Revert "bio: modify __bio_add_page() to accept pages that don't start a new segment"

This reverts commit 254c4407cb84a6dec90336054615b0f0e996bb7c.

It causes crashes with cryptsetup, even after a few iterations and
updates. Drop it for now.

1 files changed, 23 insertions, 29 deletions

diff --git a/block/bio.c b/block/bio.c
index fb12df9af0fc..0ec61c9e536c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -744,7 +744,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
                                 }
                         }
 
-                        bio->bi_iter.bi_size += len;
                         goto done;
                 }
 
@@ -761,32 +760,29 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
                 return 0;
 
         /*
-         * setup the new entry, we might clear it again later if we
-         * cannot add the page
-         */
-        bvec = &bio->bi_io_vec[bio->bi_vcnt];
-        bvec->bv_page = page;
-        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).
+         * we might lose a segment or two here, but rather that than
+         * make this too complex.
          */
 
-        while (bio->bi_phys_segments > queue_max_segments(q)) {
+        while (bio->bi_phys_segments >= queue_max_segments(q)) {
 
                 if (retried_segments)
-                        goto failed;
+                        return 0;
 
                 retried_segments = 1;
                 blk_recount_segments(q, bio);
         }
 
         /*
+         * setup the new entry, we might clear it again later if we
+         * cannot add the page
+         */
+        bvec = &bio->bi_io_vec[bio->bi_vcnt];
+        bvec->bv_page = page;
+        bvec->bv_len = len;
+        bvec->bv_offset = offset;
+
+        /*
          * if queue has other restrictions (eg varying max sector size
          * depending on offset), it can specify a merge_bvec_fn in the
          * queue to get further control
@@ -803,25 +799,23 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page
                  * merge_bvec_fn() returns number of bytes it can accept
                  * at this offset
                  */
-                if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len)
-                        goto failed;
+                if (q->merge_bvec_fn(q, &bvm, bvec) < bvec->bv_len) {
+                        bvec->bv_page = NULL;
+                        bvec->bv_len = 0;
+                        bvec->bv_offset = 0;
+                        return 0;
+                }
         }
 
         /* If we may be able to merge these biovecs, force a recount */
-        if (bio->bi_vcnt > 1 && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
+        if (bio->bi_vcnt && (BIOVEC_PHYS_MERGEABLE(bvec-1, bvec)))
                 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
 
+        bio->bi_vcnt++;
+        bio->bi_phys_segments++;
  done:
+        bio->bi_iter.bi_size += len;
         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;
 }
 
 /**