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SubjectRe: [bug?] bio: add experimental support for inlining a number of bio_vecs inside the bio
On Wed, Dec 10 2008, KOSAKI Motohiro wrote:
> CC to Jens Axboe
>
> > message
> > ==================================
> > Creating root device.
> > Unable to handle kernel NULL pointer dereference (address 00000000000000c8)
> > swapper[0]: Oops 8813272891392 [1]
> > Modules linked in: dm_snapshot dm_zero dm_mirror dm_region_hash dm_log dm_mod lpfc mptspi mptscsih mptbase ehci_hcd ohci_hcd uhci_hcd usbcore
> >
> > Pid: 0, CPU 0, comm: swapper
> > psr : 0000101008026018 ifs : 800000000000038a ip : [<a00000010032be00>] Not tainted (2.6.28-rc7-next-20081210)
> > ip is at __blk_complete_request+0x20/0x2a0
> > unat: 0000000000000000 pfs : 0000000000000205 rsc : 0000000000000003
> > rnat: 000000000000000c bsps: e000000001143180 pr : 656960155aa55695
> > ldrs: 0000000000000000 ccv : 0000000000000000 fpsr: 0009804c0270033f
> > csd : 0000000000000000 ssd : 0000000000000000
> > b0 : a00000010032c0e0 b6 : a000000100364480 b7 : a000000100504600
> > f6 : 0fffcfffffffff0000000 f7 : 0ffe6e830000000000000
> > f8 : 1000ae830000000000000 f9 : 1003e0000000000004020
> > f10 : 1003e0000000000000060 f11 : 1003e00000000000000ab
> > r1 : a000000100ef6c30 r2 : 00000000000000c8 r3 : e0000040c2611fe0
> > r8 : 0000000000000000 r9 : 0000000000000801 r10 : 0000000000000a01
> > r11 : 0000000000000801 r12 : a000000100b2fb40 r13 : a000000100b20000
> > r14 : 0000000000000000 r15 : 0000000000000000 r16 : 0000000000000001
> > r17 : e0000040c2611ff0 r18 : 0000000000000200 r19 : e0000040c3100000
> > r20 : a040000000000000 r21 : 000000000000000e r22 : a000000100504600
> > r23 : e0000040c0722a90 r24 : a000000100b2fbd0 r25 : a000000100ba3908
> > r26 : 0000000000000400 r27 : 00000000000000ff r28 : 0000000000000000
> > r29 : a000000100b20d34 r30 : 000000000000000d r31 : 0000000000007fff
> >
> > Call Trace:
> > [<a000000100017940>] show_stack+0x80/0xa0
> > sp=a000000100b2f710 bsp=a000000100b21358
> > [<a000000100018240>] show_regs+0x880/0x8c0
> > sp=a000000100b2f8e0 bsp=a000000100b21300
> > [<a000000100040570>] die+0x1b0/0x2e0
> > sp=a000000100b2f8e0 bsp=a000000100b212b8
> > [<a000000100773dd0>] ia64_do_page_fault+0x810/0xb00
> > sp=a000000100b2f8e0 bsp=a000000100b21258
> > [<a00000010000c860>] ia64_native_leave_kernel+0x0/0x270
> > sp=a000000100b2f970 bsp=a000000100b21258
> > [<a00000010032be00>] __blk_complete_request+0x20/0x2a0
> > sp=a000000100b2fb40 bsp=a000000100b21208
> > [<a00000010032c0e0>] blk_complete_request+0x60/0x80
> > sp=a000000100b2fb40 bsp=a000000100b211e0
> > [<a000000100504620>] scsi_done+0x20/0x40
> > sp=a000000100b2fb40 bsp=a000000100b211c0
> > [<a000000201b12160>] mptscsih_io_done+0x7c0/0xf40 [mptscsih]
> > sp=a000000100b2fb40 bsp=a000000100b210f8
> > [<a000000201a480f0>] mpt_interrupt+0x1f0/0x1280 [mptbase]
> > sp=a000000100b2fb40 bsp=a000000100b21098
> > [<a0000001001211a0>] handle_IRQ_event+0x80/0x120
> > sp=a000000100b2fbb0 bsp=a000000100b21060
> > [<a000000100121570>] __do_IRQ+0x330/0x440
> > sp=a000000100b2fbb0 bsp=a000000100b21000
> > [<a000000100014990>] ia64_handle_irq+0x410/0x440
> > sp=a000000100b2fbb0 bsp=a000000100b20f78
> > [<a00000010000c860>] ia64_native_leave_kernel+0x0/0x270
> > sp=a000000100b2fbb0 bsp=a000000100b20f78
> > [<a0000001000186e0>] default_idle+0x1a0/0x1c0
> > sp=a000000100b2fd80 bsp=a000000100b20f10
> > [<a0000001000175a0>] cpu_idle+0x1e0/0x3c0
> > sp=a000000100b2fe20 bsp=a000000100b20eb0
> > [<a000000100733c50>] rest_init+0xd0/0x100
> > sp=a000000100b2fe20 bsp=a000000100b20e98
> > [<a000000100971440>] start_kernel+0x740/0x800
> > sp=a000000100b2fe20 bsp=a000000100b20e20
> > [<a000000100777e00>] __kprobes_text_end+0x760/0x780
> > sp=a000000100b2fe30 bsp=a000000100b20d80
> > Kernel panic - not syncing: Aiee, killing interrupt handler!
>
> bisect information is here.
>
>
> % git bisect log
> git bisect start
> # bad: [87602124ea74da54ae39e713a28d5593af9ad5ef] Add linux-next specific files for 20081210
> git bisect bad 87602124ea74da54ae39e713a28d5593af9ad5ef
> # good: [061e41fdb5047b1fb161e89664057835935ca1d2] Linux 2.6.28-rc7
> git bisect good 061e41fdb5047b1fb161e89664057835935ca1d2
> # good: [9be550f4dabca95e3b6d02a6865b58bfdf255902] Merge commit 'kvm/master'
> git bisect good 9be550f4dabca95e3b6d02a6865b58bfdf255902
> # good: [472ec6db8c6ca2d6088b7ebff6fa3210b9f9726c] Merge commit 'net/master'
> git bisect good 472ec6db8c6ca2d6088b7ebff6fa3210b9f9726c
> # good: [359ec37f233829f8765e41fb7dcb79f5b24a20db] Merge commit 'gfs2/master'
> git bisect good 359ec37f233829f8765e41fb7dcb79f5b24a20db
> # bad: [17ed6c92c143ff0b5d5eaac9fadd258cc4e8252b] Merge commit 'voltage/for-next'
> git bisect bad 17ed6c92c143ff0b5d5eaac9fadd258cc4e8252b
> # bad: [678ac94e1e49ba2094d43cf3a9ffa0fff78457d1] Merge commit 'slab/for-next'
> git bisect bad 678ac94e1e49ba2094d43cf3a9ffa0fff78457d1
> # bad: [da9849d8bc82d8764f3ada875764f64714d8b018] Merge commit 'firmware/master'
> git bisect bad da9849d8bc82d8764f3ada875764f64714d8b018
> # bad: [ecf323abe734650adb0790fa681490b288fc9073] block: use min_not_zero in blk_queue_stack_limits
> git bisect bad ecf323abe734650adb0790fa681490b288fc9073
> # good: [834ec249cbbefc4121964d5e843ac02ecc253d39] block: reorder struct bio to remove padding on 64bit
> git bisect good 834ec249cbbefc4121964d5e843ac02ecc253d39
> # good: [520e832e193f61001dc5d35d9536850713880630] bio: only mempool back the largest bio_vec slab cache
> git bisect good 520e832e193f61001dc5d35d9536850713880630
> # bad: [102e8207838eabe09a4275f97a03334fa8609aa0] aio: make the lookup_ioctx() lockless
> git bisect bad 102e8207838eabe09a4275f97a03334fa8609aa0
> # good: [dc23b3285aaaa0dbd013bcfacad26f752e23927e] bio: allow individual slabs in the bio_set
> git bisect good dc23b3285aaaa0dbd013bcfacad26f752e23927e
> # bad: [30e62ce1ce96ff01d4826b0e476941169c94041d] bio: add experimental support for inlining a number of bio_vecs inside the bio
> git bisect bad 30e62ce1ce96ff01d4826b0e476941169c94041d
>
>
>
> ---------------------
> commit 30e62ce1ce96ff01d4826b0e476941169c94041d
> Author: Jens Axboe <jens.axboe@oracle.com>
> Date: Fri Dec 5 13:58:19 2008 +0100
>
> bio: add experimental support for inlining a number of bio_vecs inside the bio
>
> When we go and allocate a bio for IO, we actually do two allocations.
> One for the bio itself, and one for the bi_io_vec that holds the
> actual pages we are interested in.
>
> This feature inlines a definable amount of io vecs inside the bio
> itself, so we eliminate the bio_vec array allocation for IO's up
> to a certain size. It defaults to 4 vecs, which is typically 16k
> of IO.
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
>
> ------------------------
>
>
> experimental??

Experimental in the sense that it's the first version, not the concept.
It's held up well for me, but just yesterday I received the first bug
report on a ppc platform and now you have this on ia64. Can you pin
point where in __blk_complete_request() it dies with the NULL pointer
deref? I'm assuming you don't have CONFIG_FAIL_IO_TIMEOUT set, otherwise
I don't see how it could fail. So that looks like req->q being NULL,
which doesn't have much relation to this.

Can you try with slab and pagealloc debugging options switched on? The
above looks like a side effect of some badness there.

--
Jens Axboe



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