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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>
This commit is contained in:
Tejun Heo 2009-04-15 22:10:25 +09:00 committed by Jens Axboe
parent 25636e282f
commit cd0aca2d55
1 changed files with 11 additions and 9 deletions
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20
block/blk-settings.c
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@ -156,26 +156,28 @@ EXPORT_SYMBOL(blk_queue_make_request);
/**
* 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