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

Ming Lei
2017-06-27T16:23:14Z

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@kernel.org>
> > Cc: linux-raid@vger.kernel.org
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> > 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?

---
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);
+}
+
#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