From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 23 Oct 2017 18:43:16 +0800 From: Ming Lei To: Christoph Hellwig Cc: axboe@kernel.dk, linux-block@vger.kernel.org Subject: Re: [PATCH v2] block: fix peeking requests during PM Message-ID: <20171023104315.GA30252@ming.t460p> References: <20171020144523.4585-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20171020144523.4585-1-hch@lst.de> List-ID: On Fri, Oct 20, 2017 at 04:45:23PM +0200, Christoph Hellwig wrote: > We need to look for an active PM request until the next softbarrier > instead of looking for the first non-PM request. Otherwise any cause > of request reordering might starve the PM request(s). Hi Christoph, Could you share us how the starve is caused? Looks all PM request is run via scsi_execute(), and the caller is always waiting for the completion of PM request. Especially PM request is run after SCSI device is in quiesce state, during that time, no normal(non-preempt) request can enter queue after the making quiesce safe patchset is merged. -- Ming