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 for linux-mtd@lists.infradead.org; Wed, 05 Mar 2014 21:50:21 +0000
From: Bill Pringlemeir <bpringlemeir@nbsps.com>
To: Richard Weinberger <richard@nod.at>
Subject: Re: UBI leb_write_unlock NULL pointer Oops (continuation)
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Date: Wed, 05 Mar 2014 16:42:12 -0500
In-Reply-To: <87txbcib93.fsf@nbsps.com> (Bill Pringlemeir's message of "Wed,
 05 Mar 2014 16:30:48 -0500")
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Cc: "Wiedemer, Thorsten \(Lawo AG\)" <Thorsten.Wiedemer@lawo.com>,
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On  5 Mar 2014, bpringlemeir@nbsps.com wrote:

> On  5 Mar 2014, richard@nod.at wrote:

>> The solution is rather trivial.

[snip]

> Still, the logic of ubi_eba_copy_leb() seems really weird to me.  I
> don't understand,

> It looks like a double reference count decrement.  Maybe they operate on
> different ltree nodes, but then the locks mis-match.

	if (down_write_trylock(&le->mutex))
		return 0;

Ah, I mis-understood.  The path where the lock is taken doesn't
decrement the 'users' count; I was thinking of '0' as fail.

Regards,
Bill Pringlemeir.