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Subject[patch] bigmem fix for random out of memory (for 2.3.25)
Leonard spotted a bug in the bigmem initialization code. I couldn't debug
it as it can't trigger with the bigmem emulation.

Actually GFP will return NULL if RMQUEUE grabbed the physical page at
address -PAGE_OFFSET. Lenonard fixed this to just avoid to put the
bigmem in the freelist and I would do the same too as one page is not a
big deal with real bigmem hardware.

I merged his plain fix in my 2.2.13 bigmem and I reworked it for 2.3.25.

The other cleaner way to fix this bug is to change GFP to return a `struct
page *' or the `pfn' and the other way is definitely not a one-liner ;).
Even if we want to fix it properly in the other way we can go with this
trick today (it will be trivial to remove the check later).

--- 2.3.25-i386/arch/i386/mm/init.c.~1~ Tue Oct 26 21:30:50 1999
+++ 2.3.25-i386/arch/i386/mm/init.c Wed Nov 3 16:52:30 1999
@@ -526,6 +526,12 @@
SetPageReserved(page);
continue;
}
+ /* GFP in page_alloc.c would return zero for the
+ bigmem page located at physical address -PAGE_OFFSET.
+ We cannot allow GFP to return 0 since the callers of
+ treat 0 as an allocation failure. */
+ if (!((tmp << PAGE_SHIFT) + PAGE_OFFSET))
+ continue;
ClearPageReserved(page);
set_bit(PG_highmem, &page->flags);
atomic_set(&page->count, 1);
Andrea


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