block: fix queue bounce limit setting
Impact: don't set GFP_DMA in q->bounce_gfp unnecessarily
All DMA address limits are expressed in terms of the last addressable
unit (byte or page) instead of one plus that. However, when
determining bounce_gfp for 64bit machines in blk_queue_bounce_limit(),
it compares the specified limit against 0x100000000UL to determine
whether it's below 4G ending up falsely setting GFP_DMA in
q->bounce_gfp.
As DMA zone is very small on x86_64, this makes larger SG_IO transfers
very eager to trigger OOM killer. Fix it. While at it, rename the
parameter to @dma_mask for clarity and convert comment to proper
winged style.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 69c42ad..57af728 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -156,26 +156,28 @@
/**
* blk_queue_bounce_limit - set bounce buffer limit for queue
- * @q: the request queue for the device
- * @dma_addr: bus address limit
+ * @q: the request queue for the device
+ * @dma_mask: the maximum address the device can handle
*
* Description:
* Different hardware can have different requirements as to what pages
* it can do I/O directly to. A low level driver can call
* blk_queue_bounce_limit to have lower memory pages allocated as bounce
- * buffers for doing I/O to pages residing above @dma_addr.
+ * buffers for doing I/O to pages residing above @dma_mask.
**/
-void blk_queue_bounce_limit(struct request_queue *q, u64 dma_addr)
+void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
{
- unsigned long b_pfn = dma_addr >> PAGE_SHIFT;
+ unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
int dma = 0;
q->bounce_gfp = GFP_NOIO;
#if BITS_PER_LONG == 64
- /* 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 (b_pfn < (min_t(u64, 0x100000000UL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
+ /*
+ * 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 (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
dma = 1;
q->bounce_pfn = max_low_pfn;
#else
