Hi I noticed that a running `btrfs scrub` operation prevents a system from suspending to RAM. I wonder whether this is a known issue and being worked on. A kernel trace leading to btrfs scrub can be found attached. My current system setup: NixOS 19.09 kernel 4.19.98 btrfs-progs v5.2.1 I can also try to reproduce this issue with a more recent kernel version. (am currently on a train with bad link) In the downstream bug report [1] suggests that this could be resolved/ worked around in systemd by adding `Conflicts=suspend.target sleep.target? to the scrubbing service's systemd unit. So should this be managed at btrfs (kernel) level or in systemd? All the best schmittlauch [1] https://github.com/NixOS/nixpkgs/issues/79086
systemd[1]: Starting Suspend... systemd-sleep[15702]: Suspending system... kernel: PM: Syncing filesystems ... done. kernel: Freezing user space processes ... kernel: Freezing of tasks failed after 20.007 seconds (1 tasks refusing to freeze, wq_busy=0): kernel: btrfs D 0 12483 1 0x00000004 kernel: Call Trace: kernel: ? __schedule+0x1f4/0x820 kernel: ? scrub_missing_raid56_end_io+0x40/0x40 [btrfs] kernel: schedule+0x28/0x80 kernel: scrub_add_page_to_rd_bio+0x211/0x2c0 [btrfs] kernel: ? wait_woken+0x80/0x80 kernel: scrub_pages+0x239/0x430 [btrfs] kernel: scrub_stripe+0x72b/0xee0 [btrfs] kernel: ? kmem_cache_alloc+0x158/0x1c0 kernel: ? btrfs_check_space_for_delayed_refs+0xc7/0x100 [btrfs] kernel: ? btrfs_block_rsv_check+0x20/0x60 [btrfs] kernel: ? scrub_chunk+0xd2/0x130 [btrfs] kernel: scrub_chunk+0xd2/0x130 [btrfs] kernel: scrub_enumerate_chunks+0x20f/0x570 [btrfs] kernel: ? wait_woken+0x60/0x80 kernel: btrfs_scrub_dev+0x1e2/0x580 [btrfs] kernel: ? __kmalloc_track_caller+0x167/0x210 kernel: btrfs_ioctl+0xfea/0x31b0 [btrfs] kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? do_vfs_ioctl+0xa4/0x620 kernel: do_vfs_ioctl+0xa4/0x620 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? get_task_io_context+0x43/0x80 kernel: ksys_ioctl+0x60/0x90 kernel: ? __switch_to+0x115/0x440 kernel: __x64_sys_ioctl+0x16/0x20 kernel: do_syscall_64+0x4e/0x100 kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 kernel: RIP: 0033:0x7f7da656cb57 kernel: Code: Bad RIP value. kernel: RSP: 002b:00007f7da647dd48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 kernel: RAX: ffffffffffffffda RBX: 0000000000b163e0 RCX: 00007f7da656cb57 kernel: RDX: 0000000000b163e0 RSI: 00000000c400941b RDI: 0000000000000003 kernel: RBP: 0000000000000000 R08: 00007f7da647e700 R09: 0000000000000000 kernel: R10: 00007f7da647e700 R11: 0000000000000246 R12: 00007ffd7f26ddce kernel: R13: 00007ffd7f26ddcf R14: 00007f7da647e700 R15: 00007f7da67c9000 kernel: OOM killer enabled. kernel: Restarting tasks ... done. kernel: PM: suspend exit kernel: PM: suspend entry (s2idle) rtkit-daemon[2121]: Demoted 5 threads. kernel: PM: Syncing filesystems ... done. kernel: Freezing user space processes ... kernel: Freezing of tasks failed after 20.001 seconds (1 tasks refusing to freeze, wq_busy=0): kernel: btrfs D 0 12483 1 0x00000004 kernel: Call Trace: kernel: ? __schedule+0x1f4/0x820 kernel: ? scrub_missing_raid56_end_io+0x40/0x40 [btrfs] kernel: schedule+0x28/0x80 kernel: scrub_add_page_to_rd_bio+0x211/0x2c0 [btrfs] kernel: ? wait_woken+0x80/0x80 kernel: scrub_pages+0x239/0x430 [btrfs] kernel: ? btrfs_lookup_csums_range+0x93/0x450 [btrfs] kernel: scrub_stripe+0x72b/0xee0 [btrfs] kernel: ? start_transaction+0xef/0x3f0 [btrfs] kernel: ? kmem_cache_alloc+0x158/0x1c0 kernel: ? btrfs_check_space_for_delayed_refs+0xc7/0x100 [btrfs] kernel: ? btrfs_block_rsv_check+0x20/0x60 [btrfs] kernel: ? scrub_chunk+0xd2/0x130 [btrfs] kernel: ? scrub_chunk+0xd2/0x130 [btrfs] kernel: ? scrub_enumerate_chunks+0x20f/0x570 [btrfs] kernel: ? wait_woken+0x60/0x80 kernel: ? btrfs_scrub_dev+0x1e2/0x580 [btrfs] kernel: ? __kmalloc_track_caller+0x167/0x210 kernel: ? btrfs_ioctl+0xfea/0x31b0 [btrfs] kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? do_vfs_ioctl+0xa4/0x620 kernel: ? do_vfs_ioctl+0xa4/0x620 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? __switch_to_asm+0x35/0x70 kernel: ? __switch_to_asm+0x41/0x70 kernel: ? get_task_io_context+0x43/0x80 kernel: ? ksys_ioctl+0x60/0x90 kernel: ? __switch_to+0x115/0x440 kernel: ? __x64_sys_ioctl+0x16/0x20 kernel: ? do_syscall_64+0x4e/0x100 kernel: ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 kernel: OOM killer enabled. kernel: Restarting tasks ... done.
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