @@ static void process_checks(struct r1bio *r1_bio)
>  		status = b->bi_status;
>  		bio_reset(b);
>  		b->bi_status = status;
> -		b->bi_vcnt = vcnt;
> -		b->bi_iter.bi_size = r1_bio->sectors << 9;
>  		b->bi_iter.bi_sector = r1_bio->sector +
>  			conf->mirrors[i].rdev->data_offset;
>  		b->bi_bdev = conf->mirrors[i].rdev->bdev;
> @@ -2107,15 +2102,8 @@ static void process_checks(struct r1bio *r1_bio)
>  		rp->raid_bio = r1_bio;
>  		b->bi_private = rp;
>  
> -		size = b->bi_iter.bi_size;
> -		bio_for_each_segment_all(bi, b, j) {
> -			bi->bv_offset = 0;
> -			if (size > PAGE_SIZE)
> -				bi->bv_len = PAGE_SIZE;
> -			else
> -				bi->bv_len = size;
> -			size -= PAGE_SIZE;
> -		}
> +		/* initialize bvec table again */
> +		reset_bvec_table(b, rp, r1_bio->sectors << 9);
>  	}
>  	for (primary = 0; primary < conf->raid_disks * 2; primary++)
>  		if (r1_bio->bios[primary]->bi_end_io == end_sync_read &&
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 5026e7ad51d3..72f4fa07449b 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -2087,8 +2087,8 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>  		rp = get_resync_pages(tbio);
>  		bio_reset(tbio);
>  
> -		tbio->bi_vcnt = vcnt;
> -		tbio->bi_iter.bi_size = fbio->bi_iter.bi_size;
> +		reset_bvec_table(tbio, rp, fbio->bi_iter.bi_size);
> +
>  		rp->raid_bio = r10_bio;
>  		tbio->bi_private = rp;
>  		tbio->bi_iter.bi_sector = r10_bio->devs[i].addr;
> 
> Thanks,
> Ming