Return-Path: Received: from mail-pa0-f46.google.com ([209.85.220.46]:35586 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752976AbbK3C5V (ORCPT ); Sun, 29 Nov 2015 21:57:21 -0500 Received: by pacej9 with SMTP id ej9so168946626pac.2 for ; Sun, 29 Nov 2015 18:57:21 -0800 (PST) Subject: Re: [PATCH RFC] nfsd: serialize layout stateid morphing operations To: Jeff Layton References: <1442491104-30080-1-git-send-email-jeff.layton@primarydata.com> <565A7A14.4010902@gmail.com> <20151129084614.42fb1272@tlielax.poochiereds.net> Cc: bfields@fieldses.org, Christoph Hellwig , linux-nfs@vger.kernel.org, kinglongmee@gmail.com From: Kinglong Mee Message-ID: <565BBB03.7020206@gmail.com> Date: Mon, 30 Nov 2015 10:57:07 +0800 MIME-Version: 1.0 In-Reply-To: <20151129084614.42fb1272@tlielax.poochiereds.net> Content-Type: text/plain; charset=windows-1252 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 11/29/2015 21:46, Jeff Layton wrote: > On Sun, 29 Nov 2015 12:07:48 +0800 > Kinglong Mee wrote: > >> I meet two problems with this patch, >> > > Ok, I was less sure of this patch than the other one. I think we will > need to serialize these operations, but this may not be the best way to > do it. > > Bruce if you want to back this one for now, then I'm fine with that. It > may be a bit before I can get to it. > > >> 1. a dump_stack messages printed in process_one_work() at kernel/workqueue.c. >> >> BUG: workqueue leaked lock or atomic: kworker/u2:4/0x00000000/98#012 last function: nfsd4_run_cb_work [nfsd] >> 1 lock held by kworker/u2:4/98: >> #0: (&ls->ls_mutex){......}, at: [] nfsd4_cb_layout_prepare+0x24/0x40 [nfsd] >> CPU: 0 PID: 98 Comm: kworker/u2:4 Not tainted 4.4.0-rc2+ #333 >> Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 >> Workqueue: nfsd4_callbacks nfsd4_run_cb_work [nfsd] >> ffff8800362b9e40 000000007fe9394f ffff880036353d58 ffffffff8136dc64 >> ffff880036353dd8 ffffffff810a3f12 ffffffff810a3cbd 000000000000000a >> ffffffffa0261d78 ffffffff82902e20 0000000000000000 ffffffffa0259241 >> Call Trace: >> [] dump_stack+0x19/0x25 >> [] process_one_work+0x3c2/0x4c0 >> [] ? process_one_work+0x16d/0x4c0 >> [] worker_thread+0x4a/0x440 >> [] ? process_one_work+0x4c0/0x4c0 >> [] ? process_one_work+0x4c0/0x4c0 >> [] kthread+0xf5/0x110 >> [] ? kthread_create_on_node+0x240/0x240 >> [] ret_from_fork+0x3f/0x70 >> [] ? kthread_create_on_node+0x240/0x240 >> > > > I guess this is just a general "hey you left a mutex locked" warning > when finishing a workqueue job? This patch actually does want to do > that, but I trying to tell that to lockdep may be tricky... Yes, it's just a warning. But, it's terrible that kernel prints it every time when calling nfsd4_cb_layout_prepare. > > >> 2. a mutex race between layoutrecall and layoutcommit, >> >> callback thread, >> nfsd4_cb_layout_prepare >> --->mutex_lock(&ls->ls_mutex); >> >> layoutcommit thread, >> nfsd4_layoutcommit >> ---> nfsd4_preprocess_layout_stateid >> --> mutex_lock(&ls->ls_mutex); <---------------- hang >> >> [ 600.645142] INFO: task nfsd:11623 blocked for more than 120 seconds. >> [ 600.646337] Not tainted 4.4.0-rc2+ #332 >> [ 600.647404] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> [ 600.648546] nfsd D ffff880064277b80 0 11623 2 0x00000000 >> [ 600.649803] ffff880064277b80 ffff880064278000 00000000ffffffff ffff88005dd241a8 >> [ 600.651021] ffffffffa025e77c 0000000000000246 ffff880064277b98 ffffffff81733103 >> [ 600.652255] ffff880063d7e100 ffff880064277ba8 ffffffff8173330e ffff880064277c28 >> [ 600.653512] Call Trace: >> [ 600.654765] [] ? nfsd4_preprocess_layout_stateid+0x37c/0x400 [nfsd] >> [ 600.656084] [] schedule+0x33/0x80 >> [ 600.657405] [] schedule_preempt_disabled+0xe/0x10 >> [ 600.658741] [] mutex_lock_nested+0x145/0x330 >> [ 600.660094] [] ? nfsd4_preprocess_layout_stateid+0x37c/0x400 [nfsd] >> [ 600.661696] [] nfsd4_preprocess_layout_stateid+0x37c/0x400 [nfsd] >> [ 600.663129] [] ? nfsd4_preprocess_layout_stateid+0x5/0x400 [nfsd] >> [ 600.664558] [] ? printk+0x56/0x72 >> [ 600.665990] [] nfsd4_layoutcommit+0x13c/0x200 [nfsd] >> [ 600.667365] [] nfsd4_proc_compound+0x388/0x660 [nfsd] >> [ 600.668835] [] nfsd_dispatch+0xb8/0x200 [nfsd] >> [ 600.670323] [] svc_process_common+0x409/0x650 [sunrpc] >> [ 600.671836] [] svc_process+0xf4/0x190 [sunrpc] >> [ 600.673328] [] nfsd+0x135/0x1a0 [nfsd] >> [ 600.674825] [] ? nfsd+0x5/0x1a0 [nfsd] >> [ 600.676388] [] ? nfsd_destroy+0xb0/0xb0 [nfsd] >> [ 600.677884] [] kthread+0xf5/0x110 >> [ 600.679373] [] ? kthread_create_on_node+0x240/0x240 >> [ 600.680874] [] ret_from_fork+0x3f/0x70 >> [ 600.682398] [] ? kthread_create_on_node+0x240/0x240 >> [ 600.683893] 1 lock held by nfsd/11623: >> [ 600.685449] #0: (&ls->ls_mutex){......}, at: [] nfsd4_preprocess_layout_stateid+0x37c/0x400 [nfsd] >> [ 600.688778] Sending NMI to all CPUs: >> [ 600.690854] NMI backtrace for cpu 0 >> [ 600.691909] CPU: 0 PID: 11 Comm: khungtaskd Not tainted 4.4.0-rc2+ #332 >> [ 600.692523] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 >> [ 600.693821] task: ffff88007b900000 ti: ffff88007b8fc000 task.ti: ffff88007b8fc000 >> [ 600.694496] RIP: 0010:[] [] native_write_msr_safe+0xa/0x10 >> [ 600.695185] RSP: 0018:ffff88007b8ffd70 EFLAGS: 00000046 >> [ 600.695861] RAX: 0000000000000400 RBX: 0000000000000286 RCX: 0000000000000830 >> [ 600.696539] RDX: 0000000000000000 RSI: 0000000000000400 RDI: 0000000000000830 >> [ 600.697204] RBP: ffff88007b8ffd70 R08: 0000000000000400 R09: 0000000000000000 >> [ 600.697862] R10: 00000000000000e4 R11: 0000000000000001 R12: ffff880063d7e100 >> [ 600.698513] R13: 00000000003fff3c R14: ffff880063d7e308 R15: 0000000000000004 >> [ 600.699156] FS: 0000000000000000(0000) GS:ffffffff81c27000(0000) knlGS:0000000000000000 >> [ 600.699823] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 600.700459] CR2: 00007f366afd4000 CR3: 000000005dd56000 CR4: 00000000001406f0 >> [ 600.701106] Stack: >> [ 600.701745] ffff88007b8ffd88 ffffffff8104a860 ffffffff81047340 ffff88007b8ffd98 >> [ 600.702404] ffffffff8104a885 ffff88007b8ffda8 ffffffff8104735b ffff88007b8ffdd8 >> [ 600.703058] ffffffff813723ad 0000000000000078 ffff880063d7e100 00000000003fff3c >> [ 600.703712] Call Trace: >> [ 600.704355] [] __x2apic_send_IPI_mask.isra.2+0x60/0x70 >> [ 600.705017] [] ? setup_vector_irq+0x130/0x130 >> [ 600.705676] [] x2apic_send_IPI_mask+0x15/0x20 >> [ 600.706335] [] nmi_raise_cpu_backtrace+0x1b/0x20 >> [ 600.706989] [] nmi_trigger_all_cpu_backtrace+0x14d/0x1c0 >> [ 600.707693] [] arch_trigger_all_cpu_backtrace+0x19/0x20 >> [ 600.708362] [] watchdog+0x32f/0x370 >> [ 600.709031] [] ? watchdog+0x81/0x370 >> [ 600.709725] [] ? reset_hung_task_detector+0x20/0x20 >> [ 600.710398] [] kthread+0xf5/0x110 >> [ 600.711067] [] ? kthread_create_on_node+0x240/0x240 >> [ 600.711739] [] ret_from_fork+0x3f/0x70 >> [ 600.712405] [] ? kthread_create_on_node+0x240/0x240 >> [ 600.713073] Code: 00 55 89 f9 48 89 e5 0f 32 45 31 c0 48 c1 e2 20 44 89 06 48 09 d0 5d c3 66 0f 1f 84 00 00 00 00 00 55 89 f0 89 f9 48 89 e5 0f 30 <31> c0 5d c3 66 90 55 89 f9 48 89 e5 0f 33 48 c1 e2 20 48 09 d0 >> [ 600.715196] Kernel panic - not syncing: hung_task: blocked tasks >> [ 600.715889] CPU: 0 PID: 11 Comm: khungtaskd Not tainted 4.4.0-rc2+ #332 >> [ 600.716540] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 >> [ 600.717910] ffffffff81a4d19c 00000000480750be ffff88007b8ffd60 ffffffff8136dbf4 >> [ 600.718610] ffff88007b8ffde8 ffffffff81173559 ffff880000000008 ffff88007b8ffdf8 >> [ 600.719302] ffff88007b8ffd90 00000000480750be 0000000000000001 0000000000000001 >> [ 600.719984] Call Trace: >> [ 600.720646] [] dump_stack+0x19/0x25 >> [ 600.721330] [] panic+0xd3/0x212 >> [ 600.722009] [] watchdog+0x33b/0x370 >> [ 600.722686] [] ? watchdog+0x81/0x370 >> [ 600.723213] [] ? reset_hung_task_detector+0x20/0x20 >> [ 600.723674] [] kthread+0xf5/0x110 >> [ 600.724107] [] ? kthread_create_on_node+0x240/0x240 >> [ 600.724509] [] ret_from_fork+0x3f/0x70 >> [ 600.724903] [] ? kthread_create_on_node+0x240/0x240 >> >> thanks, >> Kinglong Mee >> > > This is the bigger problem, I think. The question of course is why the > client didn't respond to the cb request? Still, holding a mutex across > the callback RPC is pretty ugly and now that I think about it, I don't > think it's really necessary anyway. Once we've copied the stateid, we > aren't really changing anything else so we can let other layout ops > proceed. > > Would a patch like this fix it? Yes, it's great. With this patch, every thing is okay. > > -----------------------8<-------------------------- > > [PATCH] nfsd: don't hold ls_mutex across a layout recall > > We do need to serialize layout stateid morphing operations, but we > currently hold the ls_mutex across a layout recall which is pretty > ugly. It's also unnecessary -- once we've bumped the seqid and > copied it, we don't need to serialize the rest of the CB_LAYOUTRECALL > vs. anything else. Just drop the mutex once the copy is done. > > Fixes: cc8a55320b5f "nfsd: serialize layout stateid morphing operations" > Cc: stable@vger.kernel.org > Reported-by: Kinglong Mee > Signed-off-by: Jeff Layton Tested-by: Kinglong Mee thanks, Kinglong Mee > --- > fs/nfsd/nfs4layouts.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c > index 9ffef06b30d5..c9d6c715c0fb 100644 > --- a/fs/nfsd/nfs4layouts.c > +++ b/fs/nfsd/nfs4layouts.c > @@ -616,6 +616,7 @@ nfsd4_cb_layout_prepare(struct nfsd4_callback *cb) > > mutex_lock(&ls->ls_mutex); > nfs4_inc_and_copy_stateid(&ls->ls_recall_sid, &ls->ls_stid); > + mutex_unlock(&ls->ls_mutex); > } > > static int > @@ -659,7 +660,6 @@ nfsd4_cb_layout_release(struct nfsd4_callback *cb) > > trace_layout_recall_release(&ls->ls_stid.sc_stateid); > > - mutex_unlock(&ls->ls_mutex); > nfsd4_return_all_layouts(ls, &reaplist); > nfsd4_free_layouts(&reaplist); > nfs4_put_stid(&ls->ls_stid); >