From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: fs: lockup on rename_mutex in fs/dcache.c:1035 Date: Sun, 26 Oct 2014 23:42:30 +0000 Message-ID: <20141026234230.GU7996@ZenIV.linux.org.uk> References: <544C50CB.4090408@oracle.com> <87siibttyi.fsf@x220.int.ebiederm.org> <20141026030608.GN7996@ZenIV.linux.org.uk> <20141026035100.GO7996@ZenIV.linux.org.uk> <20141026035705.GP7996@ZenIV.linux.org.uk> <20141026191332.GS7996@ZenIV.linux.org.uk> <20141026215742.GT7996@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sasha Levin , linux-fsdevel , LKML , Dave Jones , "Eric W. Biederman" To: Linus Torvalds Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Sun, Oct 26, 2014 at 04:33:11PM -0700, Linus Torvalds wrote: > On Sun, Oct 26, 2014 at 2:57 PM, Al Viro wrote: > > .. snip .. > > in d_walk(), __list_del() instead of list_del() in __dentry_kill(), d_u.d_child > > turning into d_child everywhere, while d_alias turns into d_u.d_alias... > > > > It looks like that way we would get no retries on the second pass. Comments? > > Since I missed the whole issue with d_child.next, I'm not sure any > comments from me would be helpful. > > It does sound like trying to be more careful with d_child and using > d_alias instead is a good idea. d_alias is only used under the dentry > lock, and not in any horribly subtle situations, right? So that sounds > like a good change regardless of this particular fix - making the > union happen in a less nasty place.. OK... See vfs.git#experimental-d_walk - the first commit there moves d_rcu from d_child to d_alias, the second is basically "skip the killed siblings rather than restarting the tree walk".