linux-kernel - Re: [RFC PATCH v2 4/6] fuse: implementation of the FUSE_LOOKUP

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Message-ID: <87ldi64sh4.fsf@wotan.olymp>
Date: Fri, 09 Jan 2026 17:16:07 +0000
From: Luis Henriques <luis@...lia.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: Bernd Schubert <bschubert@....com>,  Amir Goldstein
 <amir73il@...il.com>,  "Darrick J. Wong" <djwong@...nel.org>,  Kevin Chen
 <kchen@....com>,  Horst Birthelmer <hbirthelmer@....com>,
  linux-fsdevel@...r.kernel.org,  linux-kernel@...r.kernel.org,  Matt
 Harvey <mharvey@...ptrading.com>,  kernel-dev@...lia.com
Subject: Re: [RFC PATCH v2 4/6] fuse: implementation of the
 FUSE_LOOKUP_HANDLE operation

On Fri, Jan 09 2026, Miklos Szeredi wrote:

> On Fri, 9 Jan 2026 at 16:56, Bernd Schubert <bschubert@....com> wrote:
>
>> Feasible, but we should extend io-uring to FUSE_NOTIFY first, otherwise
>> this will have a painful overhead.
>
> We don't want to do the lock/add/unlock for individual dentries
> anyway, so might as well make this FUSE_NOTIFY_ENTRIES.  That would
> lock the directory, add a bunch of dentries, then unlock.
>
> The fun part is that locking the directory must not be done from the
> READDIR context, as rwsem read locks are apparently not nestable.
> This would make the interface a pain to use.  We could work around
> that by checking if a READDIR is currently in progress and then
> synchronizing the two such that the entries are added with the
> directory lock held.   It's a bit of complexity, but maybe worth it as
> it's going to be the common usage.

Yikes!  Things are not getting any simpler :-(

OK, looks like there's a lot of things I'll need to figure out before
proceeding.

/me schedules some time to learn and play a bit with all this.

Cheers,
-- 
Luís