[PATCH] mtip32xx: Correctly handle bio->bi_idx != 0 conditions

[PATCH] mtip32xx: Correctly handle bio->bi_idx != 0 conditions

[Sam Bradshaw]

Stacking drivers may append bvecs to existing bio's, resulting
in non-zero bi_idx conditions.  This patch counts the loops of
bio_for_each_segment() rather than inheriting the bi_idx value
to pass as a segment count to the hardware submission routine.

Signed-off-by: Sam Bradshaw <sbradshaw@micron.com>
---
diff --git a/drivers/block/mtip32xx/mtip32xx.c
b/drivers/block/mtip32xx/mtip32xx.c
index 847107e..7c77ae1 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -3863,7 +3863,7 @@ static void mtip_make_request(struct request_queue
*queue, struct bio *bio)
 	struct driver_data *dd = queue->queuedata;
 	struct scatterlist *sg;
 	struct bio_vec *bvec;
-	int nents = 0;
+	int i, nents = 0;
 	int tag = 0, unaligned = 0;

 	if (unlikely(dd->dd_flag & MTIP_DDF_STOP_IO)) {
@@ -3921,11 +3921,12 @@ static void mtip_make_request(struct
request_queue *queue, struct bio *bio)
 		}

 		/* Create the scatter list for this bio. */
-		bio_for_each_segment(bvec, bio, nents) {
+		bio_for_each_segment(bvec, bio, i) {
 			sg_set_page(&sg[nents],
 					bvec->bv_page,
 					bvec->bv_len,
 					bvec->bv_offset);
+			nents++;
 		}

 		/* Issue the read/write. */

Re: [PATCH] mtip32xx: Correctly handle bio->bi_idx != 0 conditions

[Jens Axboe]

On Tue, May 14 2013, Sam Bradshaw wrote:
> 
> Stacking drivers may append bvecs to existing bio's, resulting
> in non-zero bi_idx conditions.  This patch counts the loops of
> bio_for_each_segment() rather than inheriting the bi_idx value
> to pass as a segment count to the hardware submission routine.

Yup, that's a plain bug. Iteration always starts at current index and
forward, so nents wont necessarily start at 0. Applied.

-- 
Jens Axboe