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Subject[patch v2 1/6] 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>
---
fs/bio.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
Index: linux/fs/bio.c
===================================================================
--- linux.orig/fs/bio.c 2012-03-09 16:56:41.203790008 +0800
+++ linux/fs/bio.c 2012-03-12 10:10:40.696612399 +0800
@@ -1492,7 +1492,7 @@ struct bio_pair *bio_split(struct bio *b
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;
@@ -1502,17 +1502,19 @@ struct bio_pair *bio_split(struct bio *b
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];
- bp->bv2.bv_offset += first_sectors << 9;
- bp->bv2.bv_len -= first_sectors << 9;
- bp->bv1.bv_len = first_sectors << 9;
+ if (bi->bi_vcnt != 0) {
+ bp->bv1 = bi->bi_io_vec[0];
+ bp->bv2 = bi->bi_io_vec[0];
+ 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;


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