Messages in this thread |  | | From | schwidefsky@de ... | Date | Fri, 17 Nov 2000 17:35:53 +0100 | Subject | Re: Memory management bug |
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>> before I hit yet another BUG in swap_state.c:60. > >The bug in swap_state:60 shows a kernel bug in the VM or random memory >corruption. Make sure you can reproduce on x86 to be sure it's not a s390 >that is randomly corrupting memory. If you read the oops after the BUG message >with asm at hand you will see in the registers the value of page->mapping and >you can guess if it's random memory corruption or bug in VM this way (for >example if `reg & 3 != 0' it's memory corruption for sure, you should also >if it's pointing to a suitable kernel-heap address). I did a little closer investigation. The BUG was triggered by a page with page->mapping pointing to an address space of a mapped ext2 file (page->mapping->a_ops == &ext2_aops). The page had PG_locked, PG_uptodate, PG_active and PG_swap_cache set. The stack backstrace showed that kswapd called do_try_to_free_pages, refill_inactive, swap_out, swap_out_mm, swap_out_vma, try_to_swap_out and add_to_swap_cache where BUG hit. The registers look good, the struct page looks good. I don't think that this was a random memory corruption.
>> Whats the reasoning behind these ifs ? > >To catch memory corruption or things running out of control in the kernel. I was refering to the "if (!order) goto try_again" ifs in alloc_pages, not the "if (something) BUG()" ifs.
blue skies, Martin
Linux/390 Design & Development, IBM Deutschland Entwicklung GmbH Schönaicherstr. 220, D-71032 Böblingen, Telefon: 49 - (0)7031 - 16-2247 E-Mail: schwidefsky@de.ibm.com
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