Re: [Regression] Bug 216961 - Severe IO scheduling starvation issues with btrfs

[Thorsten Leemhuis]

Hi btrfs maintainers and developers.

I might be missing something, but it looks like the report was ignored.
Is there a reason for that?

FWIW, meanwhile another user showed up in the report that apparently is
affected by the same issue:

>  pmacedo 2023-02-07 12:47:31 UTC
> 
> This matches my experience on Debian with kernel from their unstable
> repository (6.1.4-1). I've rolled back to the current stable kernel
> from Bullseye (5.10.0-20-amd64, which according to the changelog is
> based on 5.10.158-2) about a week ago after finding this bug and the
> long IO stalls have disappeared.
> 
> Looks like Debian had 6.0 in backports, so I'll give it a try and
> report back.
> 
> [reply] [−] Comment 5 pmacedo 2023-02-07 19:22:55 UTC
> 
> From my testing, this seems to be between 5.19 and 6.0 - on 6.0 I've
> seen mkdir take up to 40 seconds, while on 5.19 it doesn't seem to
> ever go above half a second.
> 
> My setup is raid 6 for data, raid1c3 for metadata; in my case the
> stalls seem to happen more frequently after a large number of
> deletions and btrfs-transaction will appear to be very busy according
> to iotop, with everything else just stalling.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

#regzbot poke

On 26.01.23 12:17, Linux kernel regression tracking (Thorsten Leemhuis)
wrote:
> Hi, this is your Linux kernel regression tracker.
> 
> I noticed a regression report in bugzilla.kernel.org. As many (most?)
> kernel developer don't keep an eye on it, I decided to forward it by
> mail. Quoting from https://bugzilla.kernel.org/show_bug.cgi?id=216961 :
> 
>>  Wyatt Childers 2023-01-23 17:44:13 UTC
>>
>> There seems to be an issue with btrfs in Kernel 6 (first seen in at least 6.0.12-300.fc37.x86_64, possibly earlier) and still observed in 6.1 (6.1.5-200.fc37.x86_64).
>>
>> This has manifested in prolonged user space hangs. I first noticed this in internal tooling for my employer where simple IO operations like a trivial cp commands that typically take under 100ms (when run with many other concurrent IO operations of a similar ilk) are observing "scheduling starvation" being stalled in a disk sleep state for nearly a minute.
>>
>> This also seems to be manifesting in hangs to Kwin that correlate with btrfs usage and things as routine and trivial (even on high performance systems) as system updates https://bugs.kde.org/show_bug.cgi?id=463353
>>
>> I would also not be surprised if this behavior is responsible for things like this reddit thread: https://www.reddit.com/r/btrfs/comments/102or0t/btrfs_on_luks_whole_system_freezing_under_high_io/
>>
>> [reply] [−] Comment 1 Wyatt Childers 2023-01-23 17:57:47 UTC
>>
>> As additional context, here are some sample kernel traces (echo w > /proc/sysrq-trigger):
>>
>> Dec 16 14:10:02 localhost kernel: sysrq: Show Blocked State
>> Dec 16 14:10:02 localhost kernel: task:kworker/u64:6   state:D stack:    0 pid:2673507 ppid:     2 flags:0x00004000
>> Dec 16 14:10:02 localhost kernel: Workqueue: btrfs-worker btrfs_work_helper
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  ? __sbitmap_get_word+0x37/0x80
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  blk_mq_get_tag+0x10c/0x290
>> Dec 16 14:10:02 localhost kernel:  ? dequeue_task_stop+0x70/0x70
>> Dec 16 14:10:02 localhost kernel:  __blk_mq_alloc_requests+0x183/0x2b0
>> Dec 16 14:10:02 localhost kernel:  blk_mq_submit_bio+0x2b7/0x5b0
>> Dec 16 14:10:02 localhost kernel:  __submit_bio+0xf5/0x180
>> Dec 16 14:10:02 localhost kernel:  submit_bio_noacct_nocheck+0x20d/0x2a0
>> Dec 16 14:10:02 localhost kernel:  btrfs_submit_bio+0x17a/0x3d0
>> Dec 16 14:10:02 localhost kernel:  btrfs_work_helper+0x14b/0x380
>> Dec 16 14:10:02 localhost kernel:  process_one_work+0x1c7/0x380
>> Dec 16 14:10:02 localhost kernel:  worker_thread+0x4d/0x380
>> Dec 16 14:10:02 localhost kernel:  ? _raw_spin_lock_irqsave+0x23/0x50
>> Dec 16 14:10:02 localhost kernel:  ? rescuer_thread+0x380/0x380
>> Dec 16 14:10:02 localhost kernel:  kthread+0xe9/0x110
>> Dec 16 14:10:02 localhost kernel:  ? kthread_complete_and_exit+0x20/0x20
>> Dec 16 14:10:02 localhost kernel:  ret_from_fork+0x22/0x30
>> Dec 16 14:10:02 localhost kernel:  </TASK>
>> Dec 16 14:10:02 localhost kernel: task:cp              state:D stack:    0 pid:2422766 ppid:2410777 flags:0x00000002
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  ? btrfs_delayed_update_inode+0x102/0x1f0
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  folio_wait_bit_common+0x12d/0x3a0
>> Dec 16 14:10:02 localhost kernel:  ? filemap_alloc_folio+0xc0/0xc0
>> Dec 16 14:10:02 localhost kernel:  folio_wait_writeback+0x28/0x80
>> Dec 16 14:10:02 localhost kernel:  __filemap_fdatawait_range+0x7f/0x100
>> Dec 16 14:10:02 localhost kernel:  filemap_fdatawait_range+0xe/0x20
>> Dec 16 14:10:02 localhost kernel:  btrfs_wait_ordered_range+0x7a/0x120
>> Dec 16 14:10:02 localhost kernel:  btrfs_remap_file_range+0x139/0x550
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ovl_copyfile+0x15d/0x180 [overlay]
>> Dec 16 14:10:02 localhost kernel:  ovl_remap_file_range+0x6e/0xa0 [overlay]
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ioctl_file_clone+0x49/0xb0
>> Dec 16 14:10:02 localhost kernel:  do_vfs_ioctl+0x77/0x950
>> Dec 16 14:10:02 localhost kernel:  ? security_file_ioctl+0x3c/0x60
>> Dec 16 14:10:02 localhost kernel:  __x64_sys_ioctl+0x6e/0xd0
>> Dec 16 14:10:02 localhost kernel:  do_syscall_64+0x5b/0x80
>> Dec 16 14:10:02 localhost kernel:  ? syscall_exit_to_user_mode+0x17/0x40
>> Dec 16 14:10:02 localhost kernel:  ? do_syscall_64+0x67/0x80
>> Dec 16 14:10:02 localhost kernel:  ? syscall_exit_to_user_mode+0x17/0x40
>> Dec 16 14:10:02 localhost kernel:  ? do_syscall_64+0x67/0x80
>> Dec 16 14:10:02 localhost kernel:  ? do_user_addr_fault+0x1ef/0x690
>> Dec 16 14:10:02 localhost kernel:  ? do_syscall_64+0x67/0x80
>> Dec 16 14:10:02 localhost kernel:  ? exc_page_fault+0x70/0x170
>> Dec 16 14:10:02 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> Dec 16 14:10:02 localhost kernel: RIP: 0033:0x7f07d2d7dbaf
>> Dec 16 14:10:02 localhost kernel: RSP: 002b:00007ffc4ba5bf40 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> Dec 16 14:10:02 localhost kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f07d2d7dbaf
>> Dec 16 14:10:02 localhost kernel: RDX: 0000000000000003 RSI: 0000000040049409 RDI: 0000000000000004
>> Dec 16 14:10:02 localhost kernel: RBP: 00007ffc4ba5d8cc R08: 0000000000000001 R09: 00000000000001a4
>> Dec 16 14:10:02 localhost kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc4ba5c3e0
>> Dec 16 14:10:02 localhost kernel: R13: 0000000000000001 R14: 0000000000000014 R15: 00007ffc4ba5c7b0
>> Dec 16 14:10:02 localhost kernel:  </TASK>
>> Dec 16 14:10:02 localhost kernel: task:cp              state:D stack:    0 pid:2422815 ppid:2419287 flags:0x00000002
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  ? btrfs_dirty_inode+0x91/0xe0
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  folio_wait_bit_common+0x12d/0x3a0
>> Dec 16 14:10:02 localhost kernel:  ? filemap_alloc_folio+0xc0/0xc0
>> Dec 16 14:10:02 localhost kernel:  folio_wait_writeback+0x28/0x80
>> Dec 16 14:10:02 localhost kernel:  __filemap_fdatawait_range+0x7f/0x100
>> Dec 16 14:10:02 localhost kernel:  filemap_fdatawait_range+0xe/0x20
>> Dec 16 14:10:02 localhost kernel:  btrfs_wait_ordered_range+0x7a/0x120
>> Dec 16 14:10:02 localhost kernel:  btrfs_remap_file_range+0x139/0x550
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ovl_copyfile+0x15d/0x180 [overlay]
>> Dec 16 14:10:02 localhost kernel:  ovl_remap_file_range+0x6e/0xa0 [overlay]
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ioctl_file_clone+0x49/0xb0
>> Dec 16 14:10:02 localhost kernel:  do_vfs_ioctl+0x77/0x950
>> Dec 16 14:10:02 localhost kernel:  __x64_sys_ioctl+0x6e/0xd0
>> Dec 16 14:10:02 localhost kernel:  do_syscall_64+0x5b/0x80
>> Dec 16 14:10:02 localhost kernel:  ? exc_page_fault+0x70/0x170
>> Dec 16 14:10:02 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> Dec 16 14:10:02 localhost kernel: RIP: 0033:0x7f1e8dc22baf
>> Dec 16 14:10:02 localhost kernel: RSP: 002b:00007ffd65479d50 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> Dec 16 14:10:02 localhost kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f1e8dc22baf
>> Dec 16 14:10:02 localhost kernel: RDX: 0000000000000003 RSI: 0000000040049409 RDI: 0000000000000004
>> Dec 16 14:10:02 localhost kernel: RBP: 00007ffd6547b8cc R08: 0000000000000001 R09: 00000000000001a4
>> Dec 16 14:10:02 localhost kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd6547a1f0
>> Dec 16 14:10:02 localhost kernel: R13: 0000000000000001 R14: 0000000000000014 R15: 00007ffd6547a5c0
>> Dec 16 14:10:02 localhost kernel:  </TASK>
>> Dec 16 14:10:02 localhost kernel: task:cp              state:D stack:    0 pid:2422818 ppid:2421995 flags:0x00000002
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  folio_wait_bit_common+0x12d/0x3a0
>> Dec 16 14:10:02 localhost kernel:  ? filemap_alloc_folio+0xc0/0xc0
>> Dec 16 14:10:02 localhost kernel:  folio_wait_writeback+0x28/0x80
>> Dec 16 14:10:02 localhost kernel:  __filemap_fdatawait_range+0x7f/0x100
>> Dec 16 14:10:02 localhost kernel:  filemap_fdatawait_range+0xe/0x20
>> Dec 16 14:10:02 localhost kernel:  btrfs_wait_ordered_range+0x7a/0x120
>> Dec 16 14:10:02 localhost kernel:  btrfs_remap_file_range+0x139/0x550
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ovl_copyfile+0x15d/0x180 [overlay]
>> Dec 16 14:10:02 localhost kernel:  ovl_remap_file_range+0x6e/0xa0 [overlay]
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ioctl_file_clone+0x49/0xb0
>> Dec 16 14:10:02 localhost kernel:  do_vfs_ioctl+0x77/0x950
>> Dec 16 14:10:02 localhost kernel:  __x64_sys_ioctl+0x6e/0xd0
>> Dec 16 14:10:02 localhost kernel:  do_syscall_64+0x5b/0x80
>> Dec 16 14:10:02 localhost kernel:  ? syscall_exit_to_user_mode+0x17/0x40
>> Dec 16 14:10:02 localhost kernel:  ? do_syscall_64+0x67/0x80
>> Dec 16 14:10:02 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> Dec 16 14:10:02 localhost kernel: RIP: 0033:0x7ffa2a678baf
>> Dec 16 14:10:02 localhost kernel: RSP: 002b:00007ffe77c03de0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> Dec 16 14:10:02 localhost kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007ffa2a678baf
>> Dec 16 14:10:02 localhost kernel: RDX: 0000000000000003 RSI: 0000000040049409 RDI: 0000000000000004
>> Dec 16 14:10:02 localhost kernel: RBP: 00007ffe77c058cc R08: 0000000000000001 R09: 00000000000001a4
>> Dec 16 14:10:02 localhost kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe77c04280
>> Dec 16 14:10:02 localhost kernel: R13: 0000000000000001 R14: 0000000000000014 R15: 00007ffe77c04650
>> Dec 16 14:10:02 localhost kernel:  </TASK>
>> Dec 16 14:10:02 localhost kernel: task:cp              state:D stack:    0 pid:2422821 ppid:2420167 flags:0x00000002
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  ? _raw_spin_unlock_irqrestore+0x23/0x40
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  folio_wait_bit_common+0x12d/0x3a0
>> Dec 16 14:10:02 localhost kernel:  ? filemap_alloc_folio+0xc0/0xc0
>> Dec 16 14:10:02 localhost kernel:  folio_wait_writeback+0x28/0x80
>> Dec 16 14:10:02 localhost kernel:  __filemap_fdatawait_range+0x7f/0x100
>> Dec 16 14:10:02 localhost kernel:  filemap_fdatawait_range+0xe/0x20
>> Dec 16 14:10:02 localhost kernel:  btrfs_wait_ordered_range+0x7a/0x120
>> Dec 16 14:10:02 localhost kernel:  btrfs_remap_file_range+0x139/0x550
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ovl_copyfile+0x15d/0x180 [overlay]
>> Dec 16 14:10:02 localhost kernel:  ovl_remap_file_range+0x6e/0xa0 [overlay]
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ioctl_file_clone+0x49/0xb0
>> Dec 16 14:10:02 localhost kernel:  do_vfs_ioctl+0x77/0x950
>> Dec 16 14:10:02 localhost kernel:  ? security_file_ioctl+0x3c/0x60
>> Dec 16 14:10:02 localhost kernel:  __x64_sys_ioctl+0x6e/0xd0
>> Dec 16 14:10:02 localhost kernel:  do_syscall_64+0x5b/0x80
>> Dec 16 14:10:02 localhost kernel:  ? do_syscall_64+0x67/0x80
>> Dec 16 14:10:02 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> Dec 16 14:10:02 localhost kernel: RIP: 0033:0x7fafe34febaf
>> Dec 16 14:10:02 localhost kernel: RSP: 002b:00007fff79bee930 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> Dec 16 14:10:02 localhost kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fafe34febaf
>> Dec 16 14:10:02 localhost kernel: RDX: 0000000000000003 RSI: 0000000040049409 RDI: 0000000000000004
>> Dec 16 14:10:02 localhost kernel: RBP: 00007fff79bef8f6 R08: 0000000000000001 R09: 00000000000001a4
>> Dec 16 14:10:02 localhost kernel: R10: 0000000000000004 R11: 0000000000000246 R12: 00007fff79beedd0
>> Dec 16 14:10:02 localhost kernel: R13: 0000000000000001 R14: 0000000000000002 R15: 00007fff79bef1a0
>> Dec 16 14:10:02 localhost kernel:  </TASK>
>> Dec 16 14:10:02 localhost kernel: task:cp              state:D stack:    0 pid:2422911 ppid:2401445 flags:0x00000002
>> Dec 16 14:10:02 localhost kernel: Call Trace:
>> Dec 16 14:10:02 localhost kernel:  <TASK>
>> Dec 16 14:10:02 localhost kernel:  __schedule+0x332/0x12c0
>> Dec 16 14:10:02 localhost kernel:  ? __btrfs_end_transaction+0xf8/0x240
>> Dec 16 14:10:02 localhost kernel:  schedule+0x5d/0xe0
>> Dec 16 14:10:02 localhost kernel:  io_schedule+0x42/0x70
>> Dec 16 14:10:02 localhost kernel:  folio_wait_bit_common+0x12d/0x3a0
>> Dec 16 14:10:02 localhost kernel:  ? filemap_alloc_folio+0xc0/0xc0
>> Dec 16 14:10:02 localhost kernel:  folio_wait_writeback+0x28/0x80
>> Dec 16 14:10:02 localhost kernel:  __filemap_fdatawait_range+0x7f/0x100
>> Dec 16 14:10:02 localhost kernel:  filemap_fdatawait_range+0xe/0x20
>> Dec 16 14:10:02 localhost kernel:  btrfs_wait_ordered_range+0x7a/0x120
>> Dec 16 14:10:02 localhost kernel:  btrfs_remap_file_range+0x139/0x550
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ovl_copyfile+0x15d/0x180 [overlay]
>> Dec 16 14:10:02 localhost kernel:  ovl_remap_file_range+0x6e/0xa0 [overlay]
>> Dec 16 14:10:02 localhost kernel:  do_clone_file_range+0xe9/0x230
>> Dec 16 14:10:02 localhost kernel:  vfs_clone_file_range+0x4d/0x140
>> Dec 16 14:10:02 localhost kernel:  ioctl_file_clone+0x49/0xb0
>> Dec 16 14:10:02 localhost kernel:  do_vfs_ioctl+0x77/0x950
>> Dec 16 14:10:02 localhost kernel:  __x64_sys_ioctl+0x6e/0xd0
>> Dec 16 14:10:02 localhost kernel:  do_syscall_64+0x5b/0x80
>> Dec 16 14:10:02 localhost kernel:  ? exc_page_fault+0x70/0x170
>> Dec 16 14:10:02 localhost kernel:  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> Dec 16 14:10:02 localhost kernel: RIP: 0033:0x7ff280aeebaf
>> Dec 16 14:10:02 localhost kernel: RSP: 002b:00007ffdbfa595c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
>> Dec 16 14:10:02 localhost kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007ff280aeebaf
>> Dec 16 14:10:02 localhost kernel: RDX: 0000000000000003 RSI: 0000000040049409 RDI: 0000000000000004
>> Dec 16 14:10:02 localhost kernel: RBP: 00007ffdbfa5a8cc R08: 0000000000000001 R09: 00000000000001a4
>> Dec 16 14:10:02 localhost kernel: R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdbfa59a60
>> Dec 16 14:10:02 localhost kernel: R13: 0000000000000001 R14: 0000000000000014 R15: 00007ffdbfa59e30
>> Dec 16 14:10:02 localhost kernel:  </TASK>
> See the ticket for more details.
> 
> 
> [TLDR for the rest of this mail: I'm adding this report to the list of
> tracked Linux kernel regressions; the text you find below is based on a
> few templates paragraphs you might have encountered already in similar
> form.]
> 
> BTW, let me use this mail to also add the report to the list of tracked
> regressions to ensure it's doesn't fall through the cracks (I for now
> assume it was introduced between v5.19..v6.0, even if I don't know for
> sure ):
> 
> #regzbot introduced: v5.19..v6.0
> https://bugzilla.kernel.org/show_bug.cgi?id=216961
> #regzbot title: btrfs: severe IO scheduling starvation issues with btrfs
> #regzbot ignore-activity
> 
> This isn't a regression? This issue or a fix for it are already
> discussed somewhere else? It was fixed already? You want to clarify when
> the regression started to happen? Or point out I got the title or
> something else totally wrong? Then just reply and tell me -- ideally
> while also telling regzbot about it, as explained by the page listed in
> the footer of this mail.
> 
> Developers: When fixing the issue, remember to add 'Link:' tags pointing
> to the report (e.g. the buzgzilla ticket and maybe this mail as well, if
> this thread sees some discussion). See page linked in footer for details.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
> https://linux-regtracking.leemhuis.info/about/#tldr
> If I did something stupid, please tell me, as explained on that page.