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Subject: Re: [resend v1 5/5] drivers/scsi/sd.c: Convert to use
 disk_set_capacity
From:   "Ewan D. Milne" <emilne@redhat.com>
To:     "Martin K. Petersen" <martin.petersen@oracle.com>,
        James Bottomley <jejb@linux.ibm.com>
Cc:     axboe@kernel.dk, Chaitanya.Kulkarni@wdc.com, mst@redhat.com,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, ssomesh@amazon.com,
        Balbir Singh <sblbir@amazon.com>, hch@lst.de
Date:   Tue, 07 Jan 2020 16:37:43 -0500
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On Mon, 2020-01-06 at 23:39 -0500, Martin K. Petersen wrote:
> James,
> 
> > > We already emit an SDEV_EVT_CAPACITY_CHANGE_REPORTED event if device
> > > capacity changes. However, this event does not automatically cause
> > > revalidation.
> > 
> > Which I seem to remember was a deliberate choice: some change
> > capacities occur because the path goes passive and default values get
> > installed.
> 
> Yep, it's very tricky territory.
> 

Yes, there are some storage arrays that refuse a READ CAPACITY
command in certain ALUA states so you can't get the new capacity anyway.

It might be nice to improve this, though, there are some cases now where
we set the capacity to zero when we revalidate and can't get the value.

-Ewan