Messages in this thread | | | Date | Mon, 14 Jan 2002 08:24:35 +0100 | From | Jens Axboe <> | Subject | Re: Q: blk_queue_bounce_limit |
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On Sun, Jan 13 2002, Manfred Spraul wrote: > I think the selection of the ISA pool in blk_queue_bounce_limit is > wrong: > it switches to the ISA pool if the requested DMA address is equal to > 16 MB. I think it must switch if the requested bounce limit is smaller > than max_low_pfn. > > <<<<<<< > - if (dma_addr == BLK_BOUNCE_ISA) { > + if (bounce_pfn < blk_max_low_pfn) { > + BUG_ON(dma_addr < BLK_BOUNCE_ISA); > init_emergency_isa_pool(); > q->bounce_gfp = GFP_NOIO | GFP_DMA; > } else > q->bounce_gfp = GFP_NOHIGHIO; > <<< > > Usually both lines are identical, except: > - If only 16 MB are installed, then bouncing to ISA is never needed. > - There could be broken devices that only support DMA to < 512 MB. > For such a device no bounce it needed if less than 512 MB is installed, > and if more is installed we must bounce to ISA. (since we don't have > a 512MB zone). > - Bouncing to less that 16 MB is not supported.
Yes it's a grey area, I'll add your patch.
-- Jens Axboe
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