From patchwork Mon Jan 27 19:24:06 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "J. Bruce Fields" X-Patchwork-Id: 3543821 Return-Path: X-Original-To: patchwork-linux-nfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id DE698C02DC for ; Mon, 27 Jan 2014 19:24:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0024020131 for ; Mon, 27 Jan 2014 19:24:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED8192011E for ; Mon, 27 Jan 2014 19:24:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753618AbaA0TYJ (ORCPT ); Mon, 27 Jan 2014 14:24:09 -0500 Received: from fieldses.org ([174.143.236.118]:54832 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405AbaA0TYJ (ORCPT ); Mon, 27 Jan 2014 14:24:09 -0500 Received: from bfields by fieldses.org with local (Exim 4.76) (envelope-from ) id 1W7rmw-0001sn-IE; Mon, 27 Jan 2014 14:24:06 -0500 Date: Mon, 27 Jan 2014 14:24:06 -0500 To: "J. Bruce Fields" Cc: linux-nfs@vger.kernel.org Subject: Re: [PATCH 3/3] nfsd4: fix delegation-unlink/rename race Message-ID: <20140127192406.GD17165@fieldses.org> References: <1390769961-30898-1-git-send-email-bfields@redhat.com> <1390769961-30898-4-git-send-email-bfields@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1390769961-30898-4-git-send-email-bfields@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) From: "J. Bruce Fields" Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Sun, Jan 26, 2014 at 03:59:21PM -0500, J. Bruce Fields wrote: > From: "J. Bruce Fields" > > If a file is unlinked or renamed between the time when we do the local > open and the time when we get the delegation, then we will return to the > client indicating that it holds a delegation even though the file no > longer exists under the name it was open under. > > But a client performing an open-by-name, when it is returned a > delegation, must be able to assume that the file is still linked at the > name it was opened under. > > So, hold the parent i_mutex for longer to prevent concurrent renames or > unlinks. > > Signed-off-by: J. Bruce Fields > --- > fs/nfsd/nfs4proc.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c > index 844813a..ef76ba6 100644 > --- a/fs/nfsd/nfs4proc.c > +++ b/fs/nfsd/nfs4proc.c > @@ -279,11 +279,15 @@ do_open_lookup(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, stru > if (open->op_createmode == NFS4_CREATE_EXCLUSIVE && status == 0) > open->op_bmval[1] = (FATTR4_WORD1_TIME_ACCESS | > FATTR4_WORD1_TIME_MODIFY); > - } else { > + } else > + /* > + * Note this may exit with the parent still locked. > + * We will hold the lock until nfsd4_open's final > + * lookup, to prevent renames or unlinks until we've had > + * a chance to an acquire a delegation if appropriate. > + */ > status = nfsd_lookup(rqstp, current_fh, > open->op_fname.data, open->op_fname.len, *resfh); > - fh_unlock(current_fh); > - } > if (status) > goto out; > status = nfsd_check_obj_isreg(*resfh); One last-minute fix: we can now end up taking two i_mutexes. The locking's still correct but we need the following annotation on the parent directory. (I haven't actually seen any lockdep warning trigger here.) --b. --- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index e85b463..a41302a 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -207,7 +207,12 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp, goto out_nfserr; } } else { - fh_lock(fhp); + /* + * In the nfsd4_open() case, this may be held across + * subsequent open and delegation acquisition which may + * need to take the child's i_mutex: + */ + fh_lock_nested(fhp, I_MUTEX_PARENT); dentry = lookup_one_len(name, dparent, len); host_err = PTR_ERR(dentry); if (IS_ERR(dentry))