[2.6.22.2 review 71/84] dm io: fix another panic on large request

[Greg KH <gregkh@suse.de>]

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: Junichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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

--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -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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