[dm-devel] Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex
Andrew Morton
akpm at osdl.org
Tue Nov 7 23:00:17 UTC 2006
On Tue, 07 Nov 2006 16:45:07 -0600
Eric Sandeen <sandeen at redhat.com> wrote:
> Andrew Morton wrote:
>
> >> --- linux-2.6.19-rc4.orig/fs/buffer.c 2006-11-07 17:06:20.000000000 +0000
> >> +++ linux-2.6.19-rc4/fs/buffer.c 2006-11-07 17:26:04.000000000 +0000
> >> @@ -188,7 +188,9 @@ struct super_block *freeze_bdev(struct b
> >> {
> >> struct super_block *sb;
> >>
> >> - mutex_lock(&bdev->bd_mount_mutex);
> >> + if (down_trylock(&bdev->bd_mount_sem))
> >> + return -EBUSY;
> >> +
> >
> > This is a functional change which isn't described in the changelog. What's
> > happening here?
>
> Only allow one bdev-freezer in at a time, rather than queueing them up?
>
You're asking me? ;)
Guys, I'm going to park this patch pending a full description of what it
does, a description of what the above hunk is doing and pending an
examination of whether we'd be better off changing the mutex-debugging code
rather than switching to semaphores.
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