From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([174.143.236.118]:50171 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825Ab1IUPB6 (ORCPT ); Wed, 21 Sep 2011 11:01:58 -0400 Date: Wed, 21 Sep 2011 11:01:57 -0400 To: "J. Bruce Fields" Cc: linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, samba-technical@lists.samba.org, Christoph Hellwig , Al Viro , Mimi Zohar Subject: Re: [PATCH 2/6] leases: fix write-open/read-lease race Message-ID: <20110921150157.GA21510@fieldses.org> References: <1316617097-21384-1-git-send-email-bfields@redhat.com> <1316617097-21384-3-git-send-email-bfields@redhat.com> Content-Type: text/plain; charset=us-ascii In-Reply-To: <1316617097-21384-3-git-send-email-bfields@redhat.com> From: "J. Bruce Fields" Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Wed, Sep 21, 2011 at 10:58:13AM -0400, J. Bruce Fields wrote: > In setlease, we use i_writecount to decide whether we can give out a > read lease. > > In open, we break leases before incrementing i_writecount. > > There is therefore a window between the break lease and the i_writecount > increment when setlease could add a new read lease. > > This would leave us with a simultaneous write open and read lease, which > shouldn't happen. And maybe someone that knows the open code better than me could confirm whether it's reasonable to move the break_lease() call to __dentry_open like this.... --b. > > Signed-off-by: J. Bruce Fields > --- > fs/namei.c | 5 +---- > fs/open.c | 4 ++++ > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/fs/namei.c b/fs/namei.c > index 2826db3..6ff59e5 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -2044,10 +2044,7 @@ static int may_open(struct path *path, int acc_mode, int flag) > if (flag & O_NOATIME && !inode_owner_or_capable(inode)) > return -EPERM; > > - /* > - * Ensure there are no outstanding leases on the file. > - */ > - return break_lease(inode, flag); > + return 0; > } > > static int handle_truncate(struct file *filp) > diff --git a/fs/open.c b/fs/open.c > index f711921..22c41b5 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -685,6 +685,10 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt, > if (error) > goto cleanup_all; > > + error = break_lease(inode, f->f_flags); > + if (error) > + goto cleanup_all; > + > if (!open && f->f_op) > open = f->f_op->open; > if (open) { > -- > 1.7.4.1 >