On 2019-01-16 5:58 a.m., Martin Wilck wrote:
On Wed, 2019-01-16 at 11:32 +0100, Hannes Reinecke wrote:
On 1/16/19 11:26 AM, Martin Wilck wrote:
On Wed, 2019-01-16 at 08:35 +0100, Hannes Reinecke wrote:
If the device is _not_ removable we should not start the event
poller as the media will not go away. Having the event poller
running
will block the open() call as it will try to flush outstanding
events,
which it can't if the device is in state 'BLOCKED'. So the open()
call
will be stalled until the device state changed, which might be
quite
some time depending on the transport.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
---
drivers/scsi/sd.c | 3 +++
1 file changed, 3 insertions(+)
Thanks - you lost patience with me, did you? :-)
I didn't submit this yet because Tejun (adding him to CC) had
explicitly removed this check in commit 2bae0093cab4, and I was
still
trying to understand why.
Perhaps a follow-up discussion will clarify that.
To my understanding Tejun removed it as the check got moved into
set_media_not_present() function.
Maybe, but as a matter of fact, after 2bae0093cab4, TUR could be
executed for non-removable disks in sd_check_events(), which was never
done in sd_media_changed() beforehand.
However, I'd be very much interested to hear on how a non-removable
device can change ...
Me too. The specs at least don't seem to mandate that only removable
devices can return MEDIUM NOT PRESENT. But even then, it makes only
little sense to actively test such devices for a media change by
sending TURs.
So to be more precise, do you mean the LU disappearing while its
port(s) and containing target device remain online?
Otherwise a hot unplug meets the bill. Also some curious things can
happen at the transport level. For example I believe T10 have just
accepted a MODE SELECT command that will change a SAS wide port
to narrow port(s) (and vice versa). The device is taken offline for
a programmable period meant to be long enough for the scanning logic
to notice and then brought back in its new configuration.
Doug Gilbert
Sure, there might be non-compatible devices which do _not_ set the
removable flag (despite them being removable) and the notorious
aacraid
which insists on claiming all devices being removable, but if the
need
arises we can always introduce a blacklist flag.
I agree. Also, I suppose that if someone has a case for checking
for media change on non-removable devices, (s)he will bring it up.
Therefore:
Acked-by: Martin Wilck <mwilck@xxxxxxxx>
Regards
Martin
