From: Al Viro <viro@ZenIV.linux.org.uk>
To: NeilBrown <neilb@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] VFS: close race between getcwd() and d_move()
Date: Tue, 21 Nov 2017 23:50:58 +0000 [thread overview]
Message-ID: <20171121235057.GA19523@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20171110205328.GH21978@ZenIV.linux.org.uk>
On Fri, Nov 10, 2017 at 08:53:28PM +0000, Al Viro wrote:
> On Fri, Nov 10, 2017 at 03:45:41PM +1100, NeilBrown wrote:
> > -void __d_drop(struct dentry *dentry)
> > +static void ___d_drop(struct dentry *dentry)
> > {
> > if (!d_unhashed(dentry)) {
> > struct hlist_bl_head *b;
> > @@ -486,12 +488,15 @@ void __d_drop(struct dentry *dentry)
> >
> > hlist_bl_lock(b);
> > __hlist_bl_del(&dentry->d_hash);
> > - dentry->d_hash.pprev = NULL;
> > hlist_bl_unlock(b);
> > /* After this call, in-progress rcu-walk path lookup will fail. */
> > write_seqcount_invalidate(&dentry->d_seq);
> > }
> > }
> > +void __d_drop(struct dentry *dentry) {
> > + ___d_drop(dentry);
> > + dentry->d_hash.pprev = NULL;
>
> Umm... That reordering (unhashed vs. ->d_seq) might be a problem
> on the RCU side. I'm not sure it is, we might get away with that,
> actually, but I want to finish digging through the pathwalk-related
> code. Cursing it for being too subtle for its own good, as usual...
OK, I believe that it's survivable, but I'd prefer to keep in -next
for a while and give it more testing.
next prev parent reply other threads:[~2017-11-21 23:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-09 3:22 [PATCH 0/3] Three VFS patch resends NeilBrown
2017-11-09 3:22 ` [PATCH 1/3] VFS: use synchronize_rcu_expedited() in namespace_unlock() NeilBrown
2017-11-09 3:22 ` [PATCH 2/3] Improve fairness when locking the per-superblock s_anon list NeilBrown
2017-11-09 19:52 ` Linus Torvalds
2017-11-09 20:50 ` Al Viro
2017-11-09 23:09 ` NeilBrown
2017-11-09 23:19 ` Al Viro
2017-11-10 0:02 ` Linus Torvalds
2017-11-10 8:50 ` Christoph Hellwig
2017-11-09 3:22 ` [PATCH 3/3] VFS: close race between getcwd() and d_move() NeilBrown
2017-11-09 11:41 ` Nikolay Borisov
2017-11-09 13:08 ` Matthew Wilcox
2017-11-09 16:02 ` Nikolay Borisov
2017-11-09 20:23 ` Linus Torvalds
2017-11-09 22:14 ` NeilBrown
2017-11-10 1:40 ` Linus Torvalds
2017-11-10 4:45 ` NeilBrown
2017-11-10 19:52 ` Linus Torvalds
2017-11-10 20:53 ` Al Viro
2017-11-21 23:50 ` Al Viro [this message]
2017-11-22 1:31 ` NeilBrown
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