linux-kernel - Re: [PATCH] mm/zpool: use workqueue for zpool

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Message-Id: <20160425144621.07f246158845fc08815c39dd@linux-foundation.org>
Date:	Mon, 25 Apr 2016 14:46:21 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dan Streetman <ddstreet@...e.org>
Cc:	Yu Zhao <yuzhao@...gle.com>, Seth Jennings <sjenning@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	Nitin Gupta <ngupta@...are.org>, Linux-MM <linux-mm@...ck.org>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dan Streetman <dan.streetman@...onical.com>
Subject: Re: [PATCH] mm/zpool: use workqueue for zpool_destroy

On Mon, 25 Apr 2016 17:20:10 -0400 Dan Streetman <ddstreet@...e.org> wrote:

> Add a work_struct to struct zpool, and change zpool_destroy_pool to
> defer calling the pool implementation destroy.
> 
> The zsmalloc pool destroy function, which is one of the zpool
> implementations, may sleep during destruction of the pool.  However
> zswap, which uses zpool, may call zpool_destroy_pool from atomic
> context.  So we need to defer the call to the zpool implementation
> to destroy the pool.
> 
> This is essentially the same as Yu Zhao's proposed patch to zsmalloc,
> but moved to zpool.

OK, but the refrain remains the same: what are the runtime effects of
the change?  Are real people in real worlds seeing scary kernel
warnings?  Deadlocks?

This info is needed so that I and others can decide which kernel
version(s) should be patched.

Thanks.