blk-merge: warn if figured out segment number is bigger than nr_phys_segments

[linux-2.6-block.git] / block / blk-merge.c

diff --git a/block/blk-merge.c b/block/blk-merge.c
index de5716d8e525969e7849767a775aabec9e4d8b96..41a55ba0d78e8a97b5707a9194cce3b6ebd1c811 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -76,6 +76,9 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
        struct bio_vec bv, bvprv, *bvprvp = NULL;
        struct bvec_iter iter;
        unsigned seg_size = 0, nsegs = 0, sectors = 0;
+       unsigned front_seg_size = bio->bi_seg_front_size;
+       bool do_split = true;
+       struct bio *new = NULL;
 
        bio_for_each_segment(bv, bio, iter) {
                if (sectors + (bv.bv_len >> 9) > queue_max_sectors(q))
@@ -98,7 +101,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
 
                        seg_size += bv.bv_len;
                        bvprv = bv;
-                       bvprvp = &bv;
+                       bvprvp = &bvprv;
                        sectors += bv.bv_len >> 9;
                        continue;
                }
@@ -108,16 +111,29 @@ new_segment:
 
                nsegs++;
                bvprv = bv;
-               bvprvp = &bv;
+               bvprvp = &bvprv;
                seg_size = bv.bv_len;
                sectors += bv.bv_len >> 9;
+
+               if (nsegs == 1 && seg_size > front_seg_size)
+                       front_seg_size = seg_size;
        }
 
-       *segs = nsegs;
-       return NULL;
+       do_split = false;
 split:
        *segs = nsegs;
-       return bio_split(bio, sectors, GFP_NOIO, bs);
+
+       if (do_split) {
+               new = bio_split(bio, sectors, GFP_NOIO, bs);
+               if (new)
+                       bio = new;
+       }
+
+       bio->bi_seg_front_size = front_seg_size;
+       if (seg_size > bio->bi_seg_back_size)
+               bio->bi_seg_back_size = seg_size;
+
+       return do_split ? new : NULL;
 }
 
 void blk_queue_split(struct request_queue *q, struct bio **bio,
@@ -412,6 +428,12 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
        if (sg)
                sg_mark_end(sg);
 
+       /*
+        * Something must have been wrong if the figured number of
+        * segment is bigger than number of req's physical segments
+        */
+       WARN_ON(nsegs > rq->nr_phys_segments);
+
        return nsegs;
 }
 EXPORT_SYMBOL(blk_rq_map_sg);