inotify: do not call into namei() with a locked vnode

[kib]

Summary

PR: 288127

[markj]

Thank you. I guess the problem arises when the directory is a mount point, and we need to upgrade the lock?

[kib]

In D51233#1169810, @markj wrote:

Thank you. I guess the problem arises when the directory is a mount point, and we need to upgrade the lock?

For zfs, most likely it was a walk over the snapshot.
But it is generic rule that namei(9) must not be called while owning any vnode lock or busy reference on a mp. For instance, another reason might be non-shared locked fs, or non-recursive vnode lock.
As I noted in my mail to the list, the patch was a guess.