Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-pb0-f46.google.com ([209.85.160.46]:58331 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753778Ab2K3CeC (ORCPT ); Thu, 29 Nov 2012 21:34:02 -0500 Received: by mail-pb0-f46.google.com with SMTP id wy7so90932pbc.19 for ; Thu, 29 Nov 2012 18:34:01 -0800 (PST) Message-ID: <50B81B11.7050704@gaikai.com> Date: Thu, 29 Nov 2012 18:33:53 -0800 From: Patrick McLean MIME-Version: 1.0 To: Al Viro CC: Patrick McLean , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Trond Myklebust , linux-nfs@vger.kernel.org Subject: Re: Regression with initramfs and nfsroot (appears to be in the dcache) References: <20121129213316.GU4939@ZenIV.linux.org.uk> <20121129222109.GW4939@ZenIV.linux.org.uk> <50B7E759.9070007@gaikai.com> <20121129234326.GX4939@ZenIV.linux.org.uk> <50B7FBA7.2030300@gaikai.com> <20121130003502.GY4939@ZenIV.linux.org.uk> <50B8046F.7030308@cim.mcgill.ca> <20121130013628.GZ4939@ZenIV.linux.org.uk> <50B811BA.6070503@cim.mcgill.ca> <20121130020047.GA4939@ZenIV.linux.org.uk> In-Reply-To: <20121130020047.GA4939@ZenIV.linux.org.uk> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 29/11/12 06:00 PM, Al Viro wrote: > On Thu, Nov 29, 2012 at 05:54:02PM -0800, Patrick McLean wrote: >>> Very interesting. Do you have anything mounted on the corresponding >>> directories on server? The picture looks like you are getting empty >>> fhandles in readdir+ respons for exactly the same directories that happen >>> to be mountpoints on client. In any case, we shouldn't do that blind >>> d_drop() - empty fhandles can happen. The only remaining question is >>> why do they happen on that set of entries. From my reading of >>> encode_entryplus_baggage() it looks like we have compose_entry_fh() >>> failing for those entries and those entries alone. One possible cause >>> would be d_mountpoint(dchild) being true on server. If it is true, we >>> can declare the case closed; if not, I really wonder what's going on. >> >> Those directories do have the server's own copies of the said directories bind mounted at the moment in a separate mount namespace. >> >> Unmounting those directories on the server does appear to stop the WARN_ON from triggering. > > OK, that settles it. WARN_ON() and printks in the area can be dropped; > the right fix is below. However, there's a similar place in cifs that > also needs to be dealt with and I really, really wonder why the hell do > we do d_drop() in nfs_revalidate_lookup(). It's not relevant in this > bug, but I would like to understand what's wrong with simply returning > 0 from ->d_revalidate() and letting the caller (in fs/namei.c) take care > of unhashing, etc. itself. Would make have_submounts() in there pointless > as well - we could just return 0 and let d_invalidate() take care of the > checks... Trond? > > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > --- a/fs/nfs/dir.c > +++ b/fs/nfs/dir.c > @@ -450,7 +450,8 @@ void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry) > nfs_refresh_inode(dentry->d_inode, entry->fattr); > goto out; > } else { > - d_drop(dentry); > + if (d_invalidate(dentry) != 0) > + goto out; > dput(dentry); > } > } Excellent, thanks. Is there any chance this will make it to 3.7? Also we might want to cc stable@ on this as well since it is a regression in 3.6.