linux-kernel - Re: [PATCH] block: mq flush: fix race between IPI handler and mq flush worker

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Message-ID: <20140519151824.GA21762@lst.de>
Date:	Mon, 19 May 2014 17:18:24 +0200
From:	Christoph Hellwig <hch@....de>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] block: mq flush: fix race between IPI handler and mq
	flush worker

On Mon, May 19, 2014 at 11:05:50PM +0800, Ming Lei wrote:
> Another simple fix is to disable ipi for flush request, but looks
> this one should be better.

I think the first thing is to bite the bullet and sort out and document
the various unions in struct request for real.

For example the first union has the call_single_data for the blk-mq
completions, while the second one has the ipi_list that is used by
the old blk-softirq code.

If we get this right with a single union that contains a struct for
each phase of the request we might find enough space to keep using
the current way.

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