* Markus Armbruster <arm...@redhat.com> [2010-11-06 04:19]: > Ryan Harper <ry...@us.ibm.com> writes: > > > * Markus Armbruster <arm...@redhat.com> [2010-11-05 11:11]: > >> Ryan Harper <ry...@us.ibm.com> writes: > >> > >> > * Markus Armbruster <arm...@redhat.com> [2010-11-05 08:28]: > >> >> I'd be fine with any of these: > >> >> > >> >> 1. A new command "device_disconnet ID" (or similar name) to disconnect > >> >> device ID from any host parts. Nice touch: you don't have to know > >> >> about the device's host part(s) to disconnect it. But it might be > >> >> more work than the other two. > >> > > >> > This is sort of what netdev_del() and drive_unplug() are today; we're > >> > just saying sever the connection of this device id. > >> > >> No, I have netdev_del as (3). > >> > >> All three options are "sort of" the same, just different commands with > >> a common purpose. > >> > >> > I'd like to rename drive_unplug() to blockdev_del() and call it done. I > >> > was looking at libvirt and the right call to netdev_del is already > >> > in-place; I'd just need to re-spin my block patch to call blockdev_del() > >> > after invoking device_del() to match what is done for net. > >> > >> Unless I'm missing something, you can't just rename: your unplug does > >> not delete the host part. > >> > >> >> 2. New commands netdev_disconnect, drive_disconnect (or similar names) > >> >> to disconnect a host part from a guest device. Like (1), except you > >> >> have to point to the other end of the connection to cut it. > >> > > >> > What's the advantage here? We need an additional piece of info (host > >> > part) in addition to the device id? > >> > >> That's a disadvantage. > >> > >> Possible advantage: implementation could be slightly easier than (1), > >> because you don't have to find the host parts. > >> > >> >> 3. A new command "drive_del ID" similar to existing netdev_del. This is > >> >> (2) fused with delete. Conceptual wart: you can't disconnect and > >> >> keep the host part around. Moreover, delete is slightly dangerous, > >> >> because it renders any guest device still using the host part > >> >> useless. > >> > > >> > Hrm, I thought that's what (1) is. > >> > >> No. > >> > >> With (1), the argument is a *device* ID, and we disconnect *all* host > >> parts connected to this device (typically just one). > >> > >> With (3), the argument is a netdev/drive ID, and disconnect *this* host > >> part from the peer device. > >> > >> > Well, either (1) or (3); I'd like to > >> > rename drive_unplug() to blockdev_del() since they're similar function > >> > w.r.t removing access to the host resource. And we can invoke them in > >> > the same way from libvirt (after doing guest notification, remove > >> > access). > >> > >> I'd call it drive_del for now, to match drive_add. > > > > OK, drive_del() and as you mentioned, drive_unplug will take out the > > block driver, but doesn't remove the dinfo object; that ends up dying > > when we call the device destructor. I think for symmetry we'll want > > drive_del to remove the dinfo object as well. > > Exactly. > > a. bdrv_detach() to zap the pointer from bdrv to qdev > b. zap the pointer from qdev to bdrv > c. drive_uninit() to dispose of the host part
a-c need to be done to match netdev_del symmetry? How hard of a req is this? > > Step b could be awkward with (3), because you don't know device details. > I guess you have to search device properties for a drive property > pointing to bdrv. I like (1) because it puts that loop in the one place > where it belongs: qdev core. (3) duplicates it in every HOSTDEV_del. > Except for netdev_del, which is special because of VLANs. > > To avoid step b, you could try to keep the bdrv around in a special > zombie state. Still have to free the dinfo, but can't use > drive_uninit() for that then. > > If you think I'm overcomplicating this, feel free to prove me wrong with > working code :) drive_unplug() works as-is today; so it does feel very combursome at this point. Other than the name change and agreement on how mgmt should invoke the command, it's been a long ride to get here. I'll take my best shot at trying to clean up the other pointers and objects; though on one of my attempts when I took out the dinfo() object that didn't go so well; going to have to audit who uses dinfo and where and what they check before calling it to have a proper cleanup that doesn't remove the whole device altogether. -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ry...@us.ibm.com
