[PATCH proxmox-backup 4/6] task tracking: count WriteNonExpanding datastore operations

[Robert Obkircher <r.obkircher@proxmox.com>]

Count WriteNonExpanding as writes to ensure that switching over from
Write does not break forward compatibility when older versions read
the counters.

Also add a new counter to display the GarbageCollection maintenance
mode conflicts. It may not be accurate while older processes are
running but it should be good enough for the UI.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 pbs-datastore/src/task_tracking.rs | 12 ++++++++++++
 src/api2/admin/datastore.rs        |  1 +
 2 files changed, 13 insertions(+)

diff --git a/pbs-datastore/src/task_tracking.rs b/pbs-datastore/src/task_tracking.rs
index a67b77221..87ce4f5de 100644
--- a/pbs-datastore/src/task_tracking.rs
+++ b/pbs-datastore/src/task_tracking.rs
@@ -13,6 +13,12 @@ use serde::{Deserialize, Serialize};
 pub struct ActiveOperationStats {
     pub read: i64,
     pub write: i64,
+    /// The number of writers that do not significantly increase disk usage.
+    ///
+    /// The count is unreliable because older processes without this field
+    /// will delete it on every update!
+    #[serde(default)]
+    pub write_non_expanding: i64,
 }
 
 impl ActiveOperationStats {
@@ -20,6 +26,11 @@ impl ActiveOperationStats {
         match operation {
             Operation::Read => self.read += count,
             Operation::Write => self.write += count,
+            Operation::WriteNonExpanding => {
+                self.write += count;
+                // prevent underflow if an older process deleted the field
+                self.write_non_expanding = (self.write_non_expanding + count).max(0);
+            }
             Operation::Lookup => (), // no IO must happen there
         }
     }
@@ -33,6 +44,7 @@ impl Sum<Self> for ActiveOperationStats {
         iter.fold(Self::default(), |a, b| Self {
             read: a.read + b.read,
             write: a.write + b.write,
+            write_non_expanding: a.write_non_expanding + b.write_non_expanding,
         })
     }
 }
diff --git a/src/api2/admin/datastore.rs b/src/api2/admin/datastore.rs
index 94272c32d..3cbdd8922 100644
--- a/src/api2/admin/datastore.rs
+++ b/src/api2/admin/datastore.rs
@@ -2024,6 +2024,7 @@ pub fn get_active_operations(store: String, _param: Value) -> Result<Value, Erro
     Ok(json!({
         "read": active_operations.read,
         "write": active_operations.write,
+        "writeNonExpanding": active_operations.write_non_expanding,
     }))
 }
 
-- 
2.47.3