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.

diff --git a/block/bio.c b/block/bio.c
index fb12df9..0ec61c9 100644 (file)
--- 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;
                }
 
@@ -761,31 +760,28 @@ 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
@@ -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;
 }
 
 /**