releases/2.6.28.9/dm-io-respect-bio_max_pages-limit.patch

From d659e6cc98766a1a61d6bdd283f95d149abd7719 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Mon, 16 Mar 2009 17:44:30 +0000
Subject: dm io: respect BIO_MAX_PAGES limit

From: Mikulas Patocka <mpatocka@redhat.com>

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@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 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;