Re: [fuse-devel] Semantics of fuse_notify_delete()

[Nikolaus Rath <Nikolaus@rath.org>]

On Jul 27 2023, Miklos Szeredi via fuse-devel <fuse-devel@lists.sourceforge.net> wrote:
> On Wed, 26 Jul 2023 at 20:09, Nikolaus Rath <Nikolaus@rath.org> wrote:
>>
>> Hello,
>>
>> It seems to me that fuse_notify_delete
>> (https://elixir.bootlin.com/linux/v6.1/source/fs/fuse/dev.c#L1512) fails
>> with ENOTEMPTY if there is a pending FORGET request for a directory
>> entry within. Is that correct?
>
> It's bug if it does that.
>
> The code related to NOTIFY_DELETE in fuse_reverse_inval_entry() seems
> historic.  It's supposed to be careful about mountpoints and
> referenced dentries, but d_invalidate() should have already gotten all
> that out of the way and left an unhashed dentry without any submounts
> or children. The checks just seem redundant, but not harmful.
>
> If you are managing to trigger the ENOTEMPTY case, then something
> strange is going on, and we need to investigate.

I can trigger this reliable on kernel 6.1.0-10-amd64 (Debian stable)
with this sequence of operations:

$ mkdir test
$ echo foo > test/bar
$ Trigger removal of test/bar and then test within the filesystem (not
through unlink()/rmdir() but out-of-band)


What can I do to help with the investigation?

Best,
-Nikolaus