Delays at startup: btree trans held srcu lock (delaying memory reclaim) for 19 seconds

[neilg]

I consistently get slow startups on one of my machines because of repeated occurrences of this problem:

[   94.017691] ------------[ cut here ]------------
[   94.017695] btree trans held srcu lock (delaying memory reclaim) for 19 seconds
[   94.017709] WARNING: CPU: 4 PID: 820 at fs/bcachefs/btree_iter.c:3028 bch2_trans_put+0x244/0x250 [bcachefs]
[   94.017756] Modules linked in: poly1305_generic libpoly1305 poly1305_x86_64 chacha_generic chacha_x86_64 libchacha bcachefs libcrc32c crc32c_generic lz4_compress lz4hc_compress xor raid6_pq sr_mod cdrom usb_storage scsi_mod scsi_common hid_generic usbhid hid xhci_pci nvme thunderbolt xhci_hcd nvme_core crc32c_intel sha256_ssse3 nvme_auth amdgpu video wmi amdxcp i2c_algo_bit drm_ttm_helper ttm drm_exec gpu_sched drm_suballoc_helper drm_buddy drm_display_helper cec crc16 dm_mod dax
[   94.017794] CPU: 4 UID: 0 PID: 820 Comm: perl Tainted: G        W          6.12.8 #1-NixOS
[   94.017797] Tainted: [W]=WARN
[   94.017798] Hardware name: Framework Laptop 16 (AMD Ryzen 7040 Series)/FRANMZCP09, BIOS 03.05 11/13/2024
[   94.017800] RIP: 0010:bch2_trans_put+0x244/0x250 [bcachefs]
[   94.017816] Code: d5 c6 48 c7 c7 18 e3 a2 c1 48 b8 cf f7 53 e3 a5 9b c4 20 48 29 ca 48 c1 ea 03 48 f7 e2 48 89 d6 48 c1 ee 04 e8 dd 02 01 c5 90 <0f> 0b 90 90 eb 9c 90 0f 0b 90 eb a8 90 90 90 90 90 90 90 90 90 90
[   94.017818] RSP: 0018:ffffab8547063a00 EFLAGS: 00010246
[   94.017820] RAX: 0000000000000000 RBX: ffff98048fddad60 RCX: 0000000000000000
[   94.017821] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[   94.017822] RBP: ffff98030ae94000 R08: 0000000000000000 R09: 0000000000000000
[   94.017823] R10: 0000000000000000 R11: 0000000000000000 R12: ffff98030ae94000
[   94.017824] R13: ffff9803112c0000 R14: ffff9803112c0000 R15: ffff98048fddad60
[   94.017825] FS:  00007f6df4fe6b80(0000) GS:ffff9811dfc00000(0000) knlGS:0000000000000000
[   94.017827] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   94.017828] CR2: 0000000011788078 CR3: 00000001b6f9e000 CR4: 0000000000f50ef0
[   94.017829] PKRU: 55555554
[   94.017830] Call Trace:
[   94.017834]  <TASK>
[   94.017836]  ? bch2_trans_put+0x244/0x250 [bcachefs]
[   94.017850]  ? __warn.cold+0x93/0xf6
[   94.017854]  ? bch2_trans_put+0x244/0x250 [bcachefs]
[   94.017869]  ? report_bug+0x10d/0x150
[   94.017872]  ? srso_alias_return_thunk+0x5/0xfbef5
[   94.017876]  ? handle_bug+0x61/0xb0
[   94.017879]  ? exc_invalid_op+0x17/0x80
[   94.017880]  ? asm_exc_invalid_op+0x1a/0x20
[   94.017885]  ? bch2_trans_put+0x244/0x250 [bcachefs]
[   94.017899]  __bch2_create+0x5c0/0x610 [bcachefs]
[   94.017930]  ? bch2_create+0x2a/0x70 [bcachefs]
[   94.017944]  bch2_create+0x2a/0x70 [bcachefs]
[   94.017958]  path_openat+0x1029/0x12f0
[   94.017964]  do_filp_open+0xc4/0x170
[   94.017969]  do_sys_openat2+0xb4/0xe0
[   94.017972]  __x64_sys_openat+0x55/0xb0
[   94.017974]  do_syscall_64+0xb7/0x210
[   94.017977]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[   94.017980] RIP: 0033:0x7f6df490ba00
[   94.017983] Code: 83 e2 40 75 65 89 f0 f7 d0 a9 00 00 41 00 74 5a 80 3d 73 26 0f 00 00 74 7e 89 da 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 a4 00 00 00 48 8b 54 24 28 64 48 2b 14 25
[   94.017984] RSP: 002b:00007ffd2b6e86c0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
[   94.017986] RAX: ffffffffffffffda RBX: 0000000000080041 RCX: 00007f6df490ba00
[   94.017987] RDX: 0000000000080041 RSI: 0000000011c8b150 RDI: 00000000ffffff9c
[   94.017988] RBP: 0000000011c8b150 R08: 00007ffd2b6e8940 R09: 00000000ffffffff
[   94.017989] R10: 00000000000001a4 R11: 0000000000000202 R12: 0000000000000000
[   94.017990] R13: 0000000011c8b150 R14: 00000000114b7cc0 R15: 0000000000000000
[   94.017993]  </TASK>
[   94.017994] ---[ end trace 0000000000000000 ]---