Messages in this thread | | | Date | Sat, 08 Mar 2008 14:33:45 +0900 | From | Yasunori Goto <> | Subject | Re: [PATCH] Fix memory hotplug and bouncing in block layer |
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Oh, thanks for your fixing.
Acked-by: Yasunori Goto <y-goto@jp.fujitsu.com>
> Fix memory hotplug and bouncing in block layer > > Only noticed this while hacking something else, no test case. > > blk_max_low_pfn is initialized once at bootup by the block layer > from max_low_pfn. But max_low_pfn is not necessarily constant > over the runtime of the system when you consider memory hotplug. > What could happen if that someone adds memory later the block > layer wouldn't get updated and then start bouncing memory unnecessarily. > > Also on 64bit blk_max_low_pfn actually isn't needed because > it just disables bouncing essentially and there is no highmem. > And nobody can pass pfns > max_low_pfn to the block layer, > because those wouldn't have a struct page and I suspect > block layer wouldn't be very happy without that. > > So set BLK_BOUNCE_HIGH to infinity (-1ULL) on 64bit. That > avoids the problem of having to update it on memory hotadd. > > On 32bit I kept the same behaviour because at least on i386 > memory hotadd only adds HIGHMEM, never lowmem. > > BLK_BOUNCE_ANY is always set to infinity on both 32 and 64bit. > > Signed-off-by: Andi Kleen <ak@suse.de> > > --- > include/linux/blkdev.h | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > Index: linux/include/linux/blkdev.h > =================================================================== > --- linux.orig/include/linux/blkdev.h > +++ linux/include/linux/blkdev.h > @@ -532,8 +532,13 @@ extern unsigned long blk_max_low_pfn, bl > * BLK_BOUNCE_ANY : don't bounce anything > * BLK_BOUNCE_ISA : bounce pages above ISA DMA boundary > */ > + > +#if BITS_PER_LONG == 32 > #define BLK_BOUNCE_HIGH ((u64)blk_max_low_pfn << PAGE_SHIFT) > -#define BLK_BOUNCE_ANY ((u64)blk_max_pfn << PAGE_SHIFT) > +#else > +#define BLK_BOUNCE_HIGH -1ULL > +#endif > +#define BLK_BOUNCE_ANY (-1ULL) > #define BLK_BOUNCE_ISA (ISA_DMA_THRESHOLD)
-- Yasunori Goto
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