[PATCH v3 31/49] block: deal with dirtying pages for multipage bvec

[Ming Lei]

In bio_check_pages_dirty(), bvec->bv_page is used as flag
for marking if the page has been dirtied & released, and if
no, it will be dirtied in deferred workqueue.

With multipage bvec, we can't do that any more, so change
the logic into checking all pages in one mp bvec, and only
release all these pages if all are dirtied, otherwise dirty
them all in deferred wrokqueue.

Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
 block/bio.c | 45 +++++++++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 8 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 28697e3c8ce3..716e6917b0fd 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1650,8 +1650,9 @@ void bio_set_pages_dirty(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	int i;
+	struct bvec_iter_all bia;
 
-	bio_for_each_segment_all(bvec, bio, i) {
+	bio_for_each_segment_all_sp(bvec, bio, i, bia) {
 		struct page *page = bvec->bv_page;
 
 		if (page && !PageCompound(page))
@@ -1659,16 +1660,26 @@ void bio_set_pages_dirty(struct bio *bio)
 	}
 }
 
+static inline void release_mp_bvec_pages(struct bio_vec *bvec)
+{
+	struct bio_vec bv;
+	struct bvec_iter iter;
+
+	bvec_for_each_sp_bvec(bv, bvec, iter)
+		put_page(bv.bv_page);
+}
+
 static void bio_release_pages(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	int i;
 
-	bio_for_each_segment_all(bvec, bio, i) {
+	/* iterate each mp bvec */
+	bio_for_each_segment_all_mp(bvec, bio, i) {
 		struct page *page = bvec->bv_page;
 
 		if (page)
-			put_page(page);
+			release_mp_bvec_pages(bvec);
 	}
 }
 
@@ -1712,20 +1723,38 @@ static void bio_dirty_fn(struct work_struct *work)
 	}
 }
 
+static inline void check_mp_bvec_pages(struct bio_vec *bvec,
+		int *nr_dirty, int *nr_pages)
+{
+	struct bio_vec bv;
+	struct bvec_iter iter;
+
+	bvec_for_each_sp_bvec(bv, bvec, iter) {
+		struct page *page = bv.bv_page;
+
+		if (PageDirty(page) || PageCompound(page))
+			(*nr_dirty)++;
+		(*nr_pages)++;
+	}
+}
+
 void bio_check_pages_dirty(struct bio *bio)
 {
 	struct bio_vec *bvec;
 	int nr_clean_pages = 0;
 	int i;
 
-	bio_for_each_segment_all(bvec, bio, i) {
-		struct page *page = bvec->bv_page;
+	bio_for_each_segment_all_mp(bvec, bio, i) {
+		int nr_dirty = 0, nr_pages = 0;
+
+		check_mp_bvec_pages(bvec, &nr_dirty, &nr_pages);
 
-		if (PageDirty(page) || PageCompound(page)) {
-			put_page(page);
+		/* release all pages in the mp bvec if all are dirtied */
+		if (nr_dirty == nr_pages) {
+			release_mp_bvec_pages(bvec);
 			bvec->bv_page = NULL;
 		} else {
-			nr_clean_pages++;
+			nr_clean_pages += nr_pages;
 		}
 	}
 
-- 
2.9.4