linux-kernel - Re: [RFC PATCH v5 2/2] fuse: new work queue to invalidate dentries from old epochs

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Message-ID: <CAJfpegtmmxNozcevgP335nyZui3OAYBkvt-OqA7ei+WTNopbrg@mail.gmail.com>
Date: Thu, 4 Sep 2025 12:35:25 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: Luis Henriques <luis@...lia.com>
Cc: Bernd Schubert <bernd@...ernd.com>, Laura Promberger <laura.promberger@...n.ch>, 
	Dave Chinner <david@...morbit.com>, Matt Harvey <mharvey@...ptrading.com>, 
	linux-fsdevel@...r.kernel.org, kernel-dev@...lia.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v5 2/2] fuse: new work queue to invalidate dentries
 from old epochs

On Thu, 28 Aug 2025 at 18:30, Luis Henriques <luis@...lia.com> wrote:
>
> With the infrastructure introduced to periodically invalidate expired
> dentries, it is now possible to add an extra work queue to invalidate
> dentries when an epoch is incremented.  This work queue will only be
> triggered when the 'inval_wq' parameter is set.
>
> Signed-off-by: Luis Henriques <luis@...lia.com>
> ---
>  fs/fuse/dev.c    |  7 ++++---
>  fs/fuse/dir.c    | 34 ++++++++++++++++++++++++++++++++++
>  fs/fuse/fuse_i.h |  4 ++++
>  fs/fuse/inode.c  | 41 ++++++++++++++++++++++-------------------
>  4 files changed, 64 insertions(+), 22 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index e80cd8f2c049..48c5c01c3e5b 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -2033,13 +2033,14 @@ static int fuse_notify_resend(struct fuse_conn *fc)
>
>  /*
>   * Increments the fuse connection epoch.  This will result of dentries from
> - * previous epochs to be invalidated.
> - *
> - * XXX optimization: add call to shrink_dcache_sb()?

I guess it wouldn't hurt.   Definitely simpler, so I'd opt for this.

>  void fuse_conn_put(struct fuse_conn *fc)
>  {
> -       if (refcount_dec_and_test(&fc->count)) {
> -               struct fuse_iqueue *fiq = &fc->iq;
> -               struct fuse_sync_bucket *bucket;
> -
> -               if (IS_ENABLED(CONFIG_FUSE_DAX))
> -                       fuse_dax_conn_free(fc);
> -               if (fc->timeout.req_timeout)
> -                       cancel_delayed_work_sync(&fc->timeout.work);
> -               if (fiq->ops->release)
> -                       fiq->ops->release(fiq);
> -               put_pid_ns(fc->pid_ns);
> -               bucket = rcu_dereference_protected(fc->curr_bucket, 1);
> -               if (bucket) {
> -                       WARN_ON(atomic_read(&bucket->count) != 1);
> -                       kfree(bucket);
> -               }
> -               if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
> -                       fuse_backing_files_free(fc);
> -               call_rcu(&fc->rcu, delayed_release);
> +       struct fuse_iqueue *fiq = &fc->iq;
> +       struct fuse_sync_bucket *bucket;
> +
> +       if (!refcount_dec_and_test(&fc->count))
> +               return;

Please don't do this.  It's difficult to see what actually changed this way.

Thanks,
Miklos