On Thu, Apr 8, 2021 at 2:50 PM Dennis Zhou <den...@kernel.org> wrote:
>
> On Thu, Apr 08, 2021 at 05:20:00PM +0800, Wang Yugui wrote:
> > Hi,
> >
> > > On Thu, Apr 08, 2021 at 07:28:01AM +0800, Wang Yugui wrote:
> > > > Hi,
> > > >
> > > > > > > > upper caller:
> > > > > > > > nofs_flag = memalloc_nofs_save();
> > > > > > > > ret = btrfs_drew_lock_init(&root->snapshot_lock);
> > > > > > > > memalloc_nofs_restore(nofs_flag);
> > > > >
> > > > > The issue is here. nofs is set which means percpu attempts an atomic
> > > > > allocation. If it cannot find anything already allocated it isn't
> > > > > happy.
> > > > > This was done before memalloc_nofs_{save/restore}() were pervasive.
> > > > >
> > > > > Percpu should probably try to allocate some pages if possible even if
> > > > > nofs is set.
> > > >
> > > > Thanks.
> > > >
> > > > I will wait for the patch, and then test it.
> > > >
> > >
> > > I'm currently a bit busy with some other things. Adding support I don't
> > > think will be much work, just a little bit tricky.
> > >
> > > I recommend carrying what you have minus the change to reserved percpu
> > > memory for now. If I'm the one to write it, I'll cc you.
> > >
> > > Thanks,
> > > Dennis
> >
> >
> > In the recent test, another problem is triggered too with my extended
> > percpu buffer size patch. maybe this info is helpful.
> >
> > problem:
> > OS/VGA console is freezed , and no call stace is outputed.
> > Just some info is outputed to IPMI/dell iDRAC
> > 2 | 04/03/2021 | 11:35:01 | OS Critical Stop #0x46 | Run-time critical
> > stop () | Asserted
> > 3 | Linux kernel panic: Fatal excep
> > 4 | Linux kernel panic: tion
> > 5 | 04/05/2021 | 19:09:14 | OS Critical Stop #0x46 | Run-time critical
> > stop () | Asserted
> > 6 | Linux kernel panic: Fatal excep
> > 7 | Linux kernel panic: tion
> > 8 | 04/06/2021 | 13:08:42 | OS Critical Stop #0x46 | Run-time critical
> > stop () | Asserted
> > 9 | Linux kernel panic: Fatal excep
> > a | Linux kernel panic: tion
> > b | 04/08/2021 | 02:12:46 | OS Critical Stop #0x46 | Run-time critical
> > stop () | Asserted
> > c | Linux kernel panic: Fatal excep
> > d | Linux kernel panic: tion
>
> Unfortunately non of the above to me is useful.
>
> > kernel: at least 5.10.26/5.10.27/5.10.28
> >
> > This problem is triggered by our application, NOT xfstests.
> > But our applicaiton have some heavy write load just like
> > xfstest/generic/476.
> > Our application use at most 75% of memory, if still not enough,
> > it will write out all buffer info to filesystem.
>
> Do you use cgroups at all? If yes can you describe the workload pattern
> a bit.
>
> > This problem is happen in linux kernel 5.10.x, but not happen in linux
> > kernel 5.4.x. It have high frequency to repduce too.
>
> Ah. Can you try the following patch?
> https://lore.kernel.org/lkml/20210408035736.883861-4-g...@fb.com/
Btw, this has been happening since 5.9.
I never managed to find the time to bisect it, but it might be more
obvious to you or anyone else with deep experience of mm/percpu of
what changed.
It's triggered very frequently with long runs of fsstress on btrfs,
such as with test cases btrfs/078 and generic/476 from fstests.
It produces a trace like the following:
[128063.794597] ------------[ cut here ]------------
[128063.795305] BTRFS: Transaction aborted (error -12)
[128063.795831] WARNING: CPU: 0 PID: 1131545 at
fs/btrfs/transaction.c:1683 create_pending_snapshot+0xa2a/0xfd0
[btrfs]
[128063.796235] Modules linked in: dm_snapshot btrfs dm_thin_pool
dm_persistent_data dm_bio_prison dm_bufio dm_log_writes dm_dust
dm_flakey dm_mod loop xfs blake2b_generic xor raid6_pq libcrc32c
intel_rapl_msr intel_rapl_common kvm_intel kvm irqbypass
crct10dif_pclmul g>
[128063.798521] CPU: 0 PID: 1131545 Comm: fsstress Tainted: G W
5.10.0-rc2-btrfs-next-71 #1
[128063.799102] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[128063.800150] RIP: 0010:create_pending_snapshot+0xa2a/0xfd0 [btrfs]
[128063.800748] Code: 02 72 30 83 f8 fb 0f 84 38 03 00 00 83 f8 e2 0f
84 2f 03 00 00 89 c6 48 c7 c7 e8 af c5 c0 48 89 85 78 ff ff ff e8 6d
29 6b ca <0f> 0b 48 8b 85 78 ff ff ff 89 c1 ba 93 06 00 00 48 c7 c6 90
a6 c4
[128063.801886] RSP: 0018:ffffaad1444cfd50 EFLAGS: 00010282
[128063.802529] RAX: 0000000000000000 RBX: ffff99c4c0d0b500 RCX:
0000000000000000
[128063.803175] RDX: 0000000000000001 RSI: 0000000000000027 RDI:
00000000ffffffff
[128063.803829] RBP: ffffaad1444cfe20 R08: 0000000000000000 R09:
0000000000000000
[128063.804478] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff99c70a1a4c10
[128063.805134] R13: ffff99c59e3d0e00 R14: ffff99c70e935d08 R15:
00000000fffffff4
[128063.805816] FS: 00007f0fdd733240(0000) GS:ffff99c7ebe00000(0000)
knlGS:0000000000000000
[128063.806547] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[128063.807264] CR2: 00007f0fdd731000 CR3: 00000001ee3b6003 CR4:
00000000003706f0
[128063.807998] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[128063.808707] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[128063.809415] Call Trace:
[128063.810172] ? create_pending_snapshots+0xaa/0xd0 [btrfs]
[128063.810921] create_pending_snapshots+0xaa/0xd0 [btrfs]
[128063.811680] btrfs_commit_transaction+0x2b6/0xb80 [btrfs]
[128063.812429] ? finish_wait+0x90/0x90
[128063.813176] ? __ia32_sys_fdatasync+0x20/0x20
[128063.813898] iterate_supers+0x87/0xf0
[128063.814562] ksys_sync+0x60/0xb0
[128063.815214] __do_sys_sync+0xa/0x10
[128063.815879] do_syscall_64+0x33/0x80
[128063.816539] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[128063.817191] RIP: 0033:0x7f0fdd829bd7
[128063.817907] Code: ff ff ff ff c3 66 0f 1f 44 00 00 48 8b 15 b1 82
0c 00 f7 d8 64 89 02 b8 ff ff ff ff eb b8 0f 1f 44 00 00 b8 a2 00 00
00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 89 82 0c 00 f7 d8 64 89
01 48
[128063.819411] RSP: 002b:00007fff356b8968 EFLAGS: 00000206 ORIG_RAX:
00000000000000a2
[128063.820233] RAX: ffffffffffffffda RBX: 000055acc4127560 RCX:
00007f0fdd829bd7
[128063.821028] RDX: 00000000ffffffff RSI: 000000002ecb3555 RDI:
00000000000069f4
[128063.821808] RBP: 000000000000c350 R08: 0000000000000014 R09:
00007fff356b893c
[128063.822632] R10: 00007fff356b8565 R11: 0000000000000206 R12:
00000000000069f4
[128063.823416] R13: 00007fff356b89d0 R14: 00007fff356b8986 R15:
000055acc4115350
[128063.824249] CPU: 5 PID: 1131545 Comm: fsstress Tainted: G W
5.10.0-rc2-btrfs-next-71 #1
[128063.824931] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[128063.826439] Call Trace:
[128063.827119] dump_stack+0x8d/0xb5
[128063.827804] ? create_pending_snapshot+0xa2a/0xfd0 [btrfs]
[128063.828456] __warn.cold+0x24/0x4b
[128063.829100] ? create_pending_snapshot+0xa2a/0xfd0 [btrfs]
[128063.829724] report_bug+0xd1/0x100
[128063.830327] handle_bug+0x35/0x80
[128063.830910] exc_invalid_op+0x14/0x70
[128063.831476] asm_exc_invalid_op+0x12/0x20
[128063.832042] RIP: 0010:create_pending_snapshot+0xa2a/0xfd0 [btrfs]
With 5.8 and older, I never got such failures on my test boxes.
Thanks.
>
> Thanks,
> Dennis
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
