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SubjectRe: [PATCH 2/2] loop : Don't hold the lo_ctl_mutex while fput in loop_clr_fd
On Mon, Apr 28, 2008 at 10:15 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Mon, Apr 28, 2008 at 03:13:09AM +0100, Al Viro wrote:
> > On Mon, Apr 28, 2008 at 10:10:22AM +0800, Dave Young wrote:
> > > [Fixing bug 10504]
> > >
> > > If the bakingfile is a block device file, losetuo -d will trigger lockdep
> > > warning of "circular locking dependency".
> > >
> > > open/release lock order : bdev->bd_mutex ---> lo->lo_ctl_mutex
> > > loop_clr_fd lock order : lo->lo_ctl_mutex ---> bdev->bd_mutex (fput)
> > >
> > > Don't hold the lo_ctl_mutex while fput in loop_clr_fd to fix it. It's safe
> > > because all loop device state will be consistent here.
> >
> > Explain.

Hi, Maybe I have some mis-understood, thanks for pointing out in advance.

IMO the lo_ctl_mutex is for the lo->* state locking, they are all set
to proper values before fput(filp), so I think it's safe to do that.

>
> BTW, explain also why open() at that spot will not do interesting things
> wrt BLKRRPART done a bit below, please.
>

open with a loop device unbound? Sorry, I don't understand. Could you
explain a bit? Thanks

Regards
dave


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