[pve-devel] [PATCH pve-qemu] pbs-restore: unref/close target block backend

[Stefan Reiter]

Use blk_unref to drop the last reference, which will close the block
backend and flush all caches and outstanding writes.

This is especially important for restoring to Ceph, as the userspace
librbd caches will not be flushed if the application exits immediately,
leading to potentially incomplete restores.

Reported-by: Eneko Lacunza <elacunza at binovo.es>
Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
---

I was now able to reproduce the issue on Ceph, and this successfully fixes it
for me. Hash sums of before and after the restore now match up.

Without this, the difference in restored images would manifest in the broken one
simply missing some data at the back, instead just having zeroes there. This
might also be why it's not too noticeable usually - most data would be stored in
the earlier parts of the image, which always had enough time to be flushed.

This also brings it more in line with the code in vma.c, though we do a
bdrv_close_all there too - I did not find that to be necessary here, as
blk_unref already closes all attached block driver instances.

 ...ackup-pbs-restore-new-command-to-restore-from-p.patch | 9 +++++----
 debian/patches/pve/0039-PVE-fixup-pbs-restore-API.patch  | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/debian/patches/pve/0029-PVE-Backup-pbs-restore-new-command-to-restore-from-p.patch b/debian/patches/pve/0029-PVE-Backup-pbs-restore-new-command-to-restore-from-p.patch
index d7b0f39..2b04e1f 100644
--- a/debian/patches/pve/0029-PVE-Backup-pbs-restore-new-command-to-restore-from-p.patch
+++ b/debian/patches/pve/0029-PVE-Backup-pbs-restore-new-command-to-restore-from-p.patch
@@ -7,8 +7,8 @@ Subject: [PATCH] PVE-Backup: pbs-restore - new command to restore from proxmox
 Signed-off-by: Thomas Lamprecht <t.lamprecht at proxmox.com>
 ---
  meson.build   |   4 +
- pbs-restore.c | 217 ++++++++++++++++++++++++++++++++++++++++++++++++++
- 2 files changed, 221 insertions(+)
+ pbs-restore.c | 218 ++++++++++++++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 222 insertions(+)
  create mode 100644 pbs-restore.c
 
 diff --git a/meson.build b/meson.build
@@ -28,10 +28,10 @@ index 3094f98c47..6f1fafee14 100644
    subdir('contrib/elf2dmp')
 diff --git a/pbs-restore.c b/pbs-restore.c
 new file mode 100644
-index 0000000000..4bf37ef1fa
+index 0000000000..d4daee7e91
 --- /dev/null
 +++ b/pbs-restore.c
-@@ -0,0 +1,217 @@
+@@ -0,0 +1,218 @@
 +/*
 + * Qemu image restore helper for Proxmox Backup
 + *
@@ -241,6 +241,7 @@ index 0000000000..4bf37ef1fa
 +        verbose);
 +
 +    proxmox_restore_disconnect(conn);
++    blk_unref(blk);
 +
 +    if (res < 0) {
 +        fprintf(stderr, "restore failed: %s\n", pbs_error);
diff --git a/debian/patches/pve/0039-PVE-fixup-pbs-restore-API.patch b/debian/patches/pve/0039-PVE-fixup-pbs-restore-API.patch
index c5199e0..cc8f30a 100644
--- a/debian/patches/pve/0039-PVE-fixup-pbs-restore-API.patch
+++ b/debian/patches/pve/0039-PVE-fixup-pbs-restore-API.patch
@@ -9,7 +9,7 @@ Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
  1 file changed, 8 insertions(+), 2 deletions(-)
 
 diff --git a/pbs-restore.c b/pbs-restore.c
-index 4bf37ef1fa..ff3fc38e8a 100644
+index d4daee7e91..4d3f925a1b 100644
 --- a/pbs-restore.c
 +++ b/pbs-restore.c
 @@ -161,13 +161,19 @@ int main(int argc, char **argv)
-- 
2.20.1