| Message ID | m3oc69jruw.fsf@blackfin.pond.sub.org |
|---|---|
| State | New |
| Headers | show |
On Fri, Feb 18, 2011 at 5:16 PM, Markus Armbruster <armbru@redhat.com> wrote: > From 8cd4978c9be6ff2bcc414bb1c1b258b96b9a74c1 Mon Sep 17 00:00:00 2001 > From: Markus Armbruster <armbru@redhat.com> > Date: Fri, 18 Feb 2011 15:54:02 +0100 > > After forcefully ejecting media locked by the guest, you can't ever > again insert new media. > > Example: > > (qemu) info block > hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 > cd: type=cdrom removable=1 locked=1 file=x.iso ro=0 drv=raw encrypted=0 > (qemu) eject cd > Device 'cd' is locked > (qemu) eject -f cd > (qemu) info block > hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 > cd: type=cdrom removable=1 locked=1 [not inserted] > (qemu) change cd x.iso > Device 'cd' is locked > > Signed-off-by: Markus Armbruster <armbru@redhat.com> > --- > I'm not entirely sure this is the appropriate fix, and that's why > there's RFC in the subject. > > Both IDE and SCSI devices expose their drive's BlockDriverState member > locked to the guest via mode sense. > > What does real hardware do when I force-eject media (typically by > rummaging in that little hole with a paperclip)? Does it actively > notify the OS? Does mode sense change? No idea, but IIRC the drive is still usable after that, so locking the drive does not look correct. > A possible alternative fix is to make do_change_block() ignore > bdrv_is_locked() when inserting media into an empty drive. Then the meaning of locked would change, maybe eject_disabled would then describe the state better.
Sorry for my slow reply. Blue Swirl <blauwirbel@gmail.com> writes: > On Fri, Feb 18, 2011 at 5:16 PM, Markus Armbruster <armbru@redhat.com> wrote: >> From 8cd4978c9be6ff2bcc414bb1c1b258b96b9a74c1 Mon Sep 17 00:00:00 2001 >> From: Markus Armbruster <armbru@redhat.com> >> Date: Fri, 18 Feb 2011 15:54:02 +0100 >> >> After forcefully ejecting media locked by the guest, you can't ever >> again insert new media. >> >> Example: >> >> (qemu) info block >> hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 >> cd: type=cdrom removable=1 locked=1 file=x.iso ro=0 drv=raw encrypted=0 >> (qemu) eject cd >> Device 'cd' is locked >> (qemu) eject -f cd >> (qemu) info block >> hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 >> cd: type=cdrom removable=1 locked=1 [not inserted] >> (qemu) change cd x.iso >> Device 'cd' is locked >> >> Signed-off-by: Markus Armbruster <armbru@redhat.com> >> --- >> I'm not entirely sure this is the appropriate fix, and that's why >> there's RFC in the subject. >> >> Both IDE and SCSI devices expose their drive's BlockDriverState member >> locked to the guest via mode sense. >> >> What does real hardware do when I force-eject media (typically by >> rummaging in that little hole with a paperclip)? Does it actively >> notify the OS? Does mode sense change? > > No idea, but IIRC the drive is still usable after that, That's what I'd expect. If the OS recovers from losing the media, the drive should be fine. > so locking the > drive does not look correct. I'm not sure I get you here. >> A possible alternative fix is to make do_change_block() ignore >> bdrv_is_locked() when inserting media into an empty drive. > > Then the meaning of locked would change, maybe eject_disabled would > then describe the state better. I like the current meaning of BlockDriverState member locked just fine, it nicely mirrors the SCSI / ATAPI mode sense page bit. I'm worried about unwanted side effects of my change. For instance, what about this code in do_snapshot_blkdev(): flags = bs->open_flags; bdrv_close(bs); ret = bdrv_open(bs, filename, flags, drv); I'm afraid my change would make it screw up bs->locked. Jes?
On (Fri) 18 Feb 2011 [16:16:07], Markus Armbruster wrote: > From 8cd4978c9be6ff2bcc414bb1c1b258b96b9a74c1 Mon Sep 17 00:00:00 2001 > From: Markus Armbruster <armbru@redhat.com> > Date: Fri, 18 Feb 2011 15:54:02 +0100 > > After forcefully ejecting media locked by the guest, you can't ever > again insert new media. > > Example: > > (qemu) info block > hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 > cd: type=cdrom removable=1 locked=1 file=x.iso ro=0 drv=raw encrypted=0 > (qemu) eject cd > Device 'cd' is locked > (qemu) eject -f cd > (qemu) info block > hda: type=hd removable=0 file=test.img ro=0 drv=raw encrypted=0 > cd: type=cdrom removable=1 locked=1 [not inserted] > (qemu) change cd x.iso > Device 'cd' is locked > > Signed-off-by: Markus Armbruster <armbru@redhat.com> > --- > I'm not entirely sure this is the appropriate fix, and that's why > there's RFC in the subject. > > Both IDE and SCSI devices expose their drive's BlockDriverState member > locked to the guest via mode sense. > > What does real hardware do when I force-eject media (typically by > rummaging in that little hole with a paperclip)? Does it actively > notify the OS? Does mode sense change? I think this should happen. Calling the 'change_cb' with a new CHANGE_EJECT parameter can notify the guest of the medium going from READY to NO_MEDIUM. The guest can then probe for the status of the tray. However, I currently don't know if devices are supposed to send such events to OSes, and how, if they are supposed to. We currently approximate this using ide_set_irq() for the cdrom case in cdrom_change_cb(). This patch looks sensible, though. > A possible alternative fix is to make do_change_block() ignore > bdrv_is_locked() when inserting media into an empty drive. > > block.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/block.c b/block.c > index b476479..295cf7b 100644 > --- a/block.c > +++ b/block.c > @@ -682,6 +682,7 @@ void bdrv_close(BlockDriverState *bs) > } > > /* call the change callback */ > + bs->locked = 0; > bs->media_changed = 1; > if (bs->change_cb) > bs->change_cb(bs->change_opaque, CHANGE_MEDIA); Amit
diff --git a/block.c b/block.c index b476479..295cf7b 100644 --- a/block.c +++ b/block.c @@ -682,6 +682,7 @@ void bdrv_close(BlockDriverState *bs) } /* call the change callback */ + bs->locked = 0; bs->media_changed = 1; if (bs->change_cb) bs->change_cb(bs->change_opaque, CHANGE_MEDIA);