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Subject: Re: [PATCH] nvmet: disable direct I/O when unavailable
To:     Johannes Thumshirn <jthumshirn@suse.de>,
        Max Gurtovoy <maxg@mellanox.com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        Christoph Hellwig <hch@lst.de>
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        Linux NVMe Mailinglist <linux-nvme@lists.infradead.org>
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From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <a85e85d6-6a06-7663-3a12-710b6467dedd@acm.org>
Date:   Mon, 25 Feb 2019 06:49:04 -0800
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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:

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

Bart.