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SubjectRe: [PATCH] loop: fput() called in loop_clr_fd() may cause bd_mutex recursive locking
On (12/17/11 22:58), Al Viro wrote:
> On Sun, Dec 18, 2011 at 01:37:45AM +0300, Sergey Senozhatsky wrote:
> > > Think of it for a minute - if we could run into the
> > > same bdev in that recursion, what would have happened on read() from
> > > that sucker? So yes, it is a false positive.
> >
> > I've tried read()/write() some time ago and it worked. Perhaps, I just
> > wasn't "lucky" enough to hit any problems.
>
> Sure - exactly because of that loop prevention logics. *If* we really
> had been able to set a loop0 -> loop1 -> loop2 -> loop0 or something of
> that sort, this warning wouldn't be a false positive. But on any
> such setup, where would IO attempts end up doing?

Thanks for your explanations.

> IOW, we have to prevent such setups anyway and not just because of
> problems on close() - they would be deadly on read() and write()...
>

Preventing recursion in the first place? For example, in lo_open()?


Sergey


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