BLOCK: Fix bounce limit address check

This fixes some OOMs on 64bit systems with <4GB of RAM when accessing
the cdrom.

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: Andi Kleen <ak@suse.de>
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index cd995c3fd5d9614d17b913c4d57bcac2beb1670d..1ce88cf8ff91c47897358439524974f220a5b5a4 100644 (file)
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -637,7 +637,7 @@ 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