Hi,
left my box unattended for a while and lockdep reported this:
| ======================================================
| WARNING: possible circular locking dependency detected
| 5.16.0-rc1+ #12 Not tainted
| ------------------------------------------------------
| kswapd1/510 is trying to acquire lock:
| ffff88800c98ac70 (&xfs_nondir_ilock_class){++++}-{3:3}, at: xfs_icwalk_ag+0x365/0x810
|
| but task is already holding lock:
| ffffffff82a76d60 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x4c4/0x5b0
|
| which lock already depends on the new lock.
|
|
| the existing dependency chain (in reverse order) is:
|
| -> #1 (fs_reclaim){+.+.}-{0:0}:
| fs_reclaim_acquire+0xa1/0xd0
| __alloc_pages+0xed/0x380
| new_slab+0x277/0x430
| ___slab_alloc.constprop.0+0xb6a/0xfc0
| __slab_alloc.constprop.0+0x42/0x80
| __kmalloc_node+0xcc/0x200
| xfs_attr_copy_value+0x6e/0x90
| xfs_attr_get+0xa0/0xc0
| xfs_get_acl+0xe4/0x210
| get_acl.part.0+0x55/0x110
| posix_acl_xattr_get+0x6a/0x120
| vfs_getxattr+0x172/0x1a0
| getxattr+0xb5/0x240
| __x64_sys_fgetxattr+0x66/0xb0
| do_syscall_64+0x59/0x80
| entry_SYSCALL_64_after_hwframe+0x44/0xae
|
| -> #0 (&xfs_nondir_ilock_class){++++}-{3:3}:
| __lock_acquire+0x12cb/0x2320
| lock_acquire+0xc9/0x2e0
| down_write_nested+0x42/0x110
| xfs_icwalk_ag+0x365/0x810
| xfs_icwalk+0x38/0xa0
| xfs_reclaim_inodes_nr+0x90/0xc0
| super_cache_scan+0x18e/0x1f0
| shrink_slab.constprop.0+0x1cf/0x4d0
| shrink_node+0x1e2/0x470
| balance_pgdat+0x26d/0x5b0
| kswapd+0x224/0x4e0
| kthread+0x17a/0x1a0
| ret_from_fork+0x1f/0x30
|
| other info that might help us debug this:
|
| Possible unsafe locking scenario:
| CPU0 CPU1
| ---- ----
| lock(fs_reclaim);
| lock(&xfs_nondir_ilock_class);
| lock(fs_reclaim);
| lock(&xfs_nondir_ilock_class);
|
| *** DEADLOCK ***
|
| 3 locks held by kswapd1/510:
| #0: ffffffff82a76d60 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x4c4/0x5b0
| #1: ffffffff82a69d58 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab.constprop.0+0x3b/0x4d0
| #2: ffff888553ccd0e8 (&type->s_umount_key#32){++++}-{3:3}, at: super_cache_scan+0x38/0x1f0
|
| stack backtrace:
| CPU: 12 PID: 510 Comm: kswapd1 Not tainted 5.16.0-rc1+ #12
| Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.03.0003.041920141333 04/19/2014
| Call Trace:
| <TASK>
| dump_stack_lvl+0x45/0x59
| check_noncircular+0xff/0x110
| __lock_acquire+0x12cb/0x2320
| lock_acquire+0xc9/0x2e0
| ? xfs_icwalk_ag+0x365/0x810
| ? lock_is_held_type+0xd6/0x130
| down_write_nested+0x42/0x110
| ? xfs_icwalk_ag+0x365/0x810
| xfs_icwalk_ag+0x365/0x810
| xfs_icwalk+0x38/0xa0
| xfs_reclaim_inodes_nr+0x90/0xc0
| super_cache_scan+0x18e/0x1f0
| shrink_slab.constprop.0+0x1cf/0x4d0
| shrink_node+0x1e2/0x470
| balance_pgdat+0x26d/0x5b0
| ? lock_is_held_type+0xd6/0x130
| kswapd+0x224/0x4e0
| ? wait_woken+0x90/0x90
| ? balance_pgdat+0x5b0/0x5b0
| kthread+0x17a/0x1a0
| ? set_kthread_struct+0x40/0x40
| ret_from_fork+0x1f/0x30
| </TASK>
It appears to be related to commit
d634525db63e9 ("xfs: replace kmem_alloc_large() with kvmalloc()")
as SLUB's new_slab() has
| return allocate_slab(s,
| flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
which drops the __GFP_NOLOCKDEP as used in xfs_attr_copy_value():
| args->value = kvmalloc(valuelen, GFP_KERNEL | __GFP_NOLOCKDEP);
However I can't tell if this should happen or not I'm just pointing out
that it is.
Sebastian
