1 files changed, 31 insertions, 29 deletions

diff --git a/block/bio.c b/block/bio.c
index 26853e072cd7..8d516d508ae3 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -665,6 +665,27 @@ static inline bool page_is_mergeable(const struct bio_vec *bv,
         return true;
 }
 
+/*
+ * Check if the @page can be added to the current segment(@bv), and make
+ * sure to call it only if page_is_mergeable(@bv, @page) is true
+ */
+static bool can_add_page_to_seg(struct request_queue *q,
+                struct bio_vec *bv, struct page *page, unsigned len,
+                unsigned offset)
+{
+        unsigned long mask = queue_segment_boundary(q);
+        phys_addr_t addr1 = page_to_phys(bv->bv_page) + bv->bv_offset;
+        phys_addr_t addr2 = page_to_phys(page) + offset + len - 1;
+
+        if ((addr1 | mask) != (addr2 | mask))
+                return false;
+
+        if (bv->bv_len + len > queue_max_segment_size(q))
+                return false;
+
+        return true;
+}
+
 /**
  *      __bio_add_pc_page       - attempt to add page to passthrough bio
  *      @q: the target queue
@@ -685,7 +706,6 @@ int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
                 struct page *page, unsigned int len, unsigned int offset,
                 bool put_same_page)
 {
-        int retried_segments = 0;
         struct bio_vec *bvec;
 
         /*
@@ -709,6 +729,7 @@ int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
                     offset == bvec->bv_offset + bvec->bv_len) {
                         if (put_same_page)
                                 put_page(page);
+ bvec_merge:
                         bvec->bv_len += len;
                         bio->bi_iter.bi_size += len;
                         goto done;
@@ -720,11 +741,18 @@ int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
                  */
                 if (bvec_gap_to_prev(q, bvec, offset))
                         return 0;
+
+                if (page_is_mergeable(bvec, page, len, offset, false) &&
+                                can_add_page_to_seg(q, bvec, page, len, offset))
+                        goto bvec_merge;
         }
 
         if (bio_full(bio))
                 return 0;
 
+        if (bio->bi_phys_segments >= queue_max_segments(q))
+                return 0;
+
         /*
          * setup the new entry, we might clear it again later if we
          * cannot add the page
@@ -734,38 +762,12 @@ int __bio_add_pc_page(struct request_queue *q, struct bio *bio,
         bvec->bv_len = len;
         bvec->bv_offset = offset;
         bio->bi_vcnt++;
-        bio->bi_phys_segments++;
         bio->bi_iter.bi_size += len;
 
-        /*
-         * Perform a recount if the number of segments is greater
-         * than queue_max_segments(q).
-         */
-
-        while (bio->bi_phys_segments > queue_max_segments(q)) {
-
-                if (retried_segments)
-                        goto failed;
-
-                retried_segments = 1;
-                blk_recount_segments(q, bio);
-        }
-
-        /* If we may be able to merge these biovecs, force a recount */
-        if (bio->bi_vcnt > 1 && biovec_phys_mergeable(q, bvec - 1, bvec))
-                bio_clear_flag(bio, BIO_SEG_VALID);
-
  done:
+        bio->bi_phys_segments = bio->bi_vcnt;
+        bio_set_flag(bio, BIO_SEG_VALID);
         return len;
-
- failed:
-        bvec->bv_page = NULL;
-        bvec->bv_len = 0;
-        bvec->bv_offset = 0;
-        bio->bi_vcnt--;
-        bio->bi_iter.bi_size -= len;
-        blk_recount_segments(q, bio);
-        return 0;
 }
 EXPORT_SYMBOL(__bio_add_pc_page);