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Subject[2.6.23 PATCH 07/18] dm io: fix panic on large request
From: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>

bio_alloc_bioset() will return NULL if 'num_vecs' is too large.
Use bio_get_nr_vecs() to get estimation of maximum number.

Signed-off-by: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

---
drivers/md/dm-io.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletion(-)

Index: linux/drivers/md/dm-io.c
===================================================================
--- linux.orig/drivers/md/dm-io.c 2007-07-11 21:37:32.000000000 +0100
+++ linux/drivers/md/dm-io.c 2007-07-11 21:37:43.000000000 +0100
@@ -293,7 +293,10 @@ static void do_region(int rw, unsigned i
* bvec for bio_get/set_region() and decrement bi_max_vecs
* to hide it from bio_add_page().
*/
- num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;
+ num_bvecs = dm_sector_div_up(remaining,
+ (PAGE_SIZE >> SECTOR_SHIFT));
+ num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
+ num_bvecs);
bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
bio->bi_sector = where->sector + (where->count - remaining);
bio->bi_bdev = where->bdev;
-
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