PVE: add zero block handling to PBS dump callback

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

debian/patches/pve/0048-PVE-add-zero-block-handling-to-PBS-dump-callback.patch

@@ -0,0 +1,85 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Stefan Reiter <s.reiter@proxmox.com>
+Date: Thu, 13 Aug 2020 13:50:27 +0200
+Subject: [PATCH] PVE: add zero block handling to PBS dump callback
+
+Both the PBS and VMA dump callbacks assume that a NULL pointer can be
+passed as *pbuf, but that never happens, as backup-dump.c calls this
+function with contents of an iovec.
+
+So first, remove that assumption and add an 'assert' to verify.
+
+Secondly, while the vma-writer already does the buffer_is_zero check
+internally, for PBS we relied on that non-existant behaviour for zero
+chunks, so do the buffer_is_zero check manually and pass NULL to the
+rust lib in case it is true.
+
+Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
+---
+ pve-backup.c | 14 +++++++++-----
+ 1 file changed, 9 insertions(+), 5 deletions(-)
+
+diff --git a/pve-backup.c b/pve-backup.c
+index 40d8136f1a..7c99554514 100644
+--- a/pve-backup.c
++++ b/pve-backup.c
+@@ -8,6 +8,7 @@
+ #include "block/blockjob.h"
+ #include "qapi/qapi-commands-block.h"
+ #include "qapi/qmp/qerror.h"
++#include "qemu/cutils.h"
+ 
+ /* PVE backup state and related function */
+ 
+@@ -136,10 +137,13 @@ pvebackup_co_dump_pbs_cb(
+     PVEBackupDevInfo *di = opaque;
+ 
+     assert(backup_state.pbs);
++    assert(buf);
+ 
+     Error *local_err = NULL;
+     int pbs_res = -1;
+ 
++    bool is_zero_block = size == di->block_size && buffer_is_zero(buf, size);
++
+     qemu_co_mutex_lock(&backup_state.dump_callback_mutex);
+ 
+     // avoid deadlock if job is cancelled
+@@ -155,7 +159,8 @@ pvebackup_co_dump_pbs_cb(
+         uint64_t to_transfer = left < di->block_size ? left : di->block_size;
+ 
+         pbs_res = proxmox_backup_co_write_data(backup_state.pbs, di->dev_id,
+-            buf ? buf + transferred : NULL, start + transferred, to_transfer, &local_err);
++            is_zero_block ? NULL : buf + transferred, start + transferred,
++            to_transfer, &local_err);
+         transferred += to_transfer;
+ 
+         if (pbs_res < 0) {
+@@ -168,7 +173,7 @@ pvebackup_co_dump_pbs_cb(
+     }
+ 
+     qemu_co_mutex_unlock(&backup_state.dump_callback_mutex);
+-    pvebackup_add_transfered_bytes(size, !buf ? size : 0, reused);
++    pvebackup_add_transfered_bytes(size, is_zero_block ? size : 0, reused);
+ 
+     return size;
+ }
+@@ -190,6 +195,7 @@ pvebackup_co_dump_vma_cb(
+     int ret = -1;
+ 
+     assert(backup_state.vmaw);
++    assert(buf);
+ 
+     uint64_t remaining = size;
+ 
+@@ -216,9 +222,7 @@ pvebackup_co_dump_vma_cb(
+         qemu_co_mutex_unlock(&backup_state.dump_callback_mutex);
+ 
+         ++cluster_num;
+-        if (buf) {
+-            buf += VMA_CLUSTER_SIZE;
+-        }
++        buf += VMA_CLUSTER_SIZE;
+         if (ret < 0) {
+             Error *local_err = NULL;
+             vma_writer_error_propagate(backup_state.vmaw, &local_err);

debian/patches/series

@@ -47,3 +47,4 @@ pve/0044-PVE-Add-PBS-block-driver-to-map-backup-archives-into.patch
 pve/0045-PVE-add-query_proxmox_support-QMP-command.patch
 pve/0046-pbs-fix-missing-crypt-and-compress-parameters.patch
 pve/0047-pbs-handle-write-callback-with-big-blocks-correctly.patch
+pve/0048-PVE-add-zero-block-handling-to-PBS-dump-callback.patch