Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752453Ab3IENXd (ORCPT ); Thu, 5 Sep 2013 09:23:33 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:60316 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751625Ab3IENXb (ORCPT ); Thu, 5 Sep 2013 09:23:31 -0400 Date: Thu, 5 Sep 2013 14:23:25 +0100 From: Al Viro To: Miklos Szeredi Cc: Linux-Fsdevel , Kernel Mailing List , "mszeredi@suse.cz" , David Howells , Steven Whitehouse , Trond Myklebust , Greg Kroah-Hartman Subject: Re: [PATCH 04/11] vfs: check unlinked ancestors before mount Message-ID: <20130905132325.GQ13318@ZenIV.linux.org.uk> References: <1378374284-1484-1-git-send-email-miklos@szeredi.hu> <1378374284-1484-5-git-send-email-miklos@szeredi.hu> <20130905111852.GP13318@ZenIV.linux.org.uk> <20130905120230.GA21170@tucsk.piliscsaba.szeredi.hu> <20130905123911.GA25538@tucsk.piliscsaba.szeredi.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130905123911.GA25538@tucsk.piliscsaba.szeredi.hu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1430 Lines: 36 On Thu, Sep 05, 2013 at 02:39:11PM +0200, Miklos Szeredi wrote: > +static bool __has_unlinked_ancestor(struct dentry *dentry) > +{ > + struct dentry *this; > + > + for (this = dentry; !IS_ROOT(this); this = this->d_parent) { > + int is_unhashed; > + > + /* Need exclusion wrt. check_submounts_and_drop() */ > + spin_lock(&this->d_lock); > + is_unhashed = d_unhashed(this); > + spin_unlock(&this->d_lock); > + > + if (is_unhashed) > + return true; > + } > + return false; > +} I still don't get it; why do you need to bother with early setting of DCACHE_MOUNTED? You are grabbing rename_lock for write in d_set_mounted(). What kind of races with check for submounts are you worried about? d_walk() will rescan everything if something grabs rename_lock for write while it had been running, so just fold the "have nothing in d_subdir" case of check_submounts_and_drop() into d_walk() and be done with that... What's the problem with such variant? AFAICS, all you need to care about is d_set_mounted() not getting between the scan for submounts and actual __d_drop() and your "finish" callback is called only after d_walk() having grabbed d_lock *and* rechecked rename_lock. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/