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Subject: Re: [PATCH BUGFIX 1/1] block, bfq: add requeue-request hook
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <BE442D49-D280-4B35-89ED-43C729263F2A@linaro.org>
Date:   Tue, 6 Feb 2018 13:40:40 +0100
Cc:     Mike Galbraith <efault@gmx.de>,
        Oleksandr Natalenko <oleksandr@natalenko.name>,
        Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Alban Browaeys <alban.browaeys@gmail.com>, ming.lei@redhat.com,
        ivan@ludios.org, 169364@studenti.unimore.it,
        Serena Ziviani <ziviani.serena@gmail.com>
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> Il giorno 06 feb 2018, alle ore 13:26, Paolo Valente =
<paolo.valente@linaro.org> ha scritto:
>=20
>=20
>=20
>> Il giorno 06 feb 2018, alle ore 12:57, Mike Galbraith <efault@gmx.de> =
ha scritto:
>>=20
>> On Tue, 2018-02-06 at 10:38 +0100, Paolo Valente wrote:
>>>=20
>>> Hi Mike,
>>> as you can imagine, I didn't get any failure in my pre-submission
>>> tests on this patch.  In addition, it is not that easy to link this
>>> patch, which just adds some internal bfq housekeeping in case of a
>>> requeue, with a corruption of external lists for general I/O
>>> management.
>>>=20
>>> In this respect, as Oleksandr comments point out, by switching from
>>> cfq to bfq, you switch between much more than two schedulers.  =
Anyway,
>>> who knows ...
>>=20
>> Not me.  Box seems to be fairly sure that it is bfq.
>=20
> Yeah, sorry for the too short comment: what I meant is that cfq (and
> deadline) are in legacy blk, while bfq is in blk-mq.  So, to use bfq,
> you must also switch from legacy-blk I/O stack to blk-mq I/O stack.
>=20
>=20
>> Twice again box
>> went belly up on me in fairly short order with bfq, but seemed fine
>> with deadline.  I'm currently running deadline again, and box again
>> seems solid, thought I won't say _is_ solid until it's been happily
>> trundling along with deadline for a quite a bit longer.
>>=20
>=20
> As Oleksadr asked too, is it deadline or mq-deadline?
>=20
>> I was ssh'd in during the last episode, got this out.  I should be
>> getting crash dumps, but seems kdump is only working intermittently
>> atm.  I did get one earlier, but 3 of 4 times not.  Hohum.
>>=20
>> [  484.179292] BUG: unable to handle kernel paging request at =
ffffffffa0817000
>> [  484.179436] IP: __trace_note_message+0x1f/0xd0
>> [  484.179576] PGD 1e0c067 P4D 1e0c067 PUD 1e0d063 PMD 3faff2067 PTE =
0
>> [  484.179719] Oops: 0000 [#1] SMP PTI
>> [  484.179861] Dumping ftrace buffer:
>> [  484.180011]    (ftrace buffer empty)
>> [  484.180138] Modules linked in: fuse(E) ebtable_filter(E) =
ebtables(E) af_packet(E) bridge(E) stp(E) llc(E) iscsi_ibft(E) =
iscsi_boot_sysfs(E) nf_conntrack_ipv6(E) nf_defrag_ipv6(E) ipt_REJECT(E) =
xt_tcpudp(E) iptable_filter(E) ip6table_mangle(E) =
nf_conntrack_netbios_ns(E) nf_conntrack_broadcast(E) =
nf_conntrack_ipv4(E) nf_defrag_ipv4(E) ip_tables(E) xt_conntrack(E) =
nf_conntrack(E) ip6table_filter(E) ip6_tables(E) x_tables(E) =
nls_iso8859_1(E) nls_cp437(E) intel_rapl(E) x86_pkg_temp_thermal(E) =
intel_powerclamp(E) snd_hda_codec_hdmi(E) coretemp(E) kvm_intel(E) =
snd_hda_codec_realtek(E) kvm(E) snd_hda_codec_generic(E) =
snd_hda_intel(E) snd_hda_codec(E) sr_mod(E) snd_hwdep(E) cdrom(E) =
joydev(E) snd_hda_core(E) snd_pcm(E) snd_timer(E) irqbypass(E) snd(E) =
crct10dif_pclmul(E) crc32_pclmul(E) crc32c_intel(E) r8169(E)
>> [  484.180740]  iTCO_wdt(E) ghash_clmulni_intel(E) mii(E) =
iTCO_vendor_support(E) pcbc(E) aesni_intel(E) soundcore(E) aes_x86_64(E) =
shpchp(E) crypto_simd(E) lpc_ich(E) glue_helper(E) i2c_i801(E) mei_me(E) =
mfd_core(E) mei(E) cryptd(E) intel_smartconnect(E) pcspkr(E) fan(E) =
thermal(E) nfsd(E) auth_rpcgss(E) nfs_acl(E) lockd(E) grace(E) sunrpc(E) =
hid_logitech_hidpp(E) hid_logitech_dj(E) uas(E) usb_storage(E) =
hid_generic(E) usbhid(E) nouveau(E) wmi(E) i2c_algo_bit(E) =
drm_kms_helper(E) syscopyarea(E) sysfillrect(E) sysimgblt(E) =
fb_sys_fops(E) ahci(E) xhci_pci(E) ehci_pci(E) libahci(E) ttm(E) =
ehci_hcd(E) xhci_hcd(E) libata(E) drm(E) usbcore(E) video(E) button(E) =
sd_mod(E) vfat(E) fat(E) virtio_blk(E) virtio_mmio(E) virtio_pci(E) =
virtio_ring(E) virtio(E) ext4(E) crc16(E) mbcache(E) jbd2(E) loop(E) =
sg(E) dm_multipath(E)
>> [  484.181421]  dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) =
scsi_dh_alua(E) scsi_mod(E) efivarfs(E) autofs4(E)
>> [  484.181583] CPU: 3 PID: 500 Comm: kworker/3:1H Tainted: G          =
  E    4.15.0.ge237f98-master #609
>> [  484.181746] Hardware name: MEDION MS-7848/MS-7848, BIOS =
M7848W08.20C 09/23/2013
>> [  484.181910] Workqueue: kblockd blk_mq_requeue_work
>> [  484.182076] RIP: 0010:__trace_note_message+0x1f/0xd0
>> [  484.182250] RSP: 0018:ffff8803f45bfc20 EFLAGS: 00010282
>> [  484.182436] RAX: 0000000000000000 RBX: ffffffffa0817000 RCX: =
00000000ffff8803
>> [  484.182622] RDX: ffffffff81bf514d RSI: 0000000000000000 RDI: =
ffffffffa0817000
>> [  484.182810] RBP: ffff8803f45bfc80 R08: 0000000000000041 R09: =
ffff8803f69cc5d0
>> [  484.182998] R10: ffff8803f80b47d0 R11: 0000000000001000 R12: =
ffff8803f45e8000
>> [  484.183185] R13: 000000000000000d R14: 0000000000000000 R15: =
ffff8803fba112c0
>> [  484.183372] FS:  0000000000000000(0000) GS:ffff88041ecc0000(0000) =
knlGS:0000000000000000
>> [  484.183561] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [  484.183747] CR2: ffffffffa0817000 CR3: 0000000001e0a006 CR4: =
00000000001606e0
>> [  484.183934] Call Trace:
>> [  484.184122]  bfq_put_queue+0xd3/0xe0
>> [  484.184305]  bfq_finish_requeue_request+0x72/0x350
>> [  484.184493]  __blk_mq_requeue_request+0x8f/0x120
>> [  484.184678]  blk_mq_dispatch_rq_list+0x342/0x550
>> [  484.184866]  ? kyber_dispatch_request+0xd0/0xd0
>> [  484.185053]  blk_mq_sched_dispatch_requests+0xf7/0x180
>> [  484.185238]  __blk_mq_run_hw_queue+0x58/0xd0
>> [  484.185429]  __blk_mq_delay_run_hw_queue+0x99/0xa0
>> [  484.185614]  blk_mq_run_hw_queue+0x54/0xf0
>> [  484.185805]  blk_mq_run_hw_queues+0x4b/0x60
>> [  484.185994]  blk_mq_requeue_work+0x13a/0x150
>> [  484.186192]  process_one_work+0x147/0x350
>> [  484.186383]  worker_thread+0x47/0x3e0
>> [  484.186572]  kthread+0xf8/0x130
>> [  484.186760]  ? rescuer_thread+0x360/0x360
>> [  484.186948]  ? kthread_stop+0x120/0x120
>> [  484.187137]  ret_from_fork+0x35/0x40
>> [  484.187321] Code: ff 48 89 44 24 10 e9 58 fd ff ff 90 55 48 89 e5 =
41 55 41 54 53 48 89 fb 48 83 ec 48 48 89 4c 24 30 4c 89 44 24 38 4c 89 =
4c 24 40 <83> 3f 02 0f 85 87 00 00 00 f6 43 21 04 75 0b 48 83 c4 48 5b =
41=20
>> [  484.187525] RIP: __trace_note_message+0x1f/0xd0 RSP: =
ffff8803f45bfc20
>> [  484.187727] CR2: ffffffffa0817000
>=20
> ok, right in the middle of bfq this time ... Was this the first OOPS =
in your kernel log?
>=20

I've just tried a
list *(__trace_note_message+0x1f)
with gdb, hoping that your image is close enough to mine.  But the
output doesn't say much.

Thanks,
Paolo

> Thanks,
> Paolo
>=20
> --=20
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