Messages in this thread | | | Date | Mon, 31 Oct 2005 08:40:23 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH][noop-iosched] don't reuse a freed request |
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On Mon, Oct 31 2005, Arnaldo Carvalho de Melo wrote: > Hi, > > I'm getting the oops below when trying to use qemu with a kernel > built with just the noop iosched, I'm never had looked at this code before, > so I did a quick hack that seems enough for my case. > > Ah, this is with a fairly recent git tree (today), haven't checked > if it is present in 2.6.14. > > Best Regards, > > - Arnaldo > > Unable to handle kernel paging request at virtual address c5f20f60 > printing eip: > c01b0ecd > *pde = 00017067 > *pte = 05f20000 > Oops: 0000 [#1] > DEBUG_PAGEALLOC > Modules linked in: > CPU: 0 > EIP: 0060:[<c01b0ecd>] Not tainted VLI > EFLAGS: 00000046 (2.6.14acme) > EIP is at elv_rq_merge_ok+0x15/0x7b > eax: 00000014 ebx: c5f20f58 ecx: 000003f8 edx: 00000046 > esi: c12a5a90 edi: c5f20f58 ebp: c11658d0 esp: c11658c4 > ds: 007b es: 007b ss: 0068 > Process swapper (pid: 1, threadinfo=c1165000 task=c1164af0) > Stack: c0251883 c5ecfe4c c5d688c0 c1165904 c01b0f48 c5f20f58 c12a5a90 00000000 > c5874000 c018c5e1 c5f15f24 0000002b 00000000 c5ecfe4c c5d688c0 c12a5a90 > c1165920 c01b128d c5f20f58 c12a5a90 000a568a 00000000 00000002 c1165960 > Call Trace: > [<c0102a63>] show_stack+0x78/0x83 > [<c0102b88>] show_registers+0x100/0x167 > [<c0102d35>] die+0xcb/0x140 > [<c0234308>] do_page_fault+0x393/0x53a > [<c0102777>] error_code+0x4f/0x54 > [<c01b0f48>] elv_try_merge+0x15/0x84 > [<c01b128d>] elv_merge+0x1d/0x4f > [<c01b41d9>] __make_request+0xb2/0x425 > [<c01b46f9>] generic_make_request+0x125/0x137
Hrmpf, this looks really bad. Tejun, clearly there are still paths where ->last_rq isn't being cleared.
> --- a/drivers/block/ll_rw_blk.c > +++ b/drivers/block/ll_rw_blk.c > @@ -1787,6 +1787,9 @@ static inline void blk_free_request(requ > if (rq->flags & REQ_ELVPRIV) > elv_put_request(q, rq); > mempool_free(rq, q->rq.rq_pool); > + > + if (rq == q->last_merge) > + q->last_merge = NULL; > } > > static inline struct request *
It's most likely a bug getting this far in the first place, but does it fix things for you? I'll get on this asap.
-- Jens Axboe
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