[PATCH] block: fix the bio_vec array index out-of-bounds test

[Kazuhisa Ichikawa <ki@epsilou.com>]

From: Kazuhisa Ichikawa <ki@epsilou.com>

Current bio_vec array index out-of-bounds test within 
__end_that_request_first() does not seem correct. 
It checks bio->bi_idx against bio->bi_vcnt, but the subsequent code 
uses idx (which is, bio->bi_idx + next_idx) as the array index into 
bio_vec array. This means that the test really make sense only at 
the first iteration of !(nr_bytes >=bio->bi_size) case (when next_idx 
== zero). Fix this by replacing bio->bi_idx with idx.
(This patch applies to 2.6.30-rc4.)

Signed-off-by: Kazuhisa Ichikawa <ki@epsilou.com>
---

--- linux-2.6.30-rc4/block/blk-core.c.ORIG	2009-05-08 00:00:10.000000000 +0900
+++ linux-2.6.30-rc4/block/blk-core.c	2009-05-08 00:00:10.000000000 +0900
@@ -1768,10 +1768,10 @@ static int __end_that_request_first(stru
 		} else {
 			int idx = bio->bi_idx + next_idx;
 
-			if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
+			if (unlikely(idx >= bio->bi_vcnt)) {
 				blk_dump_rq_flags(req, "__end_that");
 				printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
-				       __func__, bio->bi_idx, bio->bi_vcnt);
+				       __func__, idx, bio->bi_vcnt);
 				break;
 			}