Re: [PATCH 9/14] lockd: handle fl_notify callbacks

["J. Bruce Fields" <bfields@fieldses.org>]

On Sat, Feb 03, 2007 at 04:40:05PM -0800, Trond Myklebust wrote:
> On Sat, 2007-02-03 at 00:34 -0500, J. Bruce Fields wrote:
> >  nlmsvc_notify_blocked(struct file_lock *fl, struct file_lock *conf, int result)
> >  {
> >  	struct nlm_block	*block;
> > +	int rc = -ENOENT;
> >  
> >  	dprintk("lockd: nlmsvc_notify_blocked lock %p conf %p result %d\n",
> >  							fl, conf, result);
> > +	lock_kernel();
> >  	list_for_each_entry(block, &nlm_blocked, b_list) {
> >  		if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
> > +			dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
> > +							block, block->b_flags);
> > +			if (block->b_flags & B_QUEUED) {
> > +				if (block->b_flags & B_TOO_LATE) {
> > +					rc = -ENOLCK;
> > +					break;
> > +				}
> > +				nlmsvc_update_deferred_block(block, conf, result);
> 
> but nlmsvc_update_deferred_block() can sleep!

Yep, you're right.  Fortunately, the only reason it sleeps is a single
allocation that's probably easy enough to do elsewhere, which I believe
would fix this:

> How are you protecting against races with notification? Also, how are
> you guaranteeing that the block queue won't change underneath you when
> you lose the BKL.

--b.

-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier.
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs