Re: [PATCH 2/2] loop : Don't hold the lo_ctl_mutex while fput inloop_clr_fd

[Al Viro]

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.

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