linux-kernel - Re: [GIT PULL] fuse update for 6.19

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Message-ID: <CAHk-=wht097GMgEuH870PU4dMfBCinZ5_qvxpqK2Q9PP=QRdTA@mail.gmail.com>
Date: Fri, 5 Dec 2025 15:47:50 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] fuse update for 6.19

On Thu, 4 Dec 2025 at 00:25, Miklos Szeredi <miklos@...redi.hu> wrote:
>
> The stale dentry cleanup has a patch touching dcache.c: this extracts
> a helper from d_prune_aliases() that puts the unused dentry on a
> dispose list.  Export this and shrink_dentry_list() to modules.

Is that

        spin_lock(&dentry->d_lock);
        if (!dentry->d_lockref.count)
                to_shrink_list(dentry, dispose);
        spin_unlock(&dentry->d_lock);

thing possibly hot, and count might be commonly non-zero?

Because it's possible that we could just make it a lockref operation
where we atomically don't take the lock if the count is non-zero so
that we don't unnecessarily move cachelines around...

IOW, some kind of "lockref_lock_if_zero()" pattern?

I have no idea what the fuse dentry lifetime patterns might be, maybe
this is a complete non-issue...

         Linus