Snapshotting a paused VM left it in finish-migrate, where it stayed until the VM was restarted. Fix this by storing the run state instead and put it back, similar to migration_iteration_finish().
While working on that, I noticed some memory leaks and other issues, which I found by using sanitizer tools like ASAN and reading the code and docs. Changes since the RFC: * store the run state via runstate_get() and restore it instead of skipping the transition into finish-migrate (Thanks @Fiona) * refuse a snapshot while an incoming migration is pending, which migrate_prepare() already does, otherwise the restore aborts * fixed multiple memory leaks * fixed multiple discarded error messages * removed raw uses of allocators * folded the changes into the relevant debian/patches Future work: * Once SAVE_STATE_ERROR is set, no new snapshot can be started and savevm-start fails with "VM snapshot already started" until the VM is restarted. Resetting that state looks difficult and could introduce new bugs. A couple of people ran into this before, see [0] and [1]. It would definitely be nicer if a single failed snapshot did not block further snapshots until a VM restart. * TSAN flags a data race on snap_state.bs_pos. Probably simply fixed by using atomics. There might be some other issues in savevm-async, but I have to check this in more detail. Note that patch 9 touches the same lines as [2]. [0] https://forum.proxmox.com/threads/snapshot-creation-issue.176090/ [1] https://forum.proxmox.com/threads/snapshot-fails-to-cleanup-and-prevents-future-snapshots.144757/ [2] https://lore.proxmox.com/all/[email protected]/ Erik Fastermann (9): d/patches: normalize header of pbs-restore no-cache patch pbs-restore: keep callback data on the stack migration/qemu-file: allocate buffer with g_malloc migration/pbs-state: check allocation of incoming state buffer savevm-async: drop QIOChannel reference savevm-async: free migration vmdesc savevm-async: release resources on start failure path savevm-async: include reason when file open fails savevm-async: restore run state from before snapshot ...async-for-background-state-snapshots.patch | 111 +++++++++++++----- ...add-optional-buffer-size-to-QEMUFile.patch | 29 ++--- ...estore-new-command-to-restore-from-p.patch | 16 +-- ...igrate-dirty-bitmap-state-via-savevm.patch | 25 ++-- ...se-migration-blocker-check-for-snaps.patch | 4 +- ...no-cache-flag-to-skip-host-page-cach.patch | 7 +- 6 files changed, 129 insertions(+), 63 deletions(-) -- 2.47.3
