On Wednesday, 8 November 2006 00:18, Eric Sandeen wrote:
> Rafael J. Wysocki wrote:
> > On Tuesday, 7 November 2006 23:45, Eric Sandeen 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?
> >
> > But freeze_bdev() is supposed to return the result of get_super(bdev)
> > _unconditionally_. Moreover, in its current form freeze_bdev() _cannot_
> > _fail_, so I don't see how this change doesn't break any existing code.
>
> Well, it could return NULL. Is that a failure?
It will only fail if get_super(bdev) returns NULL, but if you call
freeze_bdev(sb->s_bdev), then it can't do that.
> But, nobody is checking for an outright error, certainly. Especially
> when the error hasn't been ERR_PTR'd. :) So I agree, that's not so good.
>
> But, how is a stampede of fs-freezers -supposed- to work? I could
> imagine something like a freezer count, and the filesystem is only
> unfrozen after everyone has thawed? Or should only one freezer be
> active at a time... which is what we have now I guess.
I think it shouldn't be possible to freeze an fs more than once.
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