[BLOCK] Fix bounce limit address check

Do a safer check for when to enable DMA. Currently we enable ISA DMA
for cases that do not need it, resulting in OOM conditions when ZONE_DMA
runs out of space.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 2270bb451385..0603ab2f3692 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -638,7 +638,7 @@ void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
         /* Assume anything <= 4GB can be handled by IOMMU.
            Actually some IOMMUs can handle everything, but I don't
            know of a way to test this here. */
-        if (bounce_pfn < (0xffffffff>>PAGE_SHIFT))
+        if (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
                 dma = 1;
         q->bounce_pfn = max_low_pfn;
 #else