Re: [PATCH 03/19] fs: release anon dev_t in deactivate_locked_super

[Christoph Hellwig]

On Tue, Sep 26, 2023 at 10:25:15PM +0100, Al Viro wrote:
> Before your patch: foo_kill_super() calls kill_anon_super(),
> which calls kill_super_notify(), which removes the sucker from
> the list, then frees ->s_fs_info.  After your patch:
> removal from the lists happens via the call of kill_super_notify()
> *after* both of your methods had been called, while freeing
> ->s_fs_info happens from the method call.  IOW, you've restored
> the situation prior to "super: ensure valid info".  The whole
> point of that commit had been to make sure that we have nothing
> in the lists with ->s_fs_info pointing to a freed object.
> 
> It's not about free_anon_bdev(); that part is fine - it's the
> "we can drop the weird second call site of kill_super_notify()"
> thing that is broken.

The point has been to only release the anon dev_t after
kill_super_notify, to prevent two of them beeing reused.

Which we do as the free_anon_bdev is done directly in
deactivate_locked_super.  The new ->free_sb for non-block file systems
frees resources, but none of them matter for sget.