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

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);