On 2/12/19 9:03 AM, Christoph Hellwig wrote:
On Fri, Feb 08, 2019 at 06:38:31PM -0500, Martin K. Petersen wrote:
Some devices come online in write protected state and switch to
read-write once they are ready to process I/O requests.
That is really weird. What kind of devices are these?
No, not really.
Some arrays (HP IIRC) use a similar mechanism for volume copy or snapshots.
Note that per-partition ro settings are lost on revalidate. This has
been broken for at least a decade and it will require major surgery to
fix. To my knowledge nobody has complained about being unable to make
partition read-only settings stick through a revalidate. So hopefully
this patch will suffice as a simple fix for stable.
Should we warn when we lost these settings on a revalidate?
I have to say I don't like the tristate too much - it seems to allow
setting a hardware write protected device writable again by user
interfaction, right?
Should we just have a hardware and a user policy field that are separate
instead?
Problem is how the mechanism should work.
Thing is, once a device goes read-only we pretty much stop accessing it
(as it will send any filesystem down onto the recovery path).
And once we stop sending I/O to it we'll lose the ability to figure out
that the device switched back to R/W mode.
(Always assuming that we'll be getting a sense code in the first place).
But overall I have to agree with Christoph.
Read-only devices and the handling of which is pretty much
array-specific, so I doubt we can generalize much here.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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