[patch 13/32] dm io: respect BIO_MAX_PAGES limit

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

commit d659e6cc98766a1a61d6bdd283f95d149abd7719 upstream.

dm-io calls bio_get_nr_vecs to get the maximum number of pages to use
for a given device.  It allocates one additional bio_vec to use
internally but failed to respect BIO_MAX_PAGES, so fix this.

This was the likely cause of:
  https://bugzilla.redhat.com/show_bug.cgi?id=173153

Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/md/dm-io.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -292,6 +292,8 @@ static void do_region(int rw, unsigned r
 					     (PAGE_SIZE >> SECTOR_SHIFT));
 		num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
 				      num_bvecs);
+		if (unlikely(num_bvecs > BIO_MAX_PAGES))
+			num_bvecs = BIO_MAX_PAGES;
 		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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