From: Coywolf Qi Hunt <coywolf@greatcn.org>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org
Subject: [BUG FIX] [ARM/ARM26] find_memend_and_nodes bug fix
Date: Wed, 30 Jun 2004 17:56:18 +0800 [thread overview]
Message-ID: <40E28E42.3030408@greatcn.org> (raw)
In-Reply-To: <20040629115830.A24951@flint.arm.linux.org.uk>
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.
=======================================================================
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
next prev parent reply other threads:[~2004-06-30 9:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-28 15:55 [BUG FIX] [PATCH] fork_init() max_low_pfn fixes potential OOM bug on big highmem machine Coywolf Qi Hunt
2004-06-28 16:53 ` Russell King
2004-06-29 10:48 ` Coywolf Qi Hunt
2004-06-29 10:58 ` Russell King
2004-06-30 9:56 ` Coywolf Qi Hunt [this message]
2004-06-29 11:11 ` Chris Wedgwood
2004-06-30 10:43 ` [BUG FIX] fork_init() " Coywolf Qi Hunt
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