Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:55907 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368Ab3EUUZm (ORCPT ); Tue, 21 May 2013 16:25:42 -0400 Date: Tue, 21 May 2013 16:25:41 -0400 From: "J. Bruce Fields" To: Steve Dickson Cc: Bruce Fields , Linux NFS Mailing list Subject: Re: [PATCH] NFSD: Don't give out read delegations on exclusive creates Message-ID: <20130521202541.GA13725@fieldses.org> References: <1368643909-8059-1-git-send-email-steved@redhat.com> <20130521192338.GC12114@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20130521192338.GC12114@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, May 21, 2013 at 03:23:38PM -0400, bfields wrote: > On Wed, May 15, 2013 at 02:51:49PM -0400, Steve Dickson wrote: > > When an exclusive create is done with the mode bits > > set (aka open(testfile, O_CREAT | O_EXCL, 0777)) this > > so implicitly O_RDONLY. Is that common? Maybe so, OK. > > > causes a OPEN op followed by a SETATTR op. When a > > read delegation is given in the OPEN, it causes > > the SETATTR to delay with EAGAIN until the > > delegation is recalled. > > > > This patch caused exclusive creates to give out > > a write delegation (which turn into no delegation) > > which allows the SETATTR seamlessly succeed. > > OK. May as well make it apply to all creates, though, I think? > Any create flag seems like a sign the file's likely to be modified soon, > hence isn't a good candidate for a read delegation. That would look like the following. --b. commit 3f47b6220ca6b08a7ab86baaaab87389707a3308 Author: Steve Dickson Date: Wed May 15 14:51:49 2013 -0400 NFSD: Don't give out read delegations on exclusive creates When an exclusive create is done with the mode bits set (aka open(testfile, O_CREAT | O_EXCL, 0777)) this causes a OPEN op followed by a SETATTR op. When a read delegation is given in the OPEN, it causes the SETATTR to delay with EAGAIN until the delegation is recalled. This patch caused exclusive creates to give out a write delegation (which turn into no delegation) which allows the SETATTR seamlessly succeed. Signed-off-by: Steve Dickson [bfields: do this for any CREATE, not just exclusive; comment] Signed-off-by: J. Bruce Fields diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index c4f6339..44dcea9 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -3113,8 +3113,17 @@ nfs4_open_delegation(struct net *net, struct svc_fh *fh, goto out; if (!cb_up || !(oo->oo_flags & NFS4_OO_CONFIRMED)) goto out; + /* + * Also, if the file was opened for write or + * create, there's a good chance the client's + * about to write to it, resulting in an + * immediate recall (since we don't support + * write delegations): + */ if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) flag = NFS4_OPEN_DELEGATE_WRITE; + else if (open->op_create == NFS4_OPEN_CREATE) + flag = NFS4_OPEN_DELEGATE_WRITE; else flag = NFS4_OPEN_DELEGATE_READ; break;