Re: [NFS] - do_vfs_lock: VFS is out of sync with lockmanager!

From: Trond Myklebust
Date: Mon Aug 21 2006 - 15:52:44 EST

On Mon, 2006-08-21 at 13:34 +1000, Neil Brown wrote:
> Looking in fs/nfs/file.c (at 2.6.18-rc4-mm1 if it matters, but 2.6.17
> is much the same)
> - do_vfs_lock is only called when the filesystem was mounted with
> -o nolock EXCEPT
> - If a lock request to the server in interrupted (when mounted with
> -o intr) then do_vfs_lock is called to try to get the lock
> locally. Normally equivalent code will be called inside
> fs/lockd/clntproc.c when the server replies that the lock has been
> gained. In the case of an interrupt though this doesn't happen
> but the lock may still have happened on the server. So we record
> locally that the lock was gained, to ensure that it gets unlocked
> when the process exits.
> As you don't have '-o nolocks' you must be hitting the second case.
> The lock call to the server returns -EINTR or -ERESTARTSYS and
> do_vfs_lock is called just-in-case.
> As this is a just-in-case call, it is quite possible that the lock is
> held by some other process, so getting an error is entirely possible.
> So printing the message in this case seems wrong.
> On the other hand, printing the message in any other case seems wrong
> too, as server locking is not being used, so there is nothing to get
> out of sync with.
> As a further complication, I don't think that in the just-in-case
> situation that it should risk waiting for the lock.
> Now maybe we can be sure there is a pending signal which will break
> out of any wait (though I'm worried about -ERESTARTSYS - that doesn't
> imply a signal does it?), but I would feel more comfortable if
> FL_SLEEP were turned off in that path.
> So: Trond: Any obvious errors in the above?
> Is the following patch ok?

Could we instead replace it with a dprintk() that returns the value of
"res"? That will keep it useful for debugging purposes.


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