Re: bisected: btrfs dedupe regression in v5.11-rc1: 3078d85c9a10 vfs: verify source area in vfs_dedupe_file_range_one()

Zygo Blaxell
2022-06-21T05:08:22Z

On Mon, Jun 13, 2022 at 08:38:52AM +0000, Libor Klepáč wrote:
> Hi,
> any news on this?

No news yet. It is near the top of my todo list, but the top of
my todo list is a highly contended place.

I did run a KCSAN audit on 5.18 and while it did find some btrfs problems,
it didn't find anything relevant to this bug. 5.4 seems not to have
the bug, but 5.4 comes with a ~30% performance drop compared to 5.10
(and I didn't test it long enough to say that 5.4 really has no bug).

> We have been running beesd in single thread as you suggested in
> https://github.com/Zygo/bees/issues/215#issuecomment-1104614791
>
> without kernel lock for almost two month on kernel 5.11 (don't know
> exact version, it's in ubuntu 20.04).
>
> We have recently switched to kernel 5.15 and started to use it at
> another customer too
>
> I don't know exact kernel version, it's Ubuntu 20.04 kernel:
> uname says
> Linux nakivo 5.15.0-33-generic #34~20.04.1-Ubuntu SMP Thu May 19
> 15:51:16 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
>
> Package version: 5.15.0-33.34~20.04.1
>
> Only problem is, that bees cannot keep up with data that are beiing
> added to system via nakivo backup app.
> htop says, that beesd runs around 8-20MB/s.
> System can do IO around 400-500MB/s , it's dedicated Dell R540 with
> hardware raid on Nearline SAS drives.
>
> Is kernel 5.15 safer for multi thread mode in beesd?

Unfortunately no. The range of kernels with the bug runs from at least
5.6 through 5.18, and probably kernels outside of that range as well.

> Thanks,
> Libor
>
>
>
> On Pá, 2021-12-10 at 13:34 -0500, Zygo Blaxell wrote:
> > I've been getting deadlocks in dedupe on btrfs since kernel 5.11, and
> > some bees users have reported it as well.  I bisected to this commit:
> >
> >         3078d85c9a10 vfs: verify source area in
> > vfs_dedupe_file_range_one()
> >
> > These kernels work for at least 18 hours:
> >
> >         5.10.83 (months)
> >         5.11.22 with 3078d85c9a10 reverted (36 hours)
> >         btrfs misc-next 66dc4de326b0 with 3078d85c9a10 reverted
> >
> > These kernels lock up in 3 hours or less:
> >
> >         5.11.22
> >         5.12.19
> >         5.14.21
> >         5.15.6
> >         btrfs for-next 279373dee83e
> >
> > All of the failing kernels include this commit, none of the non-
> > failing
> > kernels include the commit.
> >
> > Kernel logs from the lockup:
> >
> >         [19647.696042][ T3721] sysrq: Show Blocked State
> >         [19647.697024][ T3721] task:btrfs-transacti state:D stack:
> > 0 pid: 6161 ppid:     2 flags:0x00004000
> >         [19647.698203][ T3721] Call Trace:
> >         [19647.698608][ T3721]  __schedule+0x388/0xaf0
> >         [19647.699125][ T3721]  schedule+0x68/0xe0
> >         [19647.699615][ T3721]  btrfs_commit_transaction+0x97c/0xbf0
> >         [19647.700276][ T3721]  ? start_transaction+0xd5/0x6f0
> >         [19647.700897][ T3721]  ? do_wait_intr_irq+0xd0/0xd0
> >         [19647.701507][ T3721]  transaction_kthread+0x138/0x1b0
> >         [19647.702154][ T3721]  kthread+0x151/0x170
> >         [19647.702651][ T3721]  ?
> > btrfs_cleanup_transaction.isra.0+0x620/0x620
> >         [19647.703404][ T3721]  ?
> > kthread_create_worker_on_cpu+0x70/0x70
> >         [19647.704119][ T3721]  ret_from_fork+0x22/0x30
> >         [19647.704679][ T3721] task:crawl_257_291   state:D stack:
> > 0 pid: 6494 ppid:  6435 flags:0x00000000
> >         [19647.705797][ T3721] Call Trace:
> >         [19647.706188][ T3721]  __schedule+0x388/0xaf0
> >         [19647.706723][ T3721]  ?
> > rwsem_down_write_slowpath+0x35f/0x770
> >         [19647.707414][ T3721]  schedule+0x68/0xe0
> >         [19647.707905][ T3721]  rwsem_down_write_slowpath+0x39f/0x770
> >         [19647.708597][ T3721]  down_write_nested+0xc1/0x130
> >         [19647.709167][ T3721]  lock_two_nondirectories+0x59/0x70
> >         [19647.709831][ T3721]  btrfs_remap_file_range+0x54/0x3c0
> >         [19647.710505][ T3721]  vfs_dedupe_file_range_one+0x117/0x180
> >         [19647.711197][ T3721]  vfs_dedupe_file_range+0x159/0x1e0
> >         [19647.711902][ T3721]  do_vfs_ioctl+0x551/0x720
> >         [19647.712434][ T3721]  ? __fget_files+0x109/0x1d0
> >         [19647.713010][ T3721]  __x64_sys_ioctl+0x6f/0xc0
> >         [19647.713544][ T3721]  do_syscall_64+0x38/0x90
> >         [19647.714098][ T3721]
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >         [19647.714818][ T3721] RIP: 0033:0x7f0ab2429cc7
> >         [19647.715327][ T3721] RSP: 002b:00007f0ab03241d8 EFLAGS:
> > 00000246 ORIG_RAX: 0000000000000010
> >         [19647.716326][ T3721] RAX: ffffffffffffffda RBX:
> > 00007f0ab0324420 RCX: 00007f0ab2429cc7
> >         [19647.717264][ T3721] RDX: 00007f0a981afe50 RSI:
> > 00000000c0189436 RDI: 0000000000000012
> >         [19647.718203][ T3721] RBP: 00007f0a981afe50 R08:
> > 00007f0a983759e0 R09: 0000000000000000
> >         [19647.719151][ T3721] R10: 00007ffc0f9f2080 R11:
> > 0000000000000246 R12: 00007f0a981afe50
> >         [19647.720087][ T3721] R13: 00007f0ab0324428 R14:
> > 0000000000000000 R15: 00007f0ab0324448
> >         [19647.721041][ T3721] task:crawl_256_295   state:D stack:
> > 0 pid: 6496 ppid:  6435 flags:0x00000000
> >         [19647.722126][ T3721] Call Trace:
> >         [19647.722517][ T3721]  __schedule+0x388/0xaf0
> >         [19647.723060][ T3721]  schedule+0x68/0xe0
> >         [19647.723524][ T3721]  wait_current_trans+0xed/0x150
> >         [19647.724117][ T3721]  ? do_wait_intr_irq+0xd0/0xd0
> >         [19647.724697][ T3721]  start_transaction+0x37e/0x6f0
> >         [19647.725273][ T3721]  ?
> > btrfs_inode_flags_to_xflags+0x50/0x50
> >         [19647.725969][ T3721]  btrfs_attach_transaction+0x1d/0x20
> >         [19647.726625][ T3721]  iterate_extent_inodes+0x7b/0x270
> >         [19647.727236][ T3721]  iterate_inodes_from_logical+0x9f/0xe0
> >         [19647.727912][ T3721]  ?
> > btrfs_inode_flags_to_xflags+0x50/0x50
> >         [19647.728599][ T3721]
> > btrfs_ioctl_logical_to_ino+0x183/0x210
> >         [19647.729263][ T3721]  btrfs_ioctl+0xa83/0x2fe0
> >         [19647.729818][ T3721]  ? kvm_sched_clock_read+0x18/0x30
> >         [19647.730430][ T3721]  ? sched_clock+0x9/0x10
> >         [19647.730976][ T3721]  ? __fget_files+0xe6/0x1d0
> >         [19647.731521][ T3721]  ? __fget_files+0x109/0x1d0
> >         [19647.732096][ T3721]  __x64_sys_ioctl+0x91/0xc0
> >         [19647.732647][ T3721]  ? __x64_sys_ioctl+0x91/0xc0
> >         [19647.733209][ T3721]  do_syscall_64+0x38/0x90
> >         [19647.733750][ T3721]
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >         [19647.734438][ T3721] RIP: 0033:0x7f0ab2429cc7
> >         [19647.734992][ T3721] RSP: 002b:00007f0aaf322378 EFLAGS:
> > 00000246 ORIG_RAX: 0000000000000010
> >         [19647.735994][ T3721] RAX: ffffffffffffffda RBX:
> > 0000558110d25dd0 RCX: 00007f0ab2429cc7
> >         [19647.736949][ T3721] RDX: 00007f0aaf322608 RSI:
> > 00000000c038943b RDI: 0000000000000003
> >         [19647.737895][ T3721] RBP: 00007f0aaf322550 R08:
> > 0000000000000000 R09: 00007f0aaf3227e0
> >         [19647.738862][ T3721] R10: 000019f231c642a4 R11:
> > 0000000000000246 R12: 00007f0aaf322600
> >         [19647.739799][ T3721] R13: 0000000000000003 R14:
> > 00007f0aaf322608 R15: 00007f0aaf3225e0
> >         [19647.740748][ T3721] task:crawl_257_292   state:D stack:
> > 0 pid: 6502 ppid:  6435 flags:0x00000000
> >         [19647.741832][ T3721] Call Trace:
> >         [19647.742216][ T3721]  __schedule+0x388/0xaf0
> >         [19647.742761][ T3721]  schedule+0x68/0xe0
> >         [19647.743225][ T3721]  wait_current_trans+0xed/0x150
> >         [19647.743825][ T3721]  ? do_wait_intr_irq+0xd0/0xd0
> >         [19647.744399][ T3721]  start_transaction+0x587/0x6f0
> >         [19647.745003][ T3721]  btrfs_start_transaction+0x1e/0x20
> >         [19647.745638][ T3721]
> > btrfs_replace_file_extents+0x135/0x8d0
> >         [19647.746305][ T3721]  ? release_extent_buffer+0xae/0xf0
> >         [19647.746973][ T3721]  btrfs_clone+0x828/0x8c0
> >         [19647.747513][ T3721]  btrfs_extent_same_range+0x75/0xa0
> >         [19647.748152][ T3721]  btrfs_remap_file_range+0x354/0x3c0
> >         [19647.748802][ T3721]  vfs_dedupe_file_range_one+0x117/0x180
> >         [19647.749460][ T3721]  vfs_dedupe_file_range+0x159/0x1e0
> >         [19647.750098][ T3721]  do_vfs_ioctl+0x551/0x720
> >         [19647.750666][ T3721]  ? __fget_files+0x109/0x1d0
> >         [19647.751216][ T3721]  __x64_sys_ioctl+0x6f/0xc0
> >         [19647.751777][ T3721]  do_syscall_64+0x38/0x90
> >         [19647.752290][ T3721]
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >         [19647.752992][ T3721] RIP: 0033:0x7f0ab2429cc7
> >         [19647.753511][ T3721] RSP: 002b:00007f0aac31c1d8 EFLAGS:
> > 00000246 ORIG_RAX: 0000000000000010
> >         [19647.754500][ T3721] RAX: ffffffffffffffda RBX:
> > 00007f0aac31c420 RCX: 00007f0ab2429cc7
> >         [19647.755460][ T3721] RDX: 00007f0a787fc690 RSI:
> > 00000000c0189436 RDI: 0000000000000012
> >         [19647.756406][ T3721] RBP: 00007f0a787fc690 R08:
> > 00007f0a78f4fd40 R09: 0000000000000000
> >         [19647.757340][ T3721] R10: 00007ffc0f9f2080 R11:
> > 0000000000000246 R12: 00007f0a787fc690
> >         [19647.758291][ T3721] R13: 00007f0aac31c428 R14:
> > 0000000000000000 R15: 00007f0aac31c448
> >         [19647.759261][ T3721] task:crawl_257_293   state:D stack:
> > 0 pid: 6503 ppid:  6435 flags:0x00000000
> >         [19647.760362][ T3721] Call Trace:
> >         [19647.760761][ T3721]  __schedule+0x388/0xaf0
> >         [19647.761261][ T3721]  ?
> > rwsem_down_write_slowpath+0x35f/0x770
> >         [19647.761958][ T3721]  schedule+0x68/0xe0
> >         [19647.762425][ T3721]  rwsem_down_write_slowpath+0x39f/0x770
> >         [19647.763126][ T3721]  down_write+0xbd/0x120
> >         [19647.763643][ T3721]  btrfs_remap_file_range+0x2eb/0x3c0
> >         [19647.764278][ T3721]  vfs_dedupe_file_range_one+0x117/0x180
> >         [19647.764954][ T3721]  vfs_dedupe_file_range+0x159/0x1e0
> >         [19647.765589][ T3721]  do_vfs_ioctl+0x551/0x720
> >         [19647.766115][ T3721]  ? __fget_files+0x109/0x1d0
> >         [19647.766700][ T3721]  __x64_sys_ioctl+0x6f/0xc0
> >         [19647.767238][ T3721]  do_syscall_64+0x38/0x90
> >         [19647.767772][ T3721]
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >         [19647.768458][ T3721] RIP: 0033:0x7f0ab2429cc7
> >         [19647.768990][ T3721] RSP: 002b:00007f0aabb1b1d8 EFLAGS:
> > 00000246 ORIG_RAX: 0000000000000010
> >         [19647.769986][ T3721] RAX: ffffffffffffffda RBX:
> > 00007f0aabb1b420 RCX: 00007f0ab2429cc7
> >         [19647.770951][ T3721] RDX: 00007f0a6c1f5ac0 RSI:
> > 00000000c0189436 RDI: 0000000000000012
> >         [19647.771894][ T3721] RBP: 00007f0a6c1f5ac0 R08:
> > 00007f0a6d00da10 R09: 0000000000000000
> >         [19647.772839][ T3721] R10: 00007ffc0f9f2080 R11:
> > 0000000000000246 R12: 00007f0a6c1f5ac0
> >         [19647.773789][ T3721] R13: 00007f0aabb1b428 R14:
> > 0000000000000000 R15: 00007f0aabb1b448
> >         [19647.774784][ T3721] task:crawl_256_289   state:D stack:
> > 0 pid: 6504 ppid:  6435 flags:0x00000000
> >         [19647.775882][ T3721] Call Trace:
> >         [19647.776271][ T3721]  __schedule+0x388/0xaf0
> >         [19647.776807][ T3721]  ?
> > rwsem_down_write_slowpath+0x35f/0x770
> >         [19647.777499][ T3721]  schedule+0x68/0xe0
> >         [19647.777994][ T3721]  rwsem_down_write_slowpath+0x39f/0x770
> >         [19647.778712][ T3721]  down_write_nested+0xc1/0x130
> >         [19647.779285][ T3721]  lock_two_nondirectories+0x59/0x70
> >         [19647.779931][ T3721]  btrfs_remap_file_range+0x54/0x3c0
> >         [19647.780564][ T3721]  vfs_dedupe_file_range_one+0x117/0x180
> >         [19647.781366][ T3721]  vfs_dedupe_file_range+0x159/0x1e0
> >         [19647.782009][ T3721]  do_vfs_ioctl+0x551/0x720
> >         [19647.782554][ T3721]  ? __fget_files+0x109/0x1d0
> >         [19647.783230][ T3721]  __x64_sys_ioctl+0x6f/0xc0
> >         [19647.783804][ T3721]  do_syscall_64+0x38/0x90
> >         [19647.784319][ T3721]
> > entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >         [19647.785031][ T3721] RIP: 0033:0x7f0ab2429cc7
> >         [19647.785548][ T3721] RSP: 002b:00007f0aab31a1d8 EFLAGS:
> > 00000246 ORIG_RAX: 0000000000000010
> >         [19647.786660][ T3721] RAX: ffffffffffffffda RBX:
> > 00007f0aab31a420 RCX: 00007f0ab2429cc7
> >         [19647.787609][ T3721] RDX: 00007f0a70008f00 RSI:
> > 00000000c0189436 RDI: 0000000000000012
> >         [19647.788551][ T3721] RBP: 00007f0a70008f00 R08:
> > 00007f0a708e66e0 R09: 0000000000000000
> >         [19647.789533][ T3721] R10: 00007ffc0f9f2080 R11:
> > 0000000000000246 R12: 00007f0a70008f00
> >         [19647.790482][ T3721] R13: 00007f0aab31a428 R14:
> > 0000000000000000 R15: 00007f0aab31a448
> >         [32609.668575][ T3721] sysrq: Show Locks Held
> >         [32609.673950][ T3721]
> >         [32609.673950][ T3721] Showing all locks held in the system:
> >         [32609.675276][ T3721] 1 lock held by in:imklog/3603:
> >         [32609.675885][ T3721] 1 lock held by dmesg/3720:
> >         [32609.676432][ T3721]  #0: ffff8a1406ac80e0 (&user-
> > >lock){+.+.}-{3:3}, at: devkmsg_read+0x4d/0x320
> >         [32609.678403][ T3721] 3 locks held by bash/3721:
> >         [32609.678972][ T3721]  #0: ffff8a142a589498
> > (sb_writers#4){.+.+}-{0:0}, at: ksys_write+0x70/0xf0
> >         [32609.680364][ T3721]  #1: ffffffff98f199a0
> > (rcu_read_lock){....}-{1:2}, at: __handle_sysrq+0x5/0xa0
> >         [32609.682046][ T3721]  #2: ffffffff98f199a0
> > (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x23/0x187
> >         [32609.683847][ T3721] 1 lock held by btrfs-transacti/6161:
> >         [32609.684498][ T3721]  #0: ffff8a14e0178850 (&fs_info-
> > >transaction_kthread_mutex){+.+.}-{3:3}, at:
> > transaction_kthread+0x5a/0x1b0
> >         [32609.686275][ T3721] 3 locks held by crawl_257_265/6491:
> >         [32609.686937][ T3721] 3 locks held by crawl_257_291/6494:
> >         [32609.687578][ T3721]  #0: ffff8a14bd092498
> > (sb_writers#12){.+.+}-{0:0}, at: vfs_dedupe_file_range_one+0x3b/0x180
> >         [32609.689126][ T3721]  #1: ffff8a1410d7c848 (&sb->s_type-
> > >i_mutex_key#17){+.+.}-{3:3}, at: lock_two_nondirectories+0x6b/0x70
> >         [32609.690694][ T3721]  #2: ffff8a14161a39c8 (&sb->s_type-
> > >i_mutex_key#17/4){+.+.}-{3:3}, at: lock_two_nondirectories+0x59/0x70
> >         [32609.692091][ T3721] 4 locks held by crawl_257_292/6502:
> >         [32609.692763][ T3721]  #0: ffff8a14bd092498
> > (sb_writers#12){.+.+}-{0:0}, at: vfs_dedupe_file_range_one+0x3b/0x180
> >         [32609.694014][ T3721]  #1: ffff8a131637a908 (&sb->s_type-
> > >i_mutex_key#17){+.+.}-{3:3}, at: lock_two_nondirectories+0x6b/0x70
> >         [32609.695377][ T3721]  #2: ffff8a14161a39c8 (&sb->s_type-
> > >i_mutex_key#17/4){+.+.}-{3:3}, at: lock_two_nondirectories+0x59/0x70
> >         [32609.696764][ T3721]  #3: ffff8a14bd0926b8
> > (sb_internal#2){.+.+}-{0:0}, at: btrfs_start_transaction+0x1e/0x20
> >         [32609.697986][ T3721] 2 locks held by crawl_257_293/6503:
> >         [32609.698629][ T3721]  #0: ffff8a14bd092498
> > (sb_writers#12){.+.+}-{0:0}, at: vfs_dedupe_file_range_one+0x3b/0x180
> >         [32609.699882][ T3721]  #1: ffff8a14161a39c8 (&sb->s_type-
> > >i_mutex_key#17){+.+.}-{3:3}, at: btrfs_remap_file_range+0x2eb/0x3c0
> >         [32609.701674][ T3721] 3 locks held by crawl_256_289/6504:
> >         [32609.702443][ T3721]  #0: ffff8a14bd092498
> > (sb_writers#12){.+.+}-{0:0}, at: vfs_dedupe_file_range_one+0x3b/0x180
> >         [32609.703927][ T3721]  #1: ffff8a140f2c4748 (&sb->s_type-
> > >i_mutex_key#17){+.+.}-{3:3}, at: lock_two_nondirectories+0x6b/0x70
> >         [32609.705444][ T3721]  #2: ffff8a14161a39c8 (&sb->s_type-
> > >i_mutex_key#17/4){+.+.}-{3:3}, at: lock_two_nondirectories+0x59/0x70
> >         [32609.706899][ T3721]
> >         [32609.707177][ T3721]
> > =============================================
> >
> > There is also a severe performance regression (50% slower) in btrfs
> > dedupe
> > starting in 5.11, but reverting this commit doesn't make the
> > performance
> > regression go away.  I'll follow up on that separately.