Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751206Ab3FNETs (ORCPT ); Fri, 14 Jun 2013 00:19:48 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55726 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772Ab3FNETr (ORCPT ); Fri, 14 Jun 2013 00:19:47 -0400 Message-ID: <51BA99CE.8000902@canonical.com> Date: Thu, 13 Jun 2013 23:19:26 -0500 From: Dave Chiluk User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Al Viro CC: Petr Vandrovec , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH] ncpfs: fix rmdir returns Device or resource busy References: <1369781410-24473-1-git-send-email-chiluk@canonical.com> <51A918B8.20303@canonical.com> <51AF9D77.2000901@canonical.com> <51B205A1.4040405@canonical.com> <20130607161452.GI13110@ZenIV.linux.org.uk> <20130613020122.GA20274@ZenIV.linux.org.uk> <20130613064235.GK4165@ZenIV.linux.org.uk> In-Reply-To: <20130613064235.GK4165@ZenIV.linux.org.uk> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3546 Lines: 80 On 06/13/2013 01:42 AM, Al Viro wrote: > On Thu, Jun 13, 2013 at 03:01:22AM +0100, Al Viro wrote: >> On Fri, Jun 07, 2013 at 05:14:52PM +0100, Al Viro wrote: >>> On Fri, Jun 07, 2013 at 11:09:05AM -0500, Dave Chiluk wrote: >>>> Can't you just use the patch from my original e-mail? Anyhow I attached >>>> it an already signed-off patch. >>>> >>>> Al Viro Can you integrate it now? >>> >>> Applied... FWIW, patch directly in mail body is more convenient to deal with. >> >> Actually, looking at that stuff... Why are we bothering with -EBUSY for >> removal of busy directories on ncpfs, anyway? It's not just rmdir(), it's >> overwriting rename() as well. IS_DEADDIR checks in fs/namei.c and fs/readdir.c >> mean that the only method of ncpfs directories that might get called after >> successful removal is ->setattr() and it would be trivial to add the check >> in ncp_notify_change() that would make it fail for dead directories without >> bothering the server at all... >> >> Related question: what happens if you open / unlink / fchmod on ncpfs? > > Speaking of crap used only by ncpfs: I think we can use ->d_iput() to get rid > of d_validate() for good. The only remaining user is ncpfs; what happens there > is that we use the page cache of directory to cache the references to dentries > made by readdir. We could do the following trick: > * have ->d_fsdata for these dentries a pointer into the cache page where > the reference back to dentry is stored > * ->freepage() for those pages consisting of > grab global spinlock > go through all dentries still pointed to by pointers in that > page, zeroing ->d_fsdata > drop the spinlock > * ->d_iput() for those dentries consisting of > grab the same spinlock > if ->d_fsdata is non-zero, store NULL at the address pointed > to by it > drop the spinlock > * ncp_dget_fpos() would > grab that spinlock > check if the reference to dentry in the position we are > interested in is non-NULL > grab ->d_lock > if DCACHE_DENTRY_KILLED is not set > bump ->d_count > drop ->d_lock > drop the spinlock > return dentry > // dentry is doomed > clear the reference > drop ->d_lock > drop the spinlock > return NULL > * ncp_fill_cache() would insert the sucker into cache and set > ->d_fsdata under the same spinlock. > > IOW, instead of wanking with untrusted pointers to dentries, we simply make > sure we clean the pointer when dentry is going away and clean the reference > from dentry to the location of that pointer when the page is going away. > > Objections? I can do a patch along those lines, but I've nothing to test it > on. Had that been cifs, I could at least use samba to test the fucker, but > I've no idea how to do that with ncpfs and I'm not too fond of checking how > much bitrot has mars_nwe suffered... > I'm afraid you are way beyond my current vfs experience level on this one. While you're getting rid of things you might consider dentry_unhash as well, as only hpfs_unlink, ncp_rmdir, and ncp_rename call that. If you get a patch together, I'll do my best to test it. Looks like only ncp_readdir calls that, so afaik, a few varying ls commands should be all that's needed for a test. Dave. p.s. are you sure you don't just want to just deprecate all of ncpfs? -- 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/