On Fri, Jul 23, 2021 at 10:49:19AM -0700, Luis Chamberlain wrote:

We are talking about sysfs files and you're argument is that
try_module_get() should lock the module, and so cannot be used
in sysfs files. My point is that such module lock is inferred:

1) Sysfs files are created by a module, that same module is responsible
   for removing the same sysfs files.
2) The module can only be removed and gone, once *all* sysfs files are
   removed first.
3) If any of the module's sysfs files are present the module must
   still be present
4) kernfs ensures that if a file is opened the file will not be
   removed until any pending operation completes
5) If a sysfs file is used to write something, that means the
   sysfs file has not yet been removed, and we know it will
   remain in existance throughout its entire operation
6) When a sysfs file operation is being run, the module must
   always exist

Greg,

I'm inclined to believe my original generic solution would be better
again [0]. Specially since we can drop the dev_type_get() / dev_type_put()
stuff.

Thoughts?

[0] https://lore.kernel.org/linux-block/20210401235925.GR4332@42.do-not-panic.com/ (local)

  Luis