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

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Message-ID: <CAJfpegsyrSPxLK=nVLDSPWq0dyvoMr+s0K-Lep1BvqX1wpZphA@mail.gmail.com>
Date: Thu, 4 Sep 2025 16:38:32 +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, 4 Sept 2025 at 16:11, Luis Henriques <luis@...lia.com> wrote:
>
> On Thu, Sep 04 2025, Miklos Szeredi wrote:
>
> > 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.
>
> So, your suggesting to have the work queue simply calling this instead of
> walking through the dentries?  (Or even *not* having a work queue at all?)

I think doing in in a work queue is useful, since walking the tree
might take a significant amount of time.

Not having to do the walk manually is definitely a simplification.
It might throw out dentries that got looked up since the last epoch,
but it's probably not a big loss in terms of performance.

Thanks,
Miklos