linux-kernel - Re: [PATCH 3/3] blk-mq: Use llist_head for blk_cpu

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Message-ID: <20201029145743.GA19379@infradead.org>
Date:   Thu, 29 Oct 2020 14:57:43 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Christoph Hellwig <hch@...radead.org>, linux-block@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        David Runge <dave@...epmap.de>, linux-rt-users@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Wagner <dwagner@...e.de>,
        Mike Galbraith <efault@....de>,
        Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH 3/3] blk-mq: Use llist_head for blk_cpu_done

On Thu, Oct 29, 2020 at 03:56:23PM +0100, Sebastian Andrzej Siewior wrote:
> On 2020-10-29 14:05:36 [+0000], Christoph Hellwig wrote:
> > Well, usb-storage obviously seems to do it, and the block layer
> > does not prohibit it.
> 
> Also loop, nvme-tcp and then I stopped looking.
> Any objections about adding local_bh_disable() around it?

To me it seems like the whole IPI plus potentially softirq dance is
a little pointless when completing from process context.

Sagi, any opinion on that from the nvme-tcp POV?