From: Shaohua Li <shli@kernel.org>
Date: Fri, 28 Sep 2012 08:38:48 +0000 (+0200)
Subject: block: makes bio_split support bio without data
X-Git-Tag: v3.7-rc1~54^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=02f3939e1a9357b7c370a4a69717cf9c02452737;p=linux.git

block: makes bio_split support bio without data

discard bio hasn't data attached. We hit a BUG_ON with such bio. This makes
bio_split works for such bio.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/bio.c b/fs/bio.c
index f855e0e1869c..9298c65ad9c7 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1475,7 +1475,7 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
 				bi->bi_sector + first_sectors);
 
-	BUG_ON(bi->bi_vcnt != 1);
+	BUG_ON(bi->bi_vcnt != 1 && bi->bi_vcnt != 0);
 	BUG_ON(bi->bi_idx != 0);
 	atomic_set(&bp->cnt, 3);
 	bp->error = 0;
@@ -1485,20 +1485,22 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	bp->bio2.bi_size -= first_sectors << 9;
 	bp->bio1.bi_size = first_sectors << 9;
 
-	bp->bv1 = bi->bi_io_vec[0];
-	bp->bv2 = bi->bi_io_vec[0];
+	if (bi->bi_vcnt != 0) {
+		bp->bv1 = bi->bi_io_vec[0];
+		bp->bv2 = bi->bi_io_vec[0];
 
-	if (bio_is_rw(bi)) {
-		bp->bv2.bv_offset += first_sectors << 9;
-		bp->bv2.bv_len -= first_sectors << 9;
-		bp->bv1.bv_len = first_sectors << 9;
-	}
+		if (bio_is_rw(bi)) {
+			bp->bv2.bv_offset += first_sectors << 9;
+			bp->bv2.bv_len -= first_sectors << 9;
+			bp->bv1.bv_len = first_sectors << 9;
+		}
 
-	bp->bio1.bi_io_vec = &bp->bv1;
-	bp->bio2.bi_io_vec = &bp->bv2;
+		bp->bio1.bi_io_vec = &bp->bv1;
+		bp->bio2.bi_io_vec = &bp->bv2;
 
-	bp->bio1.bi_max_vecs = 1;
-	bp->bio2.bi_max_vecs = 1;
+		bp->bio1.bi_max_vecs = 1;
+		bp->bio2.bi_max_vecs = 1;
+	}
 
 	bp->bio1.bi_end_io = bio_pair_end_1;
 	bp->bio2.bi_end_io = bio_pair_end_2;