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Subject: Re: [PATCHSET v5 0/12] Add support for async buffered reads
To:     sedat.dilek@gmail.com
Cc:     Andres Freund <andres@anarazel.de>, io-uring@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org
References: <20200526195123.29053-1-axboe@kernel.dk>
 <20200604005916.niy2mejjcsx4sv6t@alap3.anarazel.de>
 <e3072371-1d6b-8ae5-d946-d83e60427cb0@kernel.dk>
 <6eeff14f-befc-a5cc-08da-cb77f811fbdf@kernel.dk>
 <20200605202028.d57nklzpeolukni7@alap3.anarazel.de>
 <20200605203613.ogfilu2edcsfpme4@alap3.anarazel.de>
 <75bfe993-008d-71ce-7637-369f130bd984@kernel.dk>
 <3539a454-5321-0bdc-b59c-06f60cc64b56@kernel.dk>
 <34aadc75-5b8a-331e-e149-45e1547b543e@kernel.dk>
 <CA+icZUX=sFOO7q=NYgPaXjQFeJOucFO4H335D+LhG3SgOupGEQ@mail.gmail.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <8637e811-a73f-cb25-c7de-1dd22e86f49f@kernel.dk>
Date:   Sat, 6 Jun 2020 10:04:37 -0600
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On 6/5/20 6:33 PM, Sedat Dilek wrote:
> On Fri, Jun 5, 2020 at 11:24 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> On 6/5/20 3:13 PM, Jens Axboe wrote:
>>> On 6/5/20 2:53 PM, Jens Axboe wrote:
>>>> On 6/5/20 2:36 PM, Andres Freund wrote:
>>>>> Hi,
>>>>>
>>>>> On 2020-06-05 13:20:28 -0700, Andres Freund wrote:
>>>>>> I'll go and try to figure out why I don't see an oops...
>>>>>
>>>>> Err, that probably was a typo on my end in the serial console
>>>>> config. After fixing that, I did get the below.
>>>>>
>>>>> If helpful I can try with debugging enabled or such.
>>>>>
>>>>> [   67.910265] tee (2577): drop_caches: 3
>>>>> [   68.059674] BUG: unable to handle page fault for address: 00007f0b16a3c03c
>>>>> [   68.062021] #PF: supervisor read access in kernel mode
>>>>> [   68.063742] #PF: error_code(0x0000) - not-present page
>>>>> [   68.065517] PGD 102e044067 P4D 102e044067 PUD 102bf7a067 PMD 0
>>>>> [   68.067519] Oops: 0000 [#1] SMP NOPTI
>>>>> [   68.068800] CPU: 2 PID: 2554 Comm: postgres Not tainted 5.7.0-andres-10123-g87823242260e #44
>>>>> [   68.071505] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1 04/01/2014
>>>>> [   68.074139] RIP: 0010:__mutex_lock.isra.0+0x76/0x4e0
>>>>> [   68.075389] Code: b7 01 00 00 48 39 c6 0f 84 a4 03 00 00 65 48 8b 04 25 80 7d 01 00 48 8b 00 a8 08 75 18 49 8b 06 48 83 e0 f8 0f 84 2f 02 00 00 <8b> 50 3c 85 d2 0f 85 12 02 00 00 65 48 8b 04 25 80 7d 01 00 48 8b
>>>>> [   68.079125] RSP: 0018:ffffc90000befd50 EFLAGS: 00010206
>>>>> [   68.080260] RAX: 00007f0b16a3c000 RBX: ffff889037617910 RCX: 0000000000000000
>>>>> [   68.084115] RDX: 00007f0b16a3c000 RSI: ffff88902a4aca80 RDI: ffff8890376178c0
>>>>> [   68.085374] RBP: ffffc90000befdf0 R08: 0000000000000001 R09: 0000000000000000
>>>>> [   68.086409] R10: ffff889037617920 R11: ffff88903f8abaf0 R12: ffffc90000befe08
>>>>> [   68.087447] R13: 0000000000000000 R14: ffff8890376178c0 R15: 0000000000000000
>>>>> [   68.088697] FS:  00007f0b97743740(0000) GS:ffff88903f880000(0000) knlGS:0000000000000000
>>>>> [   68.089903] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [   68.090776] CR2: 00007f0b16a3c03c CR3: 000000102cf7c004 CR4: 0000000000760ee0
>>>>> [   68.091834] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [   68.092902] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [   68.093967] PKRU: 55555554
>>>>> [   68.094427] Call Trace:
>>>>> [   68.094845]  ? __schedule+0x2ac/0x720
>>>>> [   68.095350]  ? schedule+0x55/0xc0
>>>>> [   68.095797]  ? ep_read_events_proc+0xd0/0xd0
>>>>> [   68.096354]  ep_scan_ready_list.constprop.0+0x16c/0x190
>>>>> [   68.097016]  ep_poll+0x2a3/0x440
>>>>> [   68.097449]  ? wait_woken+0x70/0x70
>>>>> [   68.097904]  do_epoll_wait+0xb0/0xd0
>>>>> [   68.098375]  __x64_sys_epoll_wait+0x1a/0x20
>>>>> [   68.098913]  do_syscall_64+0x48/0x130
>>>>> [   68.099393]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>>> [   68.100030] RIP: 0033:0x7f0b97845606
>>>>> [   68.100498] Code: 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 e8 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 90 48 83 ec 28 89 54 24 18 48 89 74 24
>>>>> [   68.102718] RSP: 002b:00007ffe80ffdba8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8
>>>>> [   68.103644] RAX: ffffffffffffffda RBX: 000055fb76a9a998 RCX: 00007f0b97845606
>>>>> [   68.104533] RDX: 0000000000000001 RSI: 000055fb76a9aa10 RDI: 0000000000000005
>>>>> [   68.105418] RBP: 0000000005000007 R08: 0000000005000007 R09: 0000000000000003
>>>>> [   68.106296] R10: 00000000ffffffff R11: 0000000000000246 R12: 000055fb76a9a998
>>>>> [   68.107187] R13: 0000000000000001 R14: 0000000000000009 R15: 000055fb76a9a998
>>>>> [   68.108104] Modules linked in: 9pnet_virtio isst_if_common xhci_pci 9pnet iTCO_wdt intel_pmc_bxt xhci_hcd iTCO_vendor_support
>>>>> [   68.109505] CR2: 00007f0b16a3c03c
>>>>> [   68.109962] ---[ end trace 0ca39a5ed99162ce ]---
>>>>> [   68.110547] RIP: 0010:__mutex_lock.isra.0+0x76/0x4e0
>>>>> [   68.111214] Code: b7 01 00 00 48 39 c6 0f 84 a4 03 00 00 65 48 8b 04 25 80 7d 01 00 48 8b 00 a8 08 75 18 49 8b 06 48 83 e0 f8 0f 84 2f 02 00 00 <8b> 50 3c 85 d2 0f 85 12 02 00 00 65 48 8b 04 25 80 7d 01 00 48 8b
>>>>> [   68.113435] RSP: 0018:ffffc90000befd50 EFLAGS: 00010206
>>>>> [   68.114111] RAX: 00007f0b16a3c000 RBX: ffff889037617910 RCX: 0000000000000000
>>>>> [   68.115016] RDX: 00007f0b16a3c000 RSI: ffff88902a4aca80 RDI: ffff8890376178c0
>>>>> [   68.115902] RBP: ffffc90000befdf0 R08: 0000000000000001 R09: 0000000000000000
>>>>> [   68.116810] R10: ffff889037617920 R11: ffff88903f8abaf0 R12: ffffc90000befe08
>>>>> [   68.117663] R13: 0000000000000000 R14: ffff8890376178c0 R15: 0000000000000000
>>>>> [   68.118520] FS:  00007f0b97743740(0000) GS:ffff88903f880000(0000) knlGS:0000000000000000
>>>>> [   68.119482] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [   68.120181] CR2: 00007f0b16a3c03c CR3: 000000102cf7c004 CR4: 0000000000760ee0
>>>>> [   68.121043] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [   68.121904] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [   68.122790] PKRU: 55555554
>>>>> [   68.123401] general protection fault, probably for non-canonical address 0xfeeda989fef06266: 0000 [#2] SMP NOPTI
>>>>> [   68.125052] CPU: 2 PID: 2554 Comm: postgres Tainted: G      D           5.7.0-andres-10123-g87823242260e #44
>>>>> [   68.126260] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1 04/01/2014
>>>>> [   68.127274] RIP: 0010:__pv_queued_spin_lock_slowpath+0x1a1/0x2b0
>>>>> [   68.128032] Code: c4 c1 ea 12 41 be 01 00 00 00 8d 42 ff 41 83 e4 03 4c 8d 6b 14 49 c1 e4 05 48 98 49 81 c4 00 c7 02 00 4c 03 24 c5 e0 e6 fd 82 <49> 89 1c 24 b8 00 80 00 00 eb 15 84 c0 75 0a 41 0f b6 54 24 14 84
>>>>> [   68.130221] RSP: 0018:ffffc90000befce8 EFLAGS: 00010086
>>>>> [   68.130867] RAX: 0000000000003ffe RBX: ffff88903f8ac700 RCX: 0000000000000001
>>>>> [   68.131752] RDX: 0000000000003fff RSI: 0000000000000000 RDI: 0000000000000000
>>>>> [   68.132637] RBP: ffff889037617924 R08: 0000000000000000 R09: ffffc90000befdf8
>>>>> [   68.133513] R10: ffff8890334d2bf0 R11: 0000000000000018 R12: feeda989fef06266
>>>>> [   68.134399] R13: ffff88903f8ac714 R14: 0000000000000001 R15: 00000000000c0000
>>>>> [   68.135323] FS:  00007f0b97743740(0000) GS:ffff88903f880000(0000) knlGS:0000000000000000
>>>>> [   68.136307] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [   68.137004] CR2: 00007f0b16a3c03c CR3: 000000000360a005 CR4: 0000000000760ee0
>>>>> [   68.137866] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [   68.138748] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [   68.139606] PKRU: 55555554
>>>>> [   68.139973] Call Trace:
>>>>> [   68.140313]  queued_read_lock_slowpath+0x6c/0x70
>>>>> [   68.140915]  _raw_read_lock_irqsave+0x26/0x30
>>>>> [   68.141485]  ep_poll_callback+0x3e/0x2b0
>>>>> [   68.142007]  ? set_next_entity+0xab/0x1f0
>>>>> [   68.142541]  __wake_up_common+0x7a/0x140
>>>>> [   68.143077]  __wake_up_common_lock+0x7c/0xc0
>>>>> [   68.143651]  pipe_release+0x5b/0xd0
>>>>> [   68.144150]  __fput+0xda/0x240
>>>>> [   68.144574]  task_work_run+0x62/0x90
>>>>> [   68.145046]  do_exit+0x35c/0xa70
>>>>> [   68.145505]  ? do_epoll_wait+0xb0/0xd0
>>>>> [   68.146000]  rewind_stack_do_exit+0x17/0x20
>>>>> [   68.146538] RIP: 0033:0x7f0b97845606
>>>>> [   68.146988] Code: Bad RIP value.
>>>>> [   68.147405] RSP: 002b:00007ffe80ffdba8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8
>>>>> [   68.148314] RAX: ffffffffffffffda RBX: 000055fb76a9a998 RCX: 00007f0b97845606
>>>>> [   68.149157] RDX: 0000000000000001 RSI: 000055fb76a9aa10 RDI: 0000000000000005
>>>>> [   68.150021] RBP: 0000000005000007 R08: 0000000005000007 R09: 0000000000000003
>>>>> [   68.150831] R10: 00000000ffffffff R11: 0000000000000246 R12: 000055fb76a9a998
>>>>> [   68.151640] R13: 0000000000000001 R14: 0000000000000009 R15: 000055fb76a9a998
>>>>> [   68.152459] Modules linked in: 9pnet_virtio isst_if_common xhci_pci 9pnet iTCO_wdt intel_pmc_bxt xhci_hcd iTCO_vendor_support
>>>>> [   68.153707] ---[ end trace 0ca39a5ed99162cf ]---
>>>>> [   68.154282] RIP: 0010:__mutex_lock.isra.0+0x76/0x4e0
>>>>> [   68.154884] Code: b7 01 00 00 48 39 c6 0f 84 a4 03 00 00 65 48 8b 04 25 80 7d 01 00 48 8b 00 a8 08 75 18 49 8b 06 48 83 e0 f8 0f 84 2f 02 00 00 <8b> 50 3c 85 d2 0f 85 12 02 00 00 65 48 8b 04 25 80 7d 01 00 48 8b
>>>>> [   68.156976] RSP: 0018:ffffc90000befd50 EFLAGS: 00010206
>>>>> [   68.157614] RAX: 00007f0b16a3c000 RBX: ffff889037617910 RCX: 0000000000000000
>>>>> [   68.158436] RDX: 00007f0b16a3c000 RSI: ffff88902a4aca80 RDI: ffff8890376178c0
>>>>> [   68.159269] RBP: ffffc90000befdf0 R08: 0000000000000001 R09: 0000000000000000
>>>>> [   68.160092] R10: ffff889037617920 R11: ffff88903f8abaf0 R12: ffffc90000befe08
>>>>> [   68.160920] R13: 0000000000000000 R14: ffff8890376178c0 R15: 0000000000000000
>>>>> [   68.161746] FS:  00007f0b97743740(0000) GS:ffff88903f880000(0000) knlGS:0000000000000000
>>>>> [   68.162701] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [   68.163386] CR2: 00007f0b978455dc CR3: 000000000360a005 CR4: 0000000000760ee0
>>>>> [   68.164226] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [   68.165079] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [   68.165931] PKRU: 55555554
>>>>> [   68.166298] Fixing recursive fault but reboot is needed!
>>>>> [  128.173729] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
>>>>> [  128.179267] rcu:         11-...0: (1 GPs behind) idle=c56/1/0x4000000000000000 softirq=6897/6898 fqs=5976
>>>>> [  128.182232] rcu:         19-...0: (1 GPs behind) idle=492/1/0x4000000000000000 softirq=1023/1023 fqs=5976
>>>>> [  128.185217]      (detected by 10, t=18003 jiffies, g=15789, q=631)
>>>>> [  128.186863] Sending NMI from CPU 10 to CPUs 11:
>>>>> [  128.188902] NMI backtrace for cpu 11
>>>>> [  128.188903] CPU: 11 PID: 2546 Comm: postgres Tainted: G      D           5.7.0-andres-10123-g87823242260e #44
>>>>> [  128.188904] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1 04/01/2014
>>>>> [  128.188904] RIP: 0010:queued_read_lock_slowpath+0x5b/0x70
>>>>> [  128.188906] Code: 03 00 02 00 00 8b 03 84 c0 74 08 f3 90 8b 13 84 d2 75 f8 48 89 ef e8 74 e6 ff ff 66 90 5b 5d c3 8b 07 84 c0 74 08 f3 90 8b 03 <84> c0 75 f8 5b 5d c3 89 c6 48 89 ef e8 e4 e8 ff ff 66 90 eb bf 0f
>>>>> [  128.188907] RSP: 0018:ffffc90000348c08 EFLAGS: 00000086
>>>>> [  128.188908] RAX: 0000000037617cc0 RBX: ffff889037617920 RCX: 00000000000000c3
>>>>> [  128.188909] RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff889037617920
>>>>> [  128.188910] RBP: ffff889037bb1a80 R08: 00000000000000c3 R09: ffffc90000348cd8
>>>>> [  128.188910] R10: 0100000000000000 R11: 00000000de2ee17e R12: 0000000000000046
>>>>> [  128.188911] R13: ffff889037617920 R14: 0000000000000001 R15: 00000000000000c3
>>>>> [  128.188912] FS:  00007f0b97743740(0000) GS:ffff88903fac0000(0000) knlGS:0000000000000000
>>>>> [  128.188912] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [  128.188913] CR2: 00007f0b16afc00e CR3: 000000102e5c6002 CR4: 0000000000760ee0
>>>>> [  128.188914] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [  128.188914] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [  128.188915] PKRU: 55555554
>>>>> [  128.188915] Call Trace:
>>>>> [  128.188916]  <IRQ>
>>>>> [  128.188916]  _raw_read_lock_irqsave+0x26/0x30
>>>>> [  128.188917]  ep_poll_callback+0x3e/0x2b0
>>>>> [  128.188917]  ? cpumask_next_and+0x19/0x20
>>>>> [  128.188918]  ? update_sd_lb_stats.constprop.0+0xfe/0x810
>>>>> [  128.188918]  __wake_up_common+0x7a/0x140
>>>>> [  128.188919]  __wake_up_common_lock+0x7c/0xc0
>>>>> [  128.188919]  sock_def_readable+0x37/0x60
>>>>> [  128.188920]  __udp_enqueue_schedule_skb+0x168/0x260
>>>>> [  128.188920]  udpv6_queue_rcv_one_skb+0x284/0x3c0
>>>>> [  128.188921]  udp6_unicast_rcv_skb.isra.0+0x44/0xa0
>>>>> [  128.188921]  ip6_protocol_deliver_rcu+0x235/0x4b0
>>>>> [  128.188922]  ip6_input_finish+0x11/0x20
>>>>> [  128.188922]  ip6_input+0xa2/0xb0
>>>>> [  128.188923]  ? ip6_protocol_deliver_rcu+0x4b0/0x4b0
>>>>> [  128.188923]  ipv6_rcv+0xc0/0xd0
>>>>> [  128.188924]  ? ip6_rcv_finish_core.isra.0+0xd0/0xd0
>>>>> [  128.188924]  __netif_receive_skb_one_core+0x63/0xa0
>>>>> [  128.188925]  process_backlog+0x98/0x140
>>>>> [  128.188925]  net_rx_action+0x13a/0x370
>>>>> [  128.188926]  __do_softirq+0xe0/0x2ca
>>>>> [  128.188926]  do_softirq_own_stack+0x2a/0x40
>>>>> [  128.188926]  </IRQ>
>>>>> [  128.188927]  do_softirq.part.0+0x2b/0x30
>>>>> [  128.188927]  __local_bh_enable_ip+0x4b/0x50
>>>>> [  128.188928]  ip6_finish_output2+0x264/0x5b0
>>>>> [  128.188928]  ip6_output+0x73/0x120
>>>>> [  128.188929]  ? __ip6_finish_output+0x110/0x110
>>>>> [  128.188929]  ip6_send_skb+0x1e/0x60
>>>>> [  128.188930]  udp_v6_send_skb.isra.0+0x197/0x460
>>>>> [  128.188930]  udpv6_sendmsg+0xb4f/0xdb0
>>>>> [  128.188931]  ? ip_reply_glue_bits+0x40/0x40
>>>>> [  128.188931]  ? update_load_avg+0x78/0x630
>>>>> [  128.188932]  ? update_curr+0x73/0x1d0
>>>>> [  128.188932]  ? __sys_sendto+0x108/0x190
>>>>> [  128.188933]  __sys_sendto+0x108/0x190
>>>>> [  128.188933]  ? __fput+0x1a5/0x240
>>>>> [  128.188934]  ? _cond_resched+0x19/0x30
>>>>> [  128.188934]  ? task_work_run+0x67/0x90
>>>>> [  128.188935]  __x64_sys_sendto+0x25/0x30
>>>>> [  128.188935]  do_syscall_64+0x48/0x130
>>>>> [  128.188936]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>>> [  128.188936] RIP: 0033:0x7f0b97a7826c
>>>>> [  128.188945] Code: c0 ff ff ff ff eb b9 0f 1f 80 00 00 00 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 19 45 31 c9 45 31 c0 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 64 c3 0f 1f 00 55 48 83 ec 20 48 89 54 24 10
>>>>> [  128.188946] RSP: 002b:00007ffe80ffcea8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
>>>>> [  128.188947] RAX: ffffffffffffffda RBX: 0000000000000058 RCX: 00007f0b97a7826c
>>>>> [  128.188948] RDX: 0000000000000058 RSI: 000055fb765264c0 RDI: 0000000000000009
>>>>> [  128.188949] RBP: 000055fb765264c0 R08: 0000000000000000 R09: 0000000000000000
>>>>> [  128.188949] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe80ffcfc0
>>>>> [  128.188950] R13: 000000000002c600 R14: 0000000000000000 R15: 000055fb7629b751
>>>>> [  128.188957] Sending NMI from CPU 10 to CPUs 19:
>>>>> [  128.239939] NMI backtrace for cpu 19
>>>>> [  128.239940] CPU: 19 PID: 2587 Comm: postgres Tainted: G      D           5.7.0-andres-10123-g87823242260e #44
>>>>> [  128.239940] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1 04/01/2014
>>>>> [  128.239940] RIP: 0010:kvm_wait+0x30/0x50
>>>>> [  128.239941] Code: 8b 05 ac cb f4 7e a9 00 00 f0 00 75 1f 9c 58 fa 0f b6 17 40 38 d6 75 12 f6 c4 02 75 10 e9 07 00 00 00 0f 00 2d 6f ce 54 01 f4 <50> 9d c3 e9 07 00 00 00 0f 00 2d 5f ce 54 01 fb f4 eb ed 66 66 2e
>>>>> [  128.239942] RSP: 0018:ffffc90000cc78e8 EFLAGS: 00000046
>>>>> [  128.239942] RAX: 0000000000000046 RBX: ffff88903fcec700 RCX: 0000000000000008
>>>>> [  128.239943] RDX: 0000000000000003 RSI: 0000000000000003 RDI: ffff889039049d80
>>>>> [  128.239943] RBP: ffff889039049d80 R08: ffff88907ffe9f80 R09: 00000000000000f8
>>>>> [  128.239944] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
>>>>> [  128.239944] R13: 0000000000000001 R14: 0000000000000100 R15: 0000000000500000
>>>>> [  128.239944] FS:  00007f0b97743740(0000) GS:ffff88903fcc0000(0000) knlGS:0000000000000000
>>>>> [  128.239945] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> [  128.239945] CR2: 000055fb76a96030 CR3: 0000001035882004 CR4: 0000000000760ee0
>>>>> [  128.239945] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>>> [  128.239946] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>>> [  128.239946] PKRU: 55555554
>>>>> [  128.239946] Call Trace:
>>>>> [  128.239946]  __pv_queued_spin_lock_slowpath+0x26e/0x2b0
>>>>> [  128.239947]  _raw_spin_lock_irqsave+0x25/0x30
>>>>> [  128.239947]  __wake_up_common_lock+0x62/0xc0
>>>>> [  128.239947]  sock_def_write_space+0x49/0x90
>>>>> [  128.239948]  sock_wfree+0x68/0xb0
>>>>> [  128.239948]  loopback_xmit+0x49/0xe0
>>>>> [  128.239948]  dev_hard_start_xmit+0x8d/0x1e0
>>>>> [  128.239948]  __dev_queue_xmit+0x721/0x8e0
>>>>> [  128.239949]  ip6_finish_output2+0x250/0x5b0
>>>>> [  128.239949]  ip6_output+0x73/0x120
>>>>> [  128.239949]  ? __ip6_finish_output+0x110/0x110
>>>>> [  128.239950]  ip6_send_skb+0x1e/0x60
>>>>> [  128.239950]  udp_v6_send_skb.isra.0+0x197/0x460
>>>>> [  128.239950]  udpv6_sendmsg+0xb4f/0xdb0
>>>>> [  128.239950]  ? release_pages+0x28f/0x2f0
>>>>> [  128.239950]  ? ip_reply_glue_bits+0x40/0x40
>>>>> [  128.239951]  ? _cond_resched+0x19/0x30
>>>>> [  128.239951]  ? unmap_page_range+0x678/0xa60
>>>>> [  128.239951]  ? __sys_sendto+0x108/0x190
>>>>> [  128.239951]  __sys_sendto+0x108/0x190
>>>>> [  128.239952]  ? __fput+0x1a5/0x240
>>>>> [  128.239952]  ? _cond_resched+0x19/0x30
>>>>> [  128.239952]  ? task_work_run+0x67/0x90
>>>>> [  128.239952]  __x64_sys_sendto+0x25/0x30
>>>>> [  128.239953]  do_syscall_64+0x48/0x130
>>>>> [  128.239953]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>>> [  128.239953] RIP: 0033:0x7f0b97a7826c
>>>>> [  128.239954] Code: c0 ff ff ff ff eb b9 0f 1f 80 00 00 00 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 19 45 31 c9 45 31 c0 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 64 c3 0f 1f 00 55 48 83 ec 20 48 89 54 24 10
>>>>> [  128.239954] RSP: 002b:00007ffe80ffd7b8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
>>>>> [  128.239955] RAX: ffffffffffffffda RBX: 00000000000003a8 RCX: 00007f0b97a7826c
>>>>> [  128.239955] RDX: 00000000000003a8 RSI: 00007ffe80ffd800 RDI: 0000000000000009
>>>>> [  128.239955] RBP: 00007ffe80ffd800 R08: 0000000000000000 R09: 0000000000000000
>>>>> [  128.239956] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe80ffd800
>>>>> [  128.239956] R13: 00007ffe80ffd800 R14: 000000000000000e R15: 000055fb76b37e58
>>>>
>>>> I can reproduce this, and I see what it is. I'll send out a patch soonish.
>>>
>>> Thinko, can you try with this on top?
>>
>> Sorry that was incomplete, please use this one!
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index d22830a423f1..0075107dd09a 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -2779,7 +2779,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
>>                         ret = io_setup_async_rw(req, io_size, iovec,
>>                                                 inline_vecs, &iter);
>>                         if (ret)
>> -                               goto out_free;
>> +                               goto out;
>>                         /* any defer here is final, must blocking retry */
>>                         if (!(req->flags & REQ_F_NOWAIT) &&
>>                             !file_can_poll(req->file))
>> @@ -2787,18 +2787,18 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
>>                         /* if we can retry, do so with the callbacks armed */
>>                         if (io_rw_should_retry(req)) {
>>                                 ret2 = io_iter_do_read(req, &iter);
>> -                               if (ret2 != -EAGAIN) {
>> +                               if (ret2 == -EIOCBQUEUED) {
>> +                                       goto out;
>> +                               } else if (ret2 != -EAGAIN) {
>>                                         kiocb_done(kiocb, ret2);
>> -                                       goto out_free;
>> +                                       goto out;
>>                                 }
>>                         }
>>                         kiocb->ki_flags &= ~IOCB_WAITQ;
>>                         return -EAGAIN;
>>                 }
>>         }
>> -out_free:
>> -       kfree(iovec);
>> -       req->flags &= ~REQ_F_NEED_CLEANUP;
>> +out:
>>         return ret;
>>  }
>>
>> --
>> Jens Axboe
>>
> 
> Hi Jens,
> 
> I have tested with today's linux-block.git#async-buffered.7 and my
> usual testcases:
> 
> [ FIO ]
> 
> root# echo 1 > /sys/kernel/debug/tracing/events/io_uring/io_uring_create/enable
> 
> root# cat /sys/kernel/debug/tracing/events/io_uring/io_uring_create/enable
> 1
> 
> root# cat buf-test-dileks-min
> [buf-test-dileks-min]
> filename=/mnt/backup/thinkpad-t530/home/sdi/Downloads/iso-images/iso_debian-stretch/firmware-stretch-live-amd64/debian-live-9.2.0-amd64-kde+nonfree.iso
> buffered=1
> ioengine=io_uring
> 
> root# fio ./buf-test-dileks-min
> buf-test-dileks-min: (g=0): rw=read, bs=(R) 4096B-4096B, (W)
> 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=1
> fio-3.20
> Starting 1 process
> Jobs: 1 (f=1): [R(1)][100.0%][r=87.1MiB/s][r=22.3k IOPS][eta 00m:00s]
> buf-test-dileks-min: (groupid=0, jobs=1): err= 0: pid=4076: Sat Jun  6
> 02:22:20 2020
>   read: IOPS=20.8k, BW=81.2MiB/s (85.1MB/s)(2811MiB/34626msec)
>     slat (usec): min=2, max=395, avg= 8.95, stdev=18.43
>     clat (nsec): min=130, max=159571k, avg=36797.18, stdev=520010.15
>      lat (usec): min=2, max=159779, avg=46.04, stdev=528.95
>     clat percentiles (nsec):
>      |  1.00th=[     225],  5.00th=[     302], 10.00th=[     330],
>      | 20.00th=[     358], 30.00th=[     378], 40.00th=[     390],
>      | 50.00th=[     406], 60.00th=[     418], 70.00th=[     430],
>      | 80.00th=[     446], 90.00th=[     478], 95.00th=[     732],
>      | 99.00th=[ 1531904], 99.50th=[ 1695744], 99.90th=[ 3555328],
>      | 99.95th=[ 3686400], 99.99th=[16711680]
>    bw (  KiB/s): min=34235, max=94554, per=100.00%, avg=83141.75,
> stdev=11118.80, samples=69
>    iops        : min= 8558, max=23638, avg=20785.14, stdev=2779.73, samples=69
>   lat (nsec)   : 250=1.63%, 500=89.57%, 750=3.94%, 1000=0.85%
>   lat (usec)   : 2=1.55%, 4=0.21%, 10=0.03%, 20=0.01%, 50=0.02%
>   lat (usec)   : 100=0.01%, 250=0.50%, 500=0.11%, 750=0.02%, 1000=0.01%
>   lat (msec)   : 2=1.18%, 4=0.34%, 10=0.01%, 20=0.01%, 50=0.01%
>   lat (msec)   : 100=0.01%, 250=0.01%
>   cpu          : usr=9.80%, sys=17.79%, ctx=15869, majf=0, minf=15
>   IO depths    : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
>      submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
>      complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
>      issued rwts: total=719568,0,0,0 short=0,0,0,0 dropped=0,0,0,0
>      latency   : target=0, window=0, percentile=100.00%, depth=1
> 
> Run status group 0 (all jobs):
>    READ: bw=81.2MiB/s (85.1MB/s), 81.2MiB/s-81.2MiB/s
> (85.1MB/s-85.1MB/s), io=2811MiB (2947MB), run=34626-34626msec
> 
> Disk stats (read/write):
>   sdc: ios=15784/53, merge=0/89, ticks=57005/536, in_queue=58011, util=99.75%
> 
> root# fio --showcmd ./buf-test-dileks-min
> fio --name=buf-test-dileks-min --buffered=1 --ioengine=io_uring
> --filename=/mnt/backup/thinkpad-t530/home/sdi/Downloads/iso-images/iso_debian-stretch/firmware-stretch-live-amd64/debian-live-9.2.0-amd64-kde+nonfree.iso
> 
> root# tail /sys/kernel/debug/tracing/trace
> # entries-in-buffer/entries-written: 1/1   #P:4
> #
> #                              _-----=> irqs-off
> #                             / _----=> need-resched
> #                            | / _---=> hardirq/softirq
> #                            || / _--=> preempt-depth
> #                            ||| /     delay
> #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
> #              | |       |   ||||       |         |
>              fio-4076  [001] ....   641.669846: io_uring_create: ring
> 00000000a88caba9, fd 5 sq size 1, cq size 2, flags 0
> 
> 
> [ SYSTEMD-ANALYZE ]
> 
> user$ sudo systemd-analyze --no-pager time
> Startup finished in 6.228s (kernel) + 41.559s (userspace) = 47.787s
> graphical.target reached after 41.539s in userspace
> 
> user$ sudo systemd-analyze --no-pager blame
> 19.800s accounts-daemon.service
> 19.001s udisks2.service
> 13.282s NetworkManager-wait-online.service
>  9.956s polkit.service
>  9.590s avahi-daemon.service
>  9.479s NetworkManager.service
>  9.436s rtkit-daemon.service
>  9.367s systemd-logind.service
>  9.272s switcheroo-control.service
>  9.257s wpa_supplicant.service
>  9.215s dev-sdc2.device
>  9.079s powertop.service
>  8.875s smartmontools.service
>  8.108s ModemManager.service
>  7.070s zramswap.service
>  5.443s networking.service
>  5.181s rsyslog.service
>  4.870s gpm.service
>  3.846s e2scrub_reap.service
>  3.718s systemd-fsck@dev-disk-by\x2duuid-cfd78a9b\x2dfadd\x2d4870\x2d88c2\x2d5277dae4e59f.service
>  3.550s apparmor.service
>  1.807s systemd-journal-flush.service
>  1.570s systemd-tmpfiles-setup.service
>  1.269s keyboard-setup.service
>  1.259s atd.service
>  1.207s systemd-udevd.service
>  1.055s bluetooth.service
>  1.052s binfmt-support.service
>   935ms exim4.service
>   901ms systemd-journald.service
>   850ms systemd-modules-load.service
>   843ms systemd-sysusers.service
>   814ms upower.service
>   807ms dev-hugepages.mount
>   803ms pppd-dns.service
>   790ms dev-mqueue.mount
>   771ms sys-kernel-debug.mount
>   770ms sys-kernel-tracing.mount
>   697ms systemd-timesyncd.service
>   677ms modprobe@drm.service
>   630ms ifupdown-wait-online.service
>   604ms systemd-rfkill.service
>   561ms systemd-tmpfiles-setup-dev.service
>   521ms systemd-remount-fs.service
>   476ms systemd-sysctl.service
>   397ms systemd-random-seed.service
>   394ms systemd-backlight@backlight:intel_backlight.service
>   376ms systemd-tmpfiles-clean.service
>   289ms kmod-static-nodes.service
>   269ms user@1000.service
>   194ms console-setup.service
>   182ms systemd-udev-trigger.service
>   134ms systemd-update-utmp.service
>   125ms proc-sys-fs-binfmt_misc.mount
>    69ms systemd-user-sessions.service
>    52ms alsa-restore.service
>    21ms user-runtime-dir@1000.service
>    17ms mnt-sandisk.mount
>    13ms systemd-update-utmp-runlevel.service
>     6ms sys-fs-fuse-connections.mount
>     4ms ifupdown-pre.service
> 
> user$ sudo systemd-analyze --no-pager critical-chain
> The time when unit became active or started is printed after the "@" character.
> The time the unit took to start is printed after the "+" character.
> 
> graphical.target @41.539s
> └─multi-user.target @41.538s
>   └─exim4.service @40.601s +935ms
>     └─network-online.target @40.599s
>       └─NetworkManager-wait-online.service @27.314s +13.282s
>         └─NetworkManager.service @17.831s +9.479s
>           └─dbus.service @17.824s
>             └─basic.target @17.675s
>               └─sockets.target @17.672s
>                 └─dbus.socket @17.670s
>                   └─sysinit.target @17.584s
>                     └─systemd-udev-trigger.service @26.747s +182ms
>                       └─systemd-udevd-kernel.socket @3.027s
>                         └─system.slice @2.440s
>                           └─-.slice @2.440s
> 
> Hope this helps you.
> 
> If you want some further informations and/or testing, please let me
> know and give clear instructions.

Thanks for testing, appreciate it!

-- 
Jens Axboe