[RESEND PATCH V5 31/33] block: bio: pass segments to bio if bio_add_page() is bypassed

[Ming Lei]

Under some situations, such as block direct I/O, we can't use
bio_add_page() for merging pages into multipage bvec, so
a new function is implemented for converting page array into one
segment array, then these cases can benefit from multipage bvec
too.

Signed-off-by: Ming Lei 
---
 block/bio.c | 54 --
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index bc3992f52fe8..b7d9089cb28f 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -913,6 +913,41 @@ int bio_add_page(struct bio *bio, struct page *page,
 }
 EXPORT_SYMBOL(bio_add_page);
 
+static unsigned convert_to_segs(struct bio* bio, struct page **pages,
+   unsigned char *page_cnt,
+   unsigned nr_pages)
+{
+
+   unsigned idx;
+   unsigned nr_seg = 0;
+   struct request_queue *q = NULL;
+
+   if (bio->bi_disk)
+   q = bio->bi_disk->queue;
+
+   if (!q || !blk_queue_cluster(q)) {
+   memset(page_cnt, 0, nr_pages);
+   return nr_pages;
+   }
+
+   page_cnt[nr_seg] = 0;
+   for (idx = 1; idx < nr_pages; idx++) {
+   struct page *pg_s = pages[nr_seg];
+   struct page *pg = pages[idx];
+
+   if (page_to_pfn(pg_s) + page_cnt[nr_seg] + 1 ==
+   page_to_pfn(pg)) {
+   page_cnt[nr_seg]++;
+   } else {
+   page_cnt[++nr_seg] = 0;
+   if (nr_seg < idx)
+   pages[nr_seg] = pg;
+   }
+   }
+
+   return nr_seg + 1;
+}
+
 /**
  * bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
  * @bio: bio to add pages to
@@ -928,6 +963,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter 
*iter)
struct page **pages = (struct page **)bv;
size_t offset, diff;
ssize_t size;
+   unsigned short nr_segs;
+   unsigned char page_cnt[nr_pages];   /* at most 256 pages */
 
size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, );
if (unlikely(size <= 0))
@@ -943,13 +980,18 @@ int bio_iov_iter_get_pages(struct bio *bio, struct 
iov_iter *iter)
 * need to be reflected here as well.
 */
bio->bi_iter.bi_size += size;
-   bio->bi_vcnt += nr_pages;
-
diff = (nr_pages * PAGE_SIZE - offset) - size;
-   while (nr_pages--) {
-   bv[nr_pages].bv_page = pages[nr_pages];
-   bv[nr_pages].bv_len = PAGE_SIZE;
-   bv[nr_pages].bv_offset = 0;
+
+   /* convert into segments */
+   nr_segs = convert_to_segs(bio, pages, page_cnt, nr_pages);
+   bio->bi_vcnt += nr_segs;
+
+   while (nr_segs--) {
+   unsigned cnt = (unsigned)page_cnt[nr_segs] + 1;
+
+   bv[nr_segs].bv_page = pages[nr_segs];
+   bv[nr_segs].bv_len = PAGE_SIZE * cnt;
+   bv[nr_segs].bv_offset = 0;
}
 
bv[0].bv_offset += offset;
-- 
2.9.5

[RESEND PATCH V5 31/33] block: bio: pass segments to bio if bio_add_page() is bypassed

[Ming Lei]

Under some situations, such as block direct I/O, we can't use
bio_add_page() for merging pages into multipage bvec, so
a new function is implemented for converting page array into one
segment array, then these cases can benefit from multipage bvec
too.

Signed-off-by: Ming Lei 
---
 block/bio.c | 54 --
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index bc3992f52fe8..b7d9089cb28f 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -913,6 +913,41 @@ int bio_add_page(struct bio *bio, struct page *page,
 }
 EXPORT_SYMBOL(bio_add_page);
 
+static unsigned convert_to_segs(struct bio* bio, struct page **pages,
+   unsigned char *page_cnt,
+   unsigned nr_pages)
+{
+
+   unsigned idx;
+   unsigned nr_seg = 0;
+   struct request_queue *q = NULL;
+
+   if (bio->bi_disk)
+   q = bio->bi_disk->queue;
+
+   if (!q || !blk_queue_cluster(q)) {
+   memset(page_cnt, 0, nr_pages);
+   return nr_pages;
+   }
+
+   page_cnt[nr_seg] = 0;
+   for (idx = 1; idx < nr_pages; idx++) {
+   struct page *pg_s = pages[nr_seg];
+   struct page *pg = pages[idx];
+
+   if (page_to_pfn(pg_s) + page_cnt[nr_seg] + 1 ==
+   page_to_pfn(pg)) {
+   page_cnt[nr_seg]++;
+   } else {
+   page_cnt[++nr_seg] = 0;
+   if (nr_seg < idx)
+   pages[nr_seg] = pg;
+   }
+   }
+
+   return nr_seg + 1;
+}
+
 /**
  * bio_iov_iter_get_pages - pin user or kernel pages and add them to a bio
  * @bio: bio to add pages to
@@ -928,6 +963,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter 
*iter)
struct page **pages = (struct page **)bv;
size_t offset, diff;
ssize_t size;
+   unsigned short nr_segs;
+   unsigned char page_cnt[nr_pages];   /* at most 256 pages */
 
size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, );
if (unlikely(size <= 0))
@@ -943,13 +980,18 @@ int bio_iov_iter_get_pages(struct bio *bio, struct 
iov_iter *iter)
 * need to be reflected here as well.
 */
bio->bi_iter.bi_size += size;
-   bio->bi_vcnt += nr_pages;
-
diff = (nr_pages * PAGE_SIZE - offset) - size;
-   while (nr_pages--) {
-   bv[nr_pages].bv_page = pages[nr_pages];
-   bv[nr_pages].bv_len = PAGE_SIZE;
-   bv[nr_pages].bv_offset = 0;
+
+   /* convert into segments */
+   nr_segs = convert_to_segs(bio, pages, page_cnt, nr_pages);
+   bio->bi_vcnt += nr_segs;
+
+   while (nr_segs--) {
+   unsigned cnt = (unsigned)page_cnt[nr_segs] + 1;
+
+   bv[nr_segs].bv_page = pages[nr_segs];
+   bv[nr_segs].bv_len = PAGE_SIZE * cnt;
+   bv[nr_segs].bv_offset = 0;
}
 
bv[0].bv_offset += offset;
-- 
2.9.5