From: "J. Bruce Fields" Subject: Re: [Cluster-devel] Re: [PATCH 1/2] dlm: initialize file_lock struct in GETLK before copying conflicting lock Date: Thu, 22 Jan 2009 13:48:48 -0500 Message-ID: <20090122184848.GB15279@fieldses.org> References: <1232555691-29859-1-git-send-email-jlayton@redhat.com> <1232555691-29859-2-git-send-email-jlayton@redhat.com> <20090121234239.GM4295@fieldses.org> <20090122180543.GA23796@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: linux-nfs@vger.kernel.org, lkml@vger.kernel.org, Jeff Layton , nfsv4@linux-nfs.org, cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org To: David Teigland Return-path: In-Reply-To: <20090122180543.GA23796@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfsv4-bounces@linux-nfs.org Errors-To: nfsv4-bounces@linux-nfs.org List-ID: On Thu, Jan 22, 2009 at 12:05:43PM -0600, David Teigland wrote: > On Wed, Jan 21, 2009 at 06:42:39PM -0500, J. Bruce Fields wrote: > > On Wed, Jan 21, 2009 at 11:34:50AM -0500, Jeff Layton wrote: > > > dlm_posix_get fills out the relevant fields in the file_lock before > > > returning when there is a lock conflict, but doesn't clean out any of > > > the other fields in the file_lock. > > > > > > When nfsd does a NFSv4 lockt call, it sets the fl_lmops to > > > nfsd_posix_mng_ops before calling the lower fs. When the lock comes back > > > after testing a lock on GFS2, it still has that field set. This confuses > > > nfsd into thinking that the file_lock is a nfsd4 lock. > > > > I think of the lock system as supporting two types of objects, both > > stored in "struct lock"'s: > > > > - Heavyweight locks: these have callbacks set and the filesystem > > or lock manager could in theory have some private data > > associated with them, so it's important that the appropriate > > callbacks be called when they're released or copied. These > > are what are actually passed to posix_lock_file() and kept on > > the inode lock lists. > > - Lightweight locks: just start, end, pid, flags, and type, with > > everything zeroed out and/or ignored. > > > > I don't see any reason why the lock passed into dlm_posix_get() needs to > > be a heavyweight lock. In any case, if it were, then dlm_posix_get() > > would need to release the passed-in-lock before initializing the new one > > that it's returning. > > It seems the nfs code is mixing those two types up a bit. There may be more cleanup needed. (Pointers welcomed.) > Regardless, the > rationale I see in Jeff's dlm patch is to make the two different locking paths > equivalent: > > Without cfs/dlm, > nfsd4_lockt -> nfsd_test_lock -> vfs_test_lock -> posix_test_lock > > With cfs/dlm, > nfsd4_lockt -> nfsd_test_lock -> vfs_test_lock -> (cfs) -> dlm_posix_get > > When there's a conflict, dlm_posix_get() and posix_test_lock() should do the > same/equivalent things to the fl they are given. > > posix_test_lock() does __locks_copy_lock() on the fl and then sets the pid. > dlm_posix_get() isn't using __locks_copy_lock() because it doesn't have a > conflicting file_lock to copy from. Jeff's patch does nearly the same thing > using locks_init_lock() plus the existing assignments. Right, and that's fine. > But, I think the best solution may be for dlm_posix_get() to set up a > new lightweight file_lock with the values we need, and then call > __locks_copy_lock() with it, just like posix_test_lock(). That sounds like overkill. --b.