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SubjectRe: I just got got another Oops
On Thu, 12 Mar 2009 14:31:49 -0400
Gene Heskett <gene.heskett@gmail.com> wrote:

> Mar 12 14:15:02 coyote kernel: [ 2656.832669]
> Mar 12 14:15:02 coyote kernel: [ 2656.832672] Pid: 18877, comm: kmail Not tainted (2.6.29-rc7 #5) System Product Name
> Mar 12 14:15:02 coyote kernel: [ 2656.832675] EIP: 0060:[<c046520b>] EFLAGS: 00210202 CPU: 0
> Mar 12 14:15:02 coyote kernel: [ 2656.832678] EIP is at get_page_from_freelist+0x24b/0x4c0
> Mar 12 14:15:02 coyote kernel: [ 2656.832680] EAX: ffffffff EBX: 80004000 ECX: 00000001 EDX: 00000002
> Mar 12 14:15:02 coyote kernel: [ 2656.832682] ESI: c28fc260 EDI: 00000000 EBP: f2168d5c ESP: f2168cfc
> Mar 12 14:15:02 coyote kernel: [ 2656.832684] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
> Mar 12 14:15:02 coyote kernel: [ 2656.832686] Process kmail (pid: 18877, ti=f2168000 task=f22018b0 task.ti=f2168000)
> Mar 12 14:15:02 coyote kernel: [ 2656.832688] Stack:
> Mar 12 14:15:02 coyote kernel: [ 2656.832689] 00000002 00000044 c28fc060 00000000 f1463ca4 c0744b80 c06d6480 00000002
> Mar 12 14:15:02 coyote kernel: [ 2656.832693] 00000000 00000000 001201d2 00000002 00200246 00000001 c06d6900 00000100
> Mar 12 14:15:02 coyote kernel: [ 2656.832698] 00000000 80000000 c06d7484 c06d6480 c06d6480 c06d6480 f22018b0 00000129

Added linux-mm to CC:

22a9: 8b 1e mov (%esi),%ebx #ebx=80004000 = page->flags
22ab: 89 f2 mov %esi,%edx #remember "page"
22ad: 8b 46 08 mov 0x8(%esi),%eax #esi+8=-1 page->mapcount
22b0: 8b 7e 10 mov 0x10(%esi),%edi #esi+16=0 page->mapping
22b3: f6 c7 40 test $0x40,%bh
22b6: 74 03 je 22bb <get_page_from_freelist+0x24b>
22b8: 8b 56 0c mov 0xc(%esi),%edx #page = page->first_page
22bb: 8b 4a 04 mov 0x4(%edx),%ecx #page->_count

Thank you for disassemble list, from above....
In prep_new_page()
610 static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
611 {
612 if (unlikely(page_mapcount(page) |
613 (page->mapping != NULL) |
614 (page_count(page) != 0) |
615 (page->flags & PAGE_FLAGS_CHECK_AT_PREP)))
616 bad_page(page);
page->mapping = NULL, (VALID)
page->mapcount = -1 (VALID)
page->count ==> NULL access because PageTail() is set, see below.
(Note: from .config, CONFIG_PAGEFLAGS_EXTENDED is set.)

==
288 static inline int page_count(struct page *page)
289 {
290 return atomic_read(&compound_head(page)->_count);
291 }
281 static inline struct page *compound_head(struct page *page)
282 {
283 if (unlikely(PageTail(page)))
284 return page->first_page;
285 return page;
286 }
==
PageTail() is true (this is invalid) and page->first_page contains obsolete data.
But, here, PG_tail should not be there...

Hmm ?

Regards,
-Kame








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