Re: [PATCH v2 04/18] nfs: separate locked regions in nfs_clear_verifier_directory()

[Chuck Lever]

On Sat, Aug 15, 2026, at 2:21 PM, NeilBrown wrote:
> nfs_clear_verifier_directory() locks the dir to call
>   nfs_unset_verifier_delegated()
> and also to walk the d_children list.
> These are two separate needs and they don't need to both
> be in the same locked region.
>
> Subsequent patches will use a helper for walking the d_children list and
> that helper may drop the lock temporarily.  To simplify this transition,
> split the locked range by dropping and retaking the lock between to make
> two separate locked regions.

I hit this running xfstests against tmpfs with the series applied.  The
trigger was incidental (an unrelated process chmod'ed a file on an
NFSv4 mount while xfstests was running) so it is not deterministic, but
the path looks reachable by any SETATTR that returns a delegation on a
directory:

  BUG: sleeping function called from invalid context at fs/nfs/dir.c:1497
  in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2385380
  preempt_count: 1, expected: 0
  Call Trace:
   __might_resched+0x165/0x180
   nfs_clear_verifier_delegated+0x112/0x250 [nfs]
   nfs_start_delegation_return+0xa1/0x130 [nfsv4]
   nfs4_inode_return_delegation+0x1b/0xf0 [nfsv4]
   nfs4_inode_make_writeable+0xa9/0x130 [nfsv4]
   nfs4_proc_setattr+0xa2/0xf0 [nfsv4]
   nfs_setattr+0x1f2/0x480 [nfs]
   notify_change+0x321/0x380
   chmod_common+0x10d/0x1c0
   do_fchmodat+0x8a/0x110
   __x64_sys_chmod+0x1d/0x30

Line 1497 is the d_for_each_positive_child() call.


-- 
Chuck Lever