[PATCH 3/4] xen-blkback: check the number of iovecs before allocating a bios

[Roger Pau Monne <roger.pau@citrix.com>]

With the introduction of indirect segments we can receive requests
with a number of segments bigger than the maximum number of allowed
iovecs in a bios, so make sure that blkback doesn't try to allocate a
bios with more iovecs than BIO_MAX_PAGES

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/block/xen-blkback/blkback.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index d622d86..876116b 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1236,7 +1236,8 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 				     seg[i].nsec << 9,
 				     seg[i].offset) == 0)) {
 
-			bio = bio_alloc(GFP_KERNEL, nseg-i);
+			int nr_iovecs = (nseg-i) > BIO_MAX_PAGES ? BIO_MAX_PAGES : (nseg-i);
+			bio = bio_alloc(GFP_KERNEL, nr_iovecs);
 			if (unlikely(bio == NULL))
 				goto fail_put_bio;
 
-- 
1.7.7.5 (Apple Git-26)