1. 06 Mar, 2023 2 commits
    • Qu Wenruo's avatar
      btrfs: ioctl: return device fsid from DEV_INFO ioctl · 2943868a
      Qu Wenruo authored
      Currently user space utilizes dev info ioctl to grab the info of a
      certain devid, this includes its device uuid.  But the returned info is
      not enough to determine if a device is a seed.
      
      Commit a26d60de ("btrfs: sysfs: add devinfo/fsid to retrieve actual
      fsid from the device") exports the same value in sysfs so this is for
      parity with ioctl.  Add a new member, fsid, into
      btrfs_ioctl_dev_info_args, and populate the member with fsid value.
      
      This should not cause any compatibility problem, following the
      combinations:
      
      - Old user space, old kernel
      - Old user space, new kernel
        User space tool won't even check the new member.
      
      - New user space, old kernel
        The kernel won't touch the new member, and user space tool should
        zero out its argument, thus the new member is all zero.
      
        User space tool can then know the kernel doesn't support this fsid
        reporting, and falls back to whatever they can.
      
      - New user space, new kernel
        Go as planned.
      
        Would find the fsid member is no longer zero, and trust its value.
      Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
      Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
      Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      2943868a
    • Boris Burkov's avatar
      btrfs: fix potential dead lock in size class loading logic · 12148367
      Boris Burkov authored
      As reported by Filipe, there's a potential deadlock caused by
      using btrfs_search_forward on commit_root. The locking there is
      unconditional, even if ->skip_locking and ->search_commit_root is set.
      It's not meant to be used for commit roots, so it always needs to do
      locking.
      
      So if another task is COWing a child node of the same root node and
      then needs to wait for block group caching to complete when trying to
      allocate a metadata extent, it deadlocks.
      
      For example:
      
      [539604.239315] sysrq: Show Blocked State
      [539604.240133] task:kworker/u16:6   state:D stack:0     pid:2119594 ppid:2      flags:0x00004000
      [539604.241613] Workqueue: btrfs-cache btrfs_work_helper [btrfs]
      [539604.242673] Call Trace:
      [539604.243129]  <TASK>
      [539604.243925]  __schedule+0x41d/0xee0
      [539604.244797]  ? rcu_read_lock_sched_held+0x12/0x70
      [539604.245399]  ? rwsem_down_read_slowpath+0x185/0x490
      [539604.246111]  schedule+0x5d/0xf0
      [539604.246593]  rwsem_down_read_slowpath+0x2da/0x490
      [539604.247290]  ? rcu_barrier_tasks_trace+0x10/0x20
      [539604.248090]  __down_read_common+0x3d/0x150
      [539604.248702]  down_read_nested+0xc3/0x140
      [539604.249280]  __btrfs_tree_read_lock+0x24/0x100 [btrfs]
      [539604.250097]  btrfs_read_lock_root_node+0x48/0x60 [btrfs]
      [539604.250915]  btrfs_search_forward+0x59/0x460 [btrfs]
      [539604.251781]  ? btrfs_global_root+0x50/0x70 [btrfs]
      [539604.252476]  caching_thread+0x1be/0x920 [btrfs]
      [539604.253167]  btrfs_work_helper+0xf6/0x400 [btrfs]
      [539604.253848]  process_one_work+0x24f/0x5a0
      [539604.254476]  worker_thread+0x52/0x3b0
      [539604.255166]  ? __pfx_worker_thread+0x10/0x10
      [539604.256047]  kthread+0xf0/0x120
      [539604.256591]  ? __pfx_kthread+0x10/0x10
      [539604.257212]  ret_from_fork+0x29/0x50
      [539604.257822]  </TASK>
      [539604.258233] task:btrfs-transacti state:D stack:0     pid:2236474 ppid:2      flags:0x00004000
      [539604.259802] Call Trace:
      [539604.260243]  <TASK>
      [539604.260615]  __schedule+0x41d/0xee0
      [539604.261205]  ? rcu_read_lock_sched_held+0x12/0x70
      [539604.262000]  ? rwsem_down_read_slowpath+0x185/0x490
      [539604.262822]  schedule+0x5d/0xf0
      [539604.263374]  rwsem_down_read_slowpath+0x2da/0x490
      [539604.266228]  ? lock_acquire+0x160/0x310
      [539604.266917]  ? rcu_read_lock_sched_held+0x12/0x70
      [539604.267996]  ? lock_contended+0x19e/0x500
      [539604.268720]  __down_read_common+0x3d/0x150
      [539604.269400]  down_read_nested+0xc3/0x140
      [539604.270057]  __btrfs_tree_read_lock+0x24/0x100 [btrfs]
      [539604.271129]  btrfs_read_lock_root_node+0x48/0x60 [btrfs]
      [539604.272372]  btrfs_search_slot+0x143/0xf70 [btrfs]
      [539604.273295]  update_block_group_item+0x9e/0x190 [btrfs]
      [539604.274282]  btrfs_start_dirty_block_groups+0x1c4/0x4f0 [btrfs]
      [539604.275381]  ? __mutex_unlock_slowpath+0x45/0x280
      [539604.276390]  btrfs_commit_transaction+0xee/0xed0 [btrfs]
      [539604.277391]  ? lock_acquire+0x1a4/0x310
      [539604.278080]  ? start_transaction+0xcb/0x6c0 [btrfs]
      [539604.279099]  transaction_kthread+0x142/0x1c0 [btrfs]
      [539604.279996]  ? __pfx_transaction_kthread+0x10/0x10 [btrfs]
      [539604.280673]  kthread+0xf0/0x120
      [539604.281050]  ? __pfx_kthread+0x10/0x10
      [539604.281496]  ret_from_fork+0x29/0x50
      [539604.281966]  </TASK>
      [539604.282255] task:fsstress        state:D stack:0     pid:2236483 ppid:1      flags:0x00004006
      [539604.283897] Call Trace:
      [539604.284700]  <TASK>
      [539604.285088]  __schedule+0x41d/0xee0
      [539604.285660]  schedule+0x5d/0xf0
      [539604.286175]  btrfs_wait_block_group_cache_progress+0xf2/0x170 [btrfs]
      [539604.287342]  ? __pfx_autoremove_wake_function+0x10/0x10
      [539604.288450]  find_free_extent+0xd93/0x1750 [btrfs]
      [539604.289256]  ? _raw_spin_unlock+0x29/0x50
      [539604.289911]  ? btrfs_get_alloc_profile+0x127/0x2a0 [btrfs]
      [539604.290843]  btrfs_reserve_extent+0x147/0x290 [btrfs]
      [539604.291943]  btrfs_alloc_tree_block+0xcb/0x3e0 [btrfs]
      [539604.292903]  __btrfs_cow_block+0x138/0x580 [btrfs]
      [539604.293773]  btrfs_cow_block+0x10e/0x240 [btrfs]
      [539604.294595]  btrfs_search_slot+0x7f3/0xf70 [btrfs]
      [539604.295585]  btrfs_update_device+0x71/0x1b0 [btrfs]
      [539604.296459]  btrfs_chunk_alloc_add_chunk_item+0xe0/0x340 [btrfs]
      [539604.297489]  btrfs_chunk_alloc+0x1bf/0x490 [btrfs]
      [539604.298335]  find_free_extent+0x6fa/0x1750 [btrfs]
      [539604.299174]  ? _raw_spin_unlock+0x29/0x50
      [539604.299950]  ? btrfs_get_alloc_profile+0x127/0x2a0 [btrfs]
      [539604.300918]  btrfs_reserve_extent+0x147/0x290 [btrfs]
      [539604.301797]  btrfs_alloc_tree_block+0xcb/0x3e0 [btrfs]
      [539604.303017]  ? lock_release+0x224/0x4a0
      [539604.303855]  __btrfs_cow_block+0x138/0x580 [btrfs]
      [539604.304789]  btrfs_cow_block+0x10e/0x240 [btrfs]
      [539604.305611]  btrfs_search_slot+0x7f3/0xf70 [btrfs]
      [539604.306682]  ? btrfs_global_root+0x50/0x70 [btrfs]
      [539604.308198]  lookup_inline_extent_backref+0x17b/0x7a0 [btrfs]
      [539604.309254]  lookup_extent_backref+0x43/0xd0 [btrfs]
      [539604.310122]  __btrfs_free_extent+0xf8/0x810 [btrfs]
      [539604.310874]  ? lock_release+0x224/0x4a0
      [539604.311724]  ? btrfs_merge_delayed_refs+0x17b/0x1d0 [btrfs]
      [539604.313023]  __btrfs_run_delayed_refs+0x2ba/0x1260 [btrfs]
      [539604.314271]  btrfs_run_delayed_refs+0x8f/0x1c0 [btrfs]
      [539604.315445]  ? rcu_read_lock_sched_held+0x12/0x70
      [539604.316706]  btrfs_commit_transaction+0xa2/0xed0 [btrfs]
      [539604.317855]  ? do_raw_spin_unlock+0x4b/0xa0
      [539604.318544]  ? _raw_spin_unlock+0x29/0x50
      [539604.319240]  create_subvol+0x53d/0x6e0 [btrfs]
      [539604.320283]  btrfs_mksubvol+0x4f5/0x590 [btrfs]
      [539604.321220]  __btrfs_ioctl_snap_create+0x11b/0x180 [btrfs]
      [539604.322307]  btrfs_ioctl_snap_create_v2+0xc6/0x150 [btrfs]
      [539604.323295]  btrfs_ioctl+0x9f7/0x33e0 [btrfs]
      [539604.324331]  ? rcu_read_lock_sched_held+0x12/0x70
      [539604.325137]  ? lock_release+0x224/0x4a0
      [539604.325808]  ? __x64_sys_ioctl+0x87/0xc0
      [539604.326467]  __x64_sys_ioctl+0x87/0xc0
      [539604.327109]  do_syscall_64+0x38/0x90
      [539604.327875]  entry_SYSCALL_64_after_hwframe+0x72/0xdc
      [539604.328792] RIP: 0033:0x7f05a7babaeb
      
      This needs to use regular btrfs_search_slot() with some skip and stop
      logic.
      
      Since we only consider five samples (five search slots), don't bother
      with the complexity of looking for commit_root_sem contention. If
      necessary, it can be added to the load function in between samples.
      Reported-by: default avatarFilipe Manana <fdmanana@kernel.org>
      Link: https://lore.kernel.org/linux-btrfs/CAL3q7H7eKMD44Z1+=Kb-1RFMMeZpAm2fwyO59yeBwCcSOU80Pg@mail.gmail.com/
      Fixes: c7eec3d9 ("btrfs: load block group size class when caching")
      Signed-off-by: default avatarBoris Burkov <boris@bur.io>
      Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
      12148367
  2. 01 Mar, 2023 1 commit
  3. 15 Feb, 2023 37 commits