linux-kernel - Re: [PATCH] nvmet: disable direct I/O when unavailable

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Message-ID: <20190225153827.GA17442@linux-x5ow.site>
Date:   Mon, 25 Feb 2019 16:38:27 +0100
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Max Gurtovoy <maxg@...lanox.com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        Christoph Hellwig <hch@....de>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux NVMe Mailinglist <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH] nvmet: disable direct I/O when unavailable

On Mon, Feb 25, 2019 at 06:49:04AM -0800, Bart Van Assche wrote:
> On 2/25/19 1:37 AM, Johannes Thumshirn wrote:
> > On 24/02/2019 11:54, Max Gurtovoy wrote:
> > > What is the status of iSCSI/SRP targets in this case ?
> > 
> > iSCSI/SRP passes in the following:
> > 
> >   /*
> >    * Use O_DSYNC by default instead of O_SYNC to forgo syncing
> >    * of pure timestamp updates.
> >    */
> >   flags = O_RDWR | O_CREAT | O_LARGEFILE | O_DSYNC;
> 
> That code fragment comes from the LIO file backend. There is no requirement
> for a SCSI target core file backend to use O_DSYNC. SCST allows users to
> choose whether or not O_DSYNC should be used:

Yes, LIO file backend is the in-tree equivalent to NVMe's file backend. That's
why I copied it here.


> 
> 	if (virt_dev->wt_flag && !virt_dev->nv_cache)
> 		open_flags |= O_DSYNC;
> 

OK. Do your open_flags include O_DIRECT per default as well?

Byte,
	Johannes
-- 
Johannes Thumshirn                            SUSE Labs Filesystems
jthumshirn@...e.de                                +49 911 74053 689
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