linux-kernel - Re: [PATCH] zram: Fix __zram_bvec

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Message-ID: <20201019152909.rlnhqokqhhauq2kw@linutronix.de>
Date:   Mon, 19 Oct 2020 17:29:09 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-block@...r.kernel.org,
        Mike Galbraith <umgwanakikbuti@...il.com>, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] zram: Fix __zram_bvec_{read,write}() locking order

On 2020-10-19 12:13:53 [+0200], Peter Zijlstra wrote:
> 
> Mikhail reported a lockdep spat detailing how __zram_bvec_read() and
> __zram_bvec_write() use zstrm->lock and zspage->lock in opposite order.
> 
> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>

We have the same patch in RT. I didn't submit it with the other
local-lock patches because this splat pops up once pin_tag() is made a
sleeping lock. I missed the part where migrate_read_lock() can be a
lock. So:

Acked-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Sebastian