Messages in this thread Patch in this message | | | Date | Wed, 30 Jun 2004 17:56:18 +0800 | From | Coywolf Qi Hunt <> | Subject | [BUG FIX] [ARM/ARM26] find_memend_and_nodes bug fix |
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Russell King wrote:
>On Tue, Jun 29, 2004 at 06:48:14PM +0800, Coywolf Qi Hunt wrote: > > >>Russell King wrote: >>Actually there's physical DRAM offset: PHY_OFFSET, defined on ARM only. >>max_low_pfn happens to be the same as `num_lowpages'. >>These assignments seems illogical in naming. But just happen to let this >>patch work. Other platforms may still break. >> >> > >That may be a bug actually. Looking at ll_rw_blk.c: > > unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT; > if (bounce_pfn < blk_max_low_pfn) { > > blk_max_low_pfn = max_low_pfn; > >dma_addr are physical addresses, so bounce_pfn is referenced to a PFN0 >equal to physical address 0. This implies that blk_max_low_pfn is >likewise, as is max_low_pfn. > > > >>[coywolf@everest ~/linux-2.6.7/arch]$ grep max_low_pfn arm* -rn >>arm/mm/init.c:235: max_low_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET); >> >> > >However, here, max_low_pfn of zero corresponds with the PFN of >PHYS_OFFSET. We have something with two different origins being >compared, which is nonsense. So something is wrong somewhere, >and my money is on max_low_pfn. > > > The bug may get into panic when there's still enough memory for block i/o. Here's the patch with also a BUG_ON improvement.
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diff -Nrup linux-2.6.7/arch/arm/mm/init.c linux-2.6.7-cy2/arch/arm/mm/init.c --- linux-2.6.7/arch/arm/mm/init.c 2004-06-29 23:03:30.000000000 -0500 +++ linux-2.6.7-cy2/arch/arm/mm/init.c 2004-06-30 04:32:42.215999091 -0500 @@ -231,9 +231,10 @@ find_memend_and_nodes(struct meminfo *mi * This doesn't seem to be used by the Linux memory * manager any more. If we can get rid of it, we * also get rid of some of the stuff above as well. + * + * blk_max_low_pfn depends on this. -- coywolf */ - max_low_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET); - max_pfn = memend_pfn - O_PFN_DOWN(PHYS_OFFSET); + max_low_pfn = max_pfn = memend_pfn; return bootmem_pages; } diff -Nrup linux-2.6.7/arch/arm26/mm/init.c linux-2.6.7-cy2/arch/arm26/mm/init.c --- linux-2.6.7/arch/arm26/mm/init.c 2004-05-09 21:33:20.000000000 -0500 +++ linux-2.6.7-cy2/arch/arm26/mm/init.c 2004-06-30 03:59:51.000000000 -0500 @@ -160,9 +160,7 @@ find_memend_and_nodes(struct meminfo *mi np->bootmap_pages = 0; - if (mi->bank->size == 0) { - BUG(); - } + BUG_ON(mi->bank->size == 0) /* * Get the start and end pfns for this bank @@ -183,9 +181,10 @@ find_memend_and_nodes(struct meminfo *mi * This doesn't seem to be used by the Linux memory * manager any more. If we can get rid of it, we * also get rid of some of the stuff above as well. + * + * blk_max_low_pfn depends on this. -- coywolf */ - max_low_pfn = memend_pfn - PFN_DOWN(PHYS_OFFSET); - max_pfn = memend_pfn - PFN_DOWN(PHYS_OFFSET); + max_low_pfn = max_pfn = memend_pfn; mi->end = memend_pfn << PAGE_SHIFT; } --
Coywolf Qi Hunt Admin of http://GreatCN.org and http://LoveCN.org
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