Return-Path: Received: from mail-out1.uio.no ([129.240.10.57]:43799 "EHLO mail-out1.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755727Ab0EXQVb (ORCPT ); Mon, 24 May 2010 12:21:31 -0400 Subject: Re: [PATCH] VFS: fix recent breakage of FS_REVAL_DOT From: Trond Myklebust To: Al Viro Cc: Neil Brown , Chuck Lever , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20100524155031.GQ31073@ZenIV.linux.org.uk> References: <20100524165756.2cfa54c4@notabene.brown> <20100524115903.GP31073@ZenIV.linux.org.uk> <20100524155031.GQ31073@ZenIV.linux.org.uk> Content-Type: text/plain; charset="UTF-8" Date: Mon, 24 May 2010 12:21:22 -0400 Message-ID: <1274718082.10795.31.camel@heimdal.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Mon, 2010-05-24 at 16:50 +0100, Al Viro wrote: > On Mon, May 24, 2010 at 12:59:03PM +0100, Al Viro wrote: > > > BTW, here's a question for nfs client folks: is it true that for any two > > pathnames on _client_ resolving to pairs (mnt1, dentry) and (mnt2, dentry) > > resp., nfs_devname(mnt1, dentry, ...) and nfs_devname(mnt2, dentry, ...) > > should yield the strings that do not differ past the ':' (i.e. that the > > only possible difference is going to be in spelling the server name)? > > Actually, there's a related one: suppose we have two mounts from the same > server, with the same flags, etc., ending up sharing a dentry on client. > What will we get from GETATTR asking for fs_locations, in fs_root field? > > Can an nfs4 server e.g. have /x/y being a symlink that resolves to /a/b and > allow mounting of both /x/y/c and /a/b/c? Which path would it return to > client that has mounted both, walked to some referral point and called > nfs_do_refmount(), triggering nfs4_proc_fs_locations()? > > Trond, Neil? When mounting /x/y/c in your example above, the NFSv4 protocol requires the client itself to resolve the symlink, and then walk down /a/b/c (looking up component by component), so it will in practice not see anything other than /a/b/c. If it walks down to a referral, and then calls nfs_do_refmount, it will do the same thing: obtain a path /e/f/g on the new server, and then walk down that component by component while resolving any symlinks and/or referrals that it crosses in the process. Cheers Trond