Re: page allocation stall in kernel 4.9 when copying files from one btrfs hdd to another

[Xin Zhou]

Hi David,

It has GFP_NOFS flags, according to definition,
the issue might have happened during initial DISK/IO.

By the way, did you get a chance to dump the meminfo and run "top" before the system hang?
It seems more info about the system running state needed to know the issue. Thanks.

Xin

Â

Sent:ÂTuesday, December 13, 2016 at 9:11 AM
From:Â"David Arendt" <admin@xxxxxxxxx>
To:Âlinux-btrfs@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Subject:Âpage allocation stall in kernel 4.9 when copying files from one btrfs hdd to another
Hi,

I receive the following page allocation stall while copying lots of
large files from one btrfs hdd to another.

Dec 13 13:04:29 server kernel: kworker/u16:8: page allocation stalls for
12260ms, order:0, mode:0x2400840(GFP_NOFS|__GFP_NOFAIL)
Dec 13 13:04:29 server kernel: CPU: 0 PID: 24959 Comm: kworker/u16:8
Tainted: P O 4.9.0 #1
Dec 13 13:04:29 server kernel: Hardware name: ASUS All Series/H87M-PRO,
BIOS 2102 10/28/2014
Dec 13 13:04:29 server kernel: Workqueue: btrfs-extent-refs
btrfs_extent_refs_helper
Dec 13 13:04:29 server kernel: 0000000000000000 ffffffff813f3a59
ffffffff81976b28 ffffc90011093750
Dec 13 13:04:29 server kernel: ffffffff81114fc1 02400840f39b6bc0
ffffffff81976b28 ffffc900110936f8
Dec 13 13:04:29 server kernel: ffff880700000010 ffffc90011093760
ffffc90011093710 0000000002400840
Dec 13 13:04:29 server kernel: Call Trace:
Dec 13 13:04:29 server kernel: [<ffffffff813f3a59>] ? dump_stack+0x46/0x5d
Dec 13 13:04:29 server kernel: [<ffffffff81114fc1>] ?
warn_alloc+0x111/0x130
Dec 13 13:04:33 server kernel: [<ffffffff81115c38>] ?
__alloc_pages_nodemask+0xbe8/0xd30
Dec 13 13:04:33 server kernel: [<ffffffff8110de74>] ?
pagecache_get_page+0xe4/0x230
Dec 13 13:04:33 server kernel: [<ffffffff81323a8b>] ?
alloc_extent_buffer+0x10b/0x400
Dec 13 13:04:33 server kernel: [<ffffffff812ef8c5>] ?
btrfs_alloc_tree_block+0x125/0x560
Dec 13 13:04:33 server kernel: [<ffffffff8132442f>] ?
read_extent_buffer_pages+0x21f/0x280
Dec 13 13:04:33 server kernel: [<ffffffff812d81f1>] ?
__btrfs_cow_block+0x141/0x580
Dec 13 13:04:33 server kernel: [<ffffffff812d87b0>] ?
btrfs_cow_block+0x100/0x150
Dec 13 13:04:33 server kernel: [<ffffffff812dc1d9>] ?
btrfs_search_slot+0x1e9/0x9c0
Dec 13 13:04:33 server kernel: [<ffffffff8131ead2>] ?
__set_extent_bit+0x512/0x550
Dec 13 13:04:33 server kernel: [<ffffffff812e1ab5>] ?
lookup_inline_extent_backref+0xf5/0x5e0
Dec 13 13:04:34 server kernel: [<ffffffff8131f0a4>] ?
set_extent_bit+0x24/0x30
Dec 13 13:04:34 server kernel: [<ffffffff812e4334>] ?
update_block_group.isra.34+0x114/0x380
Dec 13 13:04:34 server kernel: [<ffffffff812e4694>] ?
__btrfs_free_extent.isra.35+0xf4/0xd20
Dec 13 13:04:34 server kernel: [<ffffffff8134d561>] ?
btrfs_merge_delayed_refs+0x61/0x5d0
Dec 13 13:04:34 server kernel: [<ffffffff812e8bd2>] ?
__btrfs_run_delayed_refs+0x902/0x10a0
Dec 13 13:04:34 server kernel: [<ffffffff812ec0f0>] ?
btrfs_run_delayed_refs+0x90/0x2a0
Dec 13 13:04:34 server kernel: [<ffffffff812ec384>] ?
delayed_ref_async_start+0x84/0xa0
Dec 13 13:04:34 server kernel: [<ffffffff8109c16d>] ?
process_one_work+0x11d/0x3b0
Dec 13 13:04:34 server kernel: [<ffffffff8109c442>] ?
worker_thread+0x42/0x4b0
Dec 13 13:04:34 server kernel: [<ffffffff8109c400>] ?
process_one_work+0x3b0/0x3b0
Dec 13 13:04:34 server kernel: [<ffffffff8109c400>] ?
process_one_work+0x3b0/0x3b0
Dec 13 13:04:34 server kernel: [<ffffffff8108ba5e>] ?
do_group_exit+0x2e/0xa0
Dec 13 13:04:34 server kernel: [<ffffffff810a12d9>] ? kthread+0xb9/0xd0
Dec 13 13:04:34 server kernel: [<ffffffff810a1220>] ?
kthread_park+0x50/0x50
Dec 13 13:04:34 server kernel: [<ffffffff81798cd2>] ?
ret_from_fork+0x22/0x30
Dec 13 13:04:34 server kernel: Mem-Info:
Dec 13 13:04:34 server kernel: active_anon:20 inactive_anon:34
isolated_anon:0\x0a active_file:7370032 inactive_file:450105
isolated_file:320\x0a unevictable:0 dirty:522748 writeback:189
unstable:0\x0a slab_reclaimable:178255 slab_unreclaimable:124617\x0a
mapped:4236 shmem:0 pagetables:1163 bounce:0\x0a free:38224 free_pcp:241
free_cma:0
Dec 13 13:04:34 server kernel: Node 0 active_anon:80kB
inactive_anon:136kB active_file:29480128kB inactive_file:1800420kB
unevictable:0kB isolated(anon):0kB isolated(file):1280kB mapped:16944kB
dirty:2090992kB writeback:756kB shmem:0kB writeback_tmp:0kB unstable:0kB
pages_scanned:258821 all_unreclaimable? no
Dec 13 13:04:34 server kernel: DMA free:15868kB min:8kB low:20kB
high:32kB active_anon:0kB inactive_anon:0kB active_file:0kB
inactive_file:0kB unevictable:0kB writepending:0kB present:15976kB
managed:15892kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:24kB
kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:0kB local_pcp:0kB
free_cma:0kB
Dec 13 13:04:34 server kernel: lowmem_reserve[]: 0 3428 32019 32019
Dec 13 13:04:34 server kernel: DMA32 free:116800kB min:2448kB low:5956kB
high:9464kB active_anon:0kB inactive_anon:0kB active_file:3087928kB
inactive_file:191336kB unevictable:0kB writepending:221828kB
present:3590832kB managed:3513936kB mlocked:0kB slab_reclaimable:93252kB
slab_unreclaimable:20520kB kernel_stack:48kB pagetables:212kB bounce:0kB
free_pcp:4kB local_pcp:0kB free_cma:0kB
Dec 13 13:04:34 server kernel: lowmem_reserve[]: 0 0 0 0
Dec 13 13:04:34 server kernel: DMA: 1*4kB (U) 1*8kB (U) 1*16kB (U)
1*32kB (U) 1*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U)
1*2048kB (M) 3*4096kB (M) = 15868kB
Dec 13 13:04:34 server kernel: DMA32: 940*4kB (UME) 4006*8kB (UME)
3308*16kB (UME) 791*32kB (UME) 41*64kB (UE) 1*128kB (U) 0*256kB 0*512kB
0*1024kB 0*2048kB 0*4096kB = 116800kB
Dec 13 13:04:34 server kernel: Normal: 75*4kB (E) 192*8kB (UE) 94*16kB
(UME) 57*32kB (U) 33*64kB (UM) 16*128kB (UM) 10*256kB (UM) 4*512kB (U)
0*1024kB 1*2048kB (U) 1*4096kB (U) = 20076kB
Dec 13 13:04:34 server kernel: Node 0 hugepages_total=0 hugepages_free=0
hugepages_surp=0 hugepages_size=2048kB
Dec 13 13:04:34 server kernel: 7820441 total pagecache pages
Dec 13 13:04:34 server kernel: 69 pages in swap cache
Dec 13 13:04:34 server kernel: Swap cache stats: add 60282, delete
60213, find 249865/258319
Dec 13 13:04:34 server kernel: Free swap = 62482976kB
Dec 13 13:04:34 server kernel: Total swap = 62522692kB
Dec 13 13:04:34 server kernel: 8364614 pages RAM
Dec 13 13:04:34 server kernel: 0 pages HighMem/MovableOnly
Dec 13 13:04:34 server kernel: 162971 pages reserved

Has anyone any idea what could go wrong here ?

Thanks in advance,

David Arendt

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