by Shaohua Li

[permalink] [raw]

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

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 <[email protected]>
> > > Cc: [email protected]
> > > Signed-off-by: Ming Lei <[email protected]>
> > > ---
> > > 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