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

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Message-ID: <20251206022826.GP1712166@ZenIV>
Date: Sat, 6 Dec 2025 02:28:26 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Miklos Szeredi <miklos@...redi.hu>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] fuse update for 6.19

On Fri, Dec 05, 2025 at 05:52:51PM -0800, Linus Torvalds wrote:
> On Fri, 5 Dec 2025 at 17:42, Al Viro <viro@...iv.linux.org.uk> wrote:
> >
> > Far more interesting question, IMO, is what's to prevent memory
> > pressure from evicting the damn argument right under us.
> 
> That was my first reaction, but look at the 'fuse_dentry_prune()' logic.
> 
> So if the dentry is removed by the VFS layer, it should be removed here too.

Sure, ->d_prune() would take it out of the rbtree, but what if it hits
                                rb_erase(&fd->node, &dentry_hash[i].tree);
                                RB_CLEAR_NODE(&fd->node);
                                spin_unlock(&dentry_hash[i].lock);
... right here, when we are not holding any locks anymore?
                                d_dispose_if_unused(fd->dentry, &dispose);
                                cond_resched();
                                spin_lock(&dentry_hash[i].lock);