Re: PROBLEM: bcache related kernel BUG() since Linux 5.12

[Thorsten Knabe <linux@thorsten-knabe.de>]

Hello Coly.

On 6/1/21 5:34 PM, Coly Li wrote:
> On 5/31/21 5:37 PM, Rolf Fokkens wrote:
>> Same here, more details: https://bugzilla.redhat.com/show_bug.cgi?id=1965809
> 
> Could you please try these attached patches ? I'd like to have more
> confirmation before submitting to Jens.

Running 5.12.8 + your v5 patches for a few hours now on that degraded
RAID-6 system without any issues. If anything changes, I'll let you know.

Thorsten
> 
> Thanks.
> 
> Coly Li
> 
> 
> 
>>
>> On 5/15/21 9:06 PM, Thorsten Knabe wrote:
>>> Hello.
>>>
>>> Starting with Linux 5.12 bcache triggers a BUG() after a few minutes of
>>> usage.
>>>
>>> Linux up to 5.11.x is not affected by this bug.
>>>
>>> Environment:
>>> - Debian 10 AMD 64
>>> - Kernel 5.12 - 5.12.4
>>> - Filesystem ext4
>>> - Backing device: degraded software RAID-6 (MD) with 3 of 4 disks active
>>>   (unsure if the degraded RAID-6 has an effect or not)
>>> - Cache device: Single SSD
>>>
>>> Kernel log:
>>>
>>> May 12 20:22:24 tek04 kernel: nr_vecs=472
>>> May 12 20:22:24 tek04 kernel: ------------[ cut here ]------------
>>> May 12 20:22:24 tek04 kernel: kernel BUG at block/bio.c:53!
>>> May 12 20:22:24 tek04 kernel: invalid opcode: 0000 [#1] PREEMPT SMP PTI
>>> May 12 20:22:24 tek04 kernel: CPU: 1 PID: 1670 Comm: grep Tainted: G
>>>       I       5.12.3 #2
>>> May 12 20:22:24 tek04 kernel: Hardware name: To Be Filled By O.E.M. To
>>> Be Filled By O.E.M./X58 Deluxe, BIOS P2.20 10/30/2009
>>> May 12 20:22:24 tek04 kernel: RIP: 0010:biovec_slab.cold.45+0xf/0x11
>>> May 12 20:22:24 tek04 kernel: Code: b3 ae ff 89 c6 48 c7 c7 30 82 21 82
>>> e8 03 81 fe ff b8 b6 ff ff ff e9 3d bc ae ff 0f b7 f7 48 c7 c7 c4 82 21
>>> 82 e8 ea 80 fe ff <0f> 0b 49 8b b4 24 d0 00 00 00 48 c7 c7 40 84 21 82
>>> e8 d4 80 fe ff
>>> May 12 20:22:24 tek04 kernel: RSP: 0018:ffffc9000274b730 EFLAGS: 00010292
>>> May 12 20:22:24 tek04 kernel: RAX: 000000000000000b RBX:
>>> ffffc9000274b764 RCX: 0000000000000000
>>> May 12 20:22:24 tek04 kernel: bch_count_backing_io_errors: 1 callbacks
>>> suppressed
>>> May 12 20:22:24 tek04 kernel: bcache: bch_count_backing_io_errors() md1:
>>> Read-ahead I/O failed on backing device, ignore
>>> May 12 20:22:24 tek04 kernel: RDX: ffff888333c5e400 RSI:
>>> ffff888333c57480 RDI: ffff888333c57480
>>> May 12 20:22:24 tek04 kernel: RBP: 0000000000000800 R08:
>>> 0000000000000000 R09: c0000000ffffdfff
>>> May 12 20:22:24 tek04 kernel: R10: ffffc9000274b580 R11:
>>> ffffc9000274b578 R12: ffff8881170f0118
>>> May 12 20:22:24 tek04 kernel: R13: ffff888109911b00 R14:
>>> ffff8881170f00d0 R15: 0000000000000800
>>> May 12 20:22:24 tek04 kernel: FS:  00007f3a1ca7cb80(0000)
>>> GS:ffff888333c40000(0000) knlGS:0000000000000000
>>> May 12 20:22:24 tek04 kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
>>> 0000000080050033
>>> May 12 20:22:24 tek04 kernel: CR2: 00005628963f4fd0 CR3:
>>> 000000016c43c000 CR4: 00000000000006e0
>>> May 12 20:22:24 tek04 kernel: Call Trace:
>>> May 12 20:22:24 tek04 kernel:  bvec_alloc+0x22/0x90
>>> May 12 20:22:24 tek04 kernel:  bio_alloc_bioset+0x176/0x230
>>> May 12 20:22:24 tek04 kernel:  cached_dev_cache_miss+0x1a8/0x300
>>> May 12 20:22:24 tek04 kernel:  cache_lookup_fn+0x110/0x2e0
>>> May 12 20:22:24 tek04 kernel:  ? bch_ptr_invalid+0x10/0x10
>>> May 12 20:22:24 tek04 kernel:  ? bch_btree_iter_next_filter+0x1af/0x2d0
>>> May 12 20:22:24 tek04 kernel:  ? cache_lookup+0x190/0x190
>>> May 12 20:22:24 tek04 kernel:  bch_btree_map_keys_recurse+0x69/0x160
>>> May 12 20:22:24 tek04 kernel:  ? __bch_bset_search+0x315/0x440
>>> May 12 20:22:24 tek04 kernel:  ? downgrade_write+0xb0/0xb0
>>> May 12 20:22:24 tek04 kernel:  ? cache_lookup+0x190/0x190
>>> May 12 20:22:24 tek04 kernel:  bch_btree_map_keys_recurse+0xcf/0x160
>>> May 12 20:22:24 tek04 kernel:  ? raid5_make_request+0x5c4/0xaa0
>>> May 12 20:22:24 tek04 kernel:  ? recalibrate_cpu_khz+0x10/0x10
>>> May 12 20:22:24 tek04 kernel:  ? kmem_cache_alloc+0x30/0x400
>>> May 12 20:22:24 tek04 kernel:  ? rwsem_wake.isra.11+0x80/0x80
>>> May 12 20:22:24 tek04 kernel:  bch_btree_map_keys+0xf2/0x140
>>> May 12 20:22:24 tek04 kernel:  ? cache_lookup+0x190/0x190
>>> May 12 20:22:24 tek04 kernel:  cache_lookup+0xb1/0x190
>>> May 12 20:22:24 tek04 kernel:  cached_dev_submit_bio+0x9ab/0xc90
>>> May 12 20:22:24 tek04 kernel:  ? submit_bio_checks+0x197/0x4a0
>>> May 12 20:22:24 tek04 kernel:  ? kmem_cache_alloc+0x3b7/0x400
>>> May 12 20:22:24 tek04 kernel:  submit_bio_noacct+0x10e/0x4c0
>>> May 12 20:22:24 tek04 kernel:  submit_bio+0x2e/0x160
>>> May 12 20:22:24 tek04 kernel:  ? xa_load+0x66/0x70
>>> May 12 20:22:24 tek04 kernel:  ? bio_add_page+0x2f/0x70
>>> May 12 20:22:24 tek04 kernel:  ext4_mpage_readpages+0x1ae/0xa00
>>> May 12 20:22:24 tek04 kernel:  ? __mod_lruvec_state+0x29/0x60
>>> May 12 20:22:24 tek04 kernel:  read_pages+0x78/0x1d0
>>> May 12 20:22:24 tek04 kernel:  page_cache_ra_unbounded+0x127/0x1b0
>>> May 12 20:22:24 tek04 kernel:  filemap_get_pages+0x1d0/0x4a0
>>> May 12 20:22:24 tek04 kernel:  filemap_read+0x91/0x2d0
>>> May 12 20:22:24 tek04 kernel:  new_sync_read+0x103/0x180
>>> May 12 20:22:24 tek04 kernel:  vfs_read+0x11b/0x1b0
>>> May 12 20:22:24 tek04 kernel:  ksys_read+0x55/0xd0
>>> May 12 20:22:24 tek04 kernel:  do_syscall_64+0x33/0x80
>>> May 12 20:22:24 tek04 kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae
>>> May 12 20:22:24 tek04 kernel: RIP: 0033:0x7f3a1cb89461
>>> May 12 20:22:24 tek04 kernel: Code: fe ff ff 50 48 8d 3d fe d0 09 00 e8
>>> e9 03 02 00 66 0f 1f 84 00 00 00 00 00 48 8d 05 99 62 0d 00 8b 00 85 c0
>>> 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 c3 66 0f 1f 44 00 00 41 54
>>> 49 89 d4 55 48
>>> May 12 20:22:24 tek04 kernel: RSP: 002b:00007fff4052fff8 EFLAGS:
>>> 00000246 ORIG_RAX: 0000000000000000
>>> May 12 20:22:24 tek04 kernel: RAX: ffffffffffffffda RBX:
>>> 0000000000018000 RCX: 00007f3a1cb89461
>>> May 12 20:22:24 tek04 kernel: RDX: 0000000000018000 RSI:
>>> 000055ff0d01a000 RDI: 0000000000000004
>>> May 12 20:22:24 tek04 kernel: RBP: 0000000000018000 R08:
>>> 0000000000000002 R09: 000055ff0d0194b0
>>> May 12 20:22:24 tek04 kernel: R10: 0000000000000000 R11:
>>> 0000000000000246 R12: 000055ff0d01a000
>>> May 12 20:22:24 tek04 kernel: R13: 0000000000000004 R14:
>>> 000055ff0d0194b0 R15: 0000000000000004
>>> May 12 20:22:24 tek04 kernel: Modules linked in: cmac bnep
>>> intel_powerclamp snd_hda_codec_realtek snd_hda_codec_generic btusb
>>> ledtrig_audio snd_hda_codec_hdmi btrtl kvm_intel snd_hda_intel btbcm
>>> snd_intel_dspcfg btintel kvm snd_hda_codec irqbypass bluetooth serio_raw
>>> pcspkr hfcpci snd_hda_core iTCO_wdt evdev input_leds joydev sg snd_hwdep
>>> intel_pmc_bxt ecdh_generic rfkill iTCO_vendor_support mISDN_core ecc
>>> snd_pcm snd_timer tiny_power_button snd soundcore button i7core_edac
>>> acpi_cpufreq wmi nft_counter nf_log_ipv6 nf_log_ipv
>>> May 12 20:22:24 tek04 kernel: ---[ end trace 9a03f30c7b4aa246 ]---
>>> May 12 20:22:25 tek04 kernel: RIP: 0010:biovec_slab.cold.45+0xf/0x11
>>> May 12 20:22:25 tek04 kernel: Code: b3 ae ff 89 c6 48 c7 c7 30 82 21 82
>>> e8 03 81 fe ff b8 b6 ff ff ff e9 3d bc ae ff 0f b7 f7 48 c7 c7 c4 82 21
>>> 82 e8 ea 80 fe ff <0f> 0b 49 8b b4 24 d0 00 00 00 48 c7 c7 40 84 21 82
>>> e8 d4 80 fe ff
>>> May 12 20:22:25 tek04 kernel: RSP: 0018:ffffc9000274b730 EFLAGS: 00010292
>>> May 12 20:22:25 tek04 kernel: RAX: 000000000000000b RBX:
>>> ffffc9000274b764 RCX: 0000000000000000
>>> May 12 20:22:25 tek04 kernel: RDX: ffff888333c5e400 RSI:
>>> ffff888333c57480 RDI: ffff888333c57480
>>> May 12 20:22:25 tek04 kernel: RBP: 0000000000000800 R08:
>>> 0000000000000000 R09: c0000000ffffdfff
>>> May 12 20:22:25 tek04 kernel: R10: ffffc9000274b580 R11:
>>> ffffc9000274b578 R12: ffff8881170f0118
>>> May 12 20:22:25 tek04 kernel: R13: ffff888109911b00 R14:
>>> ffff8881170f00d0 R15: 0000000000000800
>>> May 12 20:22:25 tek04 kernel: FS:  00007f3a1ca7cb80(0000)
>>> GS:ffff888333c40000(0000) knlGS:0000000000000000
>>> May 12 20:22:25 tek04 kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
>>> 0000000080050033
>>> May 12 20:22:25 tek04 kernel: CR2: 00005628963f4fd0 CR3:
>>> 000000016c43c000 CR4: 00000000000006e0
>>>
>>> A printk has been added to line 52 of block/bio.c to dump the nr_vecs
>>> variable to the kernel log before the BUG(). Obviously nr_vecs (472
>>> logged) is bigger than expected by bvec_alloc/bio_alloc_bioset (max
>>> 256), which finally triggers the BUG().
>>>
>>> Removing the BUG() from line 52 of block/bio.c, thus basically restoring
>>> the Linux 5.11.x behavior of bvec_alloc/bio_alloc_bioset to just return
>>> NULL, when nr_vecs is too big seems to resolve the issue.
>>>
>>> Regards
>>> Thorsten
>>>
> 


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