ran into this when live-restoring a backup configured for IO-threads,
got the good ol':
> qemu: qemu_mutex_unlock_impl: Operation not permitted
error.
Checking out the history of the related bdrv_backup_top_drop(*bs)
method, we can see that it used to do the AIO context acquiring too,
but in the backup path this was problematic and was changed to be
higher up in the call path in a upstream series from Stefan[0].
That said, this is a completely different code path and it is safe to
do so here. We always run from the main threads's AIO context here
and we call it only indirectly once, guarded by checking for
`s->drop_state == DropNone` and set `s->drop_state = DropRequested`
shortly before we schedule the track_drop() in a bh.
[0]: https://lists.gnu.org/archive/html/qemu-devel/2020-03/msg09139.html
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reads just nicer with a drain begin *and* end call. Also clearing the
backing link of the alloc track BDS makes it closer to
bdrv_backup_top_drop() with which this driver has a bit in common.
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
See added patches for more info, overview:
0044: slightly increase PBS performance by reducing allocations
0045: slightly increase block-stream performance for Ceph
0046: don't crash with block-stream on RBD
0047: add alloc-track driver for live restore
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
