linux-kernel - Re: nfsd changes for 2.6.37

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Date:	Tue, 26 Oct 2010 18:41:07 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Bryan Schumaker <bjschuma@...app.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: nfsd changes for 2.6.37

On Tue, Oct 26, 2010 at 06:11:56PM -0400, J. Bruce Fields wrote:
> On Tue, Oct 26, 2010 at 05:44:41PM -0400, J. Bruce Fields wrote:
> > On Tue, Oct 26, 2010 at 02:37:26PM -0700, Linus Torvalds wrote:
> > > On Tue, Oct 26, 2010 at 2:24 PM, J. Bruce Fields <bfields@...ldses.org> wrote:
> > > >
> > > > I did a couple connectathon runs just now with no obvious ill effects
> > > > except for some sleep-within-spinlock warnings in the lease code.
> > > 
> > > Hmm. Those sleep-within-spinlock warnings are very likely serious
> > > bugs.
> > 
> > Yeah, didn't mean to belittle them.
> > 
> > > Can you quote the whole warning with stack trace?
> > 
> > It's just obvious allocations in setlease:
> > 
> > BUG: sleeping function called from invalid context at mm/slab.c:3101
> > in_atomic(): 1, irqs_disabled(): 0, pid: 4345, name: lease_tests
> > 1 lock held by lease_tests/4345:
> >  #0:  (file_lock_lock){+.+.+.}, at: [<ffffffff81128be5>] lock_flocks+0x15/0x20
> > Pid: 4345, comm: lease_tests Not tainted 2.6.36-05858-gbd5e20b #1028
> > Call Trace:
> >  [<ffffffff8103141d>] __might_sleep+0x10d/0x140
> >  [<ffffffff810e3ad3>] kmem_cache_alloc+0x1f3/0x230
> >  [<ffffffff8112a4d2>] generic_setlease+0x112/0x2c0
> >  [<ffffffff8112a6b5>] __vfs_setlease+0x35/0x40
> >  [<ffffffff8112acfe>] fcntl_setlease+0xce/0x180
> >  [<ffffffff810f7c2e>] sys_fcntl+0x2fe/0x630
> >  [<ffffffff81961999>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> >  [<ffffffff81002658>] system_call_fastpath+0x16/0x1b
> > 
> > I'm testing a patch.
> 
> This works for me.
> 
> I'm not saying it's correct, but it does at least pass my dumb tests
> without complaining.

I can't think of any more missing locking, though I did notice this on a
quick look.

--b.

commit fc42117585672abd3cbf247dd311869233d1606a
Author: J. Bruce Fields <bfields@...hat.com>
Date:   Tue Oct 26 18:25:30 2010 -0400

    fix nlmsvc_notify_blocked locking
    
    Signed-off-by: J. Bruce Fields <bfields@...hat.com>

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 6f1ef00..c462d34 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -700,14 +700,16 @@ nlmsvc_notify_blocked(struct file_lock *fl)
 	struct nlm_block	*block;
 
 	dprintk("lockd: VFS unblock notification for block %p\n", fl);
+	spin_lock(&nlm_blocked_lock);
 	list_for_each_entry(block, &nlm_blocked, b_list) {
 		if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
-			nlmsvc_insert_block(block, 0);
+			nlmsvc_insert_block_locked(block, 0);
+			spin_unlock(&nlm_blocked_lock);
 			svc_wake_up(block->b_daemon);
 			return;
 		}
 	}
-
+	spin_unlock(&nlm_blocked_lock);
 	printk(KERN_WARNING "lockd: notification for unknown block!\n");
 }
 
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