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[PATCH] block: disable block layer bouncing for most memory on 64bit systems

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The low level PCI DMA mapping functions should handle it in most cases.

This should fix problems with depleting the DMA zone early. The old
code used precious GFP_DMA memory in many cases where it was not needed.

Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen 2006-03-08 17:57:26 -08:00 committed by Linus Torvalds
parent f9262c12c0
commit 5ee1af9f51
1 changed files with 18 additions and 13 deletions
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31
block/ll_rw_blk.c
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@ -625,26 +625,31 @@ static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
* 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 @page. By default
* the block layer sets this to the highest numbered "low" memory page.
* buffers for doing I/O to pages residing above @page.
**/
void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
{
unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
int dma = 0;
/*
* set appropriate bounce gfp mask -- unfortunately we don't have a
* full 4GB zone, so we have to resort to low memory for any bounces.
* ISA has its own < 16MB zone.
*/
if (bounce_pfn < blk_max_low_pfn) {
BUG_ON(dma_addr < BLK_BOUNCE_ISA);
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 (bounce_pfn < (0xffffffff>>PAGE_SHIFT))
dma = 1;
q->bounce_pfn = max_low_pfn;
#else
if (bounce_pfn < blk_max_low_pfn)
dma = 1;
q->bounce_pfn = bounce_pfn;
#endif
if (dma) {
init_emergency_isa_pool();
q->bounce_gfp = GFP_NOIO | GFP_DMA;
} else
q->bounce_gfp = GFP_NOIO;
q->bounce_pfn = bounce_pfn;
q->bounce_pfn = bounce_pfn;
}
}
EXPORT_SYMBOL(blk_queue_bounce_limit);