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Subject[patch 14/43] dm io: respect BIO_MAX_PAGES limit
2.6.28-stable review patch.  If anyone has any objections, please let us know.

------------------
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;



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