[PATCH manager v3] fix #4503: ui: qemu: add detect zeroes disk option

[Lukas Sichert <l.sichert@proxmox.com>]

When discard is enabled, qemu-server defaults to 'detect-zeroes=unmap'.
This can have a significant performance impact for zero writes on some
setups, while users might still want to keep guest discard/TRIM support
enabled.

Allow configuring the option independently so 'discard' can stay enabled
while zero detection is disabled. Persist the checkbox state explicitly,
as the backend treats an absent value as default-enabled behavior,
resulting in 'detect-zeroes=unmap' when 'discard' is enabled.

Link: https://bugzilla.proxmox.com/show_bug.cgi?id=4503
Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
---

Notes:
    changes from v2 to v3 (thanks @Fabian):
    - add a comment explaining why this property is handled differently from
      the others
    
    changes from v1 to v2:
    - added bug-numer to commit header
    - appended bug-link to commit body

 www/manager6/qemu/HDEdit.js | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/www/manager6/qemu/HDEdit.js b/www/manager6/qemu/HDEdit.js
index 1bb2bfda..2708d452 100644
--- a/www/manager6/qemu/HDEdit.js
+++ b/www/manager6/qemu/HDEdit.js
@@ -96,6 +96,9 @@ Ext.define('PVE.qemu.HDInputPanel', {
         PVE.Utils.propertyStringSet(me.drive, values.readOnly, 'ro', 'on');
         PVE.Utils.propertyStringSet(me.drive, values.cache, 'cache');
         PVE.Utils.propertyStringSet(me.drive, values.aio, 'aio');
+        // persist an explicit false value, since the backend defaults to enabled
+        // when the option is omitted.
+        me.drive.detect_zeroes = values.detect_zeroes ? 1 : 0;
 
         ['mbps_rd', 'mbps_wr', 'iops_rd', 'iops_wr'].forEach((name) => {
             let burst_name = `${name}_max`;
@@ -152,6 +155,7 @@ Ext.define('PVE.qemu.HDInputPanel', {
         values.diskformat = drive.format || 'raw';
         values.cache = drive.cache || '__default__';
         values.discard = drive.discard === 'on';
+        values.detect_zeroes = PVE.Parser.parseBoolean(drive.detect_zeroes, 1);
         values.ssd = PVE.Parser.parseBoolean(drive.ssd);
         values.iothread = PVE.Parser.parseBoolean(drive.iothread);
         values.readOnly = PVE.Parser.parseBoolean(drive.ro);
@@ -317,6 +321,12 @@ Ext.define('PVE.qemu.HDInputPanel', {
                 reference: 'discard',
                 name: 'discard',
             },
+            {
+                xtype: 'proxmoxcheckbox',
+                fieldLabel: gettext('Detect zeroes'),
+                reference: 'detect_zeroes',
+                name: 'detect_zeroes',
+            },
             {
                 xtype: 'proxmoxcheckbox',
                 name: 'iothread',
-- 
2.47.3