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We are currently getting this lockdep splat in btrfs/161: ====================================================== WARNING: possible circular locking dependency detected 5.8.0-rc5+ #20 Tainted: G E ------------------------------------------------------ mount/678048 is trying to acquire lock: ffff9b769f15b6e0 (&fs_devs->device_list_mutex){+.+.}-{3:3}, at: clone_fs_devices+0x4d/0x170 [btrfs] but task is already holding lock: ffff9b76abdb08d0 (&fs_info->chunk_mutex){+.+.}-{3:3}, at: btrfs_read_chunk_tree+0x6a/0x800 [btrfs] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&fs_info->chunk_mutex){+.+.}-{3:3}: __mutex_lock+0x8b/0x8f0 btrfs_init_new_device+0x2d2/0x1240 [btrfs] btrfs_ioctl+0x1de/0x2d20 [btrfs] ksys_ioctl+0x87/0xc0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x52/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&fs_devs->device_list_mutex){+.+.}-{3:3}: __lock_acquire+0x1240/0x2460 lock_acquire+0xab/0x360 __mutex_lock+0x8b/0x8f0 clone_fs_devices+0x4d/0x170 [btrfs] btrfs_read_chunk_tree+0x330/0x800 [btrfs] open_ctree+0xb7c/0x18ce [btrfs] btrfs_mount_root.cold+0x13/0xfa [btrfs] legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 fc_mount+0xe/0x40 vfs_kern_mount.part.0+0x71/0x90 btrfs_mount+0x13b/0x3e0 [btrfs] legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 do_mount+0x7de/0xb30 __x64_sys_mount+0x8e/0xd0 do_syscall_64+0x52/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->chunk_mutex); lock(&fs_devs->device_list_mutex); lock(&fs_info->chunk_mutex); lock(&fs_devs->device_list_mutex); *** DEADLOCK *** 3 locks held by mount/678048: #0: ffff9b75ff5fb0e0 (&type->s_umount_key#63/1){+.+.}-{3:3}, at: alloc_super+0xb5/0x380 #1: ffffffffc0c2fbc8 (uuid_mutex){+.+.}-{3:3}, at: btrfs_read_chunk_tree+0x54/0x800 [btrfs] #2: ffff9b76abdb08d0 (&fs_info->chunk_mutex){+.+.}-{3:3}, at: btrfs_read_chunk_tree+0x6a/0x800 [btrfs] stack backtrace: CPU: 2 PID: 678048 Comm: mount Tainted: G E 5.8.0-rc5+ #20 Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./890FX Deluxe5, BIOS P1.40 05/03/2011 Call Trace: dump_stack+0x96/0xd0 check_noncircular+0x162/0x180 __lock_acquire+0x1240/0x2460 ? asm_sysvec_apic_timer_interrupt+0x12/0x20 lock_acquire+0xab/0x360 ? clone_fs_devices+0x4d/0x170 [btrfs] __mutex_lock+0x8b/0x8f0 ? clone_fs_devices+0x4d/0x170 [btrfs] ? rcu_read_lock_sched_held+0x52/0x60 ? cpumask_next+0x16/0x20 ? module_assert_mutex_or_preempt+0x14/0x40 ? __module_address+0x28/0xf0 ? clone_fs_devices+0x4d/0x170 [btrfs] ? static_obj+0x4f/0x60 ? lockdep_init_map_waits+0x43/0x200 ? clone_fs_devices+0x4d/0x170 [btrfs] clone_fs_devices+0x4d/0x170 [btrfs] btrfs_read_chunk_tree+0x330/0x800 [btrfs] open_ctree+0xb7c/0x18ce [btrfs] ? super_setup_bdi_name+0x79/0xd0 btrfs_mount_root.cold+0x13/0xfa [btrfs] ? vfs_parse_fs_string+0x84/0xb0 ? rcu_read_lock_sched_held+0x52/0x60 ? kfree+0x2b5/0x310 legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 fc_mount+0xe/0x40 vfs_kern_mount.part.0+0x71/0x90 btrfs_mount+0x13b/0x3e0 [btrfs] ? cred_has_capability+0x7c/0x120 ? rcu_read_lock_sched_held+0x52/0x60 ? legacy_get_tree+0x30/0x50 legacy_get_tree+0x30/0x50 vfs_get_tree+0x28/0xc0 do_mount+0x7de/0xb30 ? memdup_user+0x4e/0x90 __x64_sys_mount+0x8e/0xd0 do_syscall_64+0x52/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This is because btrfs_read_chunk_tree() can come upon DEV_EXTENT's and then read the device, which takes the device_list_mutex. The device_list_mutex needs to be taken before the chunk_mutex, so this is a problem. We only really need the chunk mutex around adding the chunk, so move the mutex around read_one_chunk. An argument could be made that we don't even need the chunk_mutex here as it's during mount, and we are protected by various other locks. However we already have special rules for ->device_list_mutex, and I'd rather not have another special case for ->chunk_mutex. CC: stable@vger.kernel.org # 4.19+ Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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| .. | ||
| tests | ||
| acl.c | ||
| async-thread.c | ||
| async-thread.h | ||
| backref.c | ||
| backref.h | ||
| block-group.c | ||
| block-group.h | ||
| block-rsv.c | ||
| block-rsv.h | ||
| btrfs_inode.h | ||
| check-integrity.c | ||
| check-integrity.h | ||
| compression.c | ||
| compression.h | ||
| ctree.c | ||
| ctree.h | ||
| delalloc-space.c | ||
| delalloc-space.h | ||
| delayed-inode.c | ||
| delayed-inode.h | ||
| delayed-ref.c | ||
| delayed-ref.h | ||
| dev-replace.c | ||
| dev-replace.h | ||
| dir-item.c | ||
| discard.c | ||
| discard.h | ||
| disk-io.c | ||
| disk-io.h | ||
| export.c | ||
| export.h | ||
| extent_io.c | ||
| extent_io.h | ||
| extent_map.c | ||
| extent_map.h | ||
| extent-io-tree.h | ||
| extent-tree.c | ||
| file-item.c | ||
| file.c | ||
| free-space-cache.c | ||
| free-space-cache.h | ||
| free-space-tree.c | ||
| free-space-tree.h | ||
| inode-item.c | ||
| inode-map.c | ||
| inode-map.h | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| locking.c | ||
| locking.h | ||
| lzo.c | ||
| Makefile | ||
| misc.h | ||
| ordered-data.c | ||
| ordered-data.h | ||
| orphan.c | ||
| print-tree.c | ||
| print-tree.h | ||
| props.c | ||
| props.h | ||
| qgroup.c | ||
| qgroup.h | ||
| raid56.c | ||
| raid56.h | ||
| rcu-string.h | ||
| reada.c | ||
| ref-verify.c | ||
| ref-verify.h | ||
| reflink.c | ||
| reflink.h | ||
| relocation.c | ||
| root-tree.c | ||
| scrub.c | ||
| send.c | ||
| send.h | ||
| space-info.c | ||
| space-info.h | ||
| struct-funcs.c | ||
| super.c | ||
| sysfs.c | ||
| sysfs.h | ||
| transaction.c | ||
| transaction.h | ||
| tree-checker.c | ||
| tree-checker.h | ||
| tree-defrag.c | ||
| tree-log.c | ||
| tree-log.h | ||
| ulist.c | ||
| ulist.h | ||
| uuid-tree.c | ||
| volumes.c | ||
| volumes.h | ||
| xattr.c | ||
| xattr.h | ||
| zlib.c | ||
| zstd.c | ||