[PATCH proxmox-backup 10/10] fix #7254: datastore: refuse new backps when capacity is almost full

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

Add a datastore config option that can be used to reserve free space.

HumanByte is somewhat inaccurate (e.g. 1025 MiB rounds to 1024 MiB)
but it should be good enough for this case.

Setting this option is not backwards compatible as older versions of
the parser will not recognize it. For example, running something like
`proxmox-backup-manager datastore list` will fail with older binaries.

Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
---
 pbs-datastore/src/chunk_store.rs | 34 +++++++++++++++++++++++++-------
 pbs-datastore/src/datastore.rs   |  9 +++++++++
 src/api2/config/datastore.rs     |  2 ++
 www/Utils.js                     |  6 ++++++
 www/datastore/OptionView.js      | 10 ++++++++++
 5 files changed, 54 insertions(+), 7 deletions(-)

diff --git a/pbs-datastore/src/chunk_store.rs b/pbs-datastore/src/chunk_store.rs
index 6a9dfbcef..515f007d3 100644
--- a/pbs-datastore/src/chunk_store.rs
+++ b/pbs-datastore/src/chunk_store.rs
@@ -10,6 +10,7 @@ use tracing::{info, warn};
 
 use pbs_api_types::{DatastoreFSyncLevel, GarbageCollectionStatus};
 use pbs_config::BackupLockGuard;
+use proxmox_human_byte::HumanByte;
 use proxmox_io::ReadExt;
 use proxmox_s3_client::S3Client;
 use proxmox_sys::fs::{create_dir, create_path, file_type_from_file_stat, CreateOptions};
@@ -105,6 +106,7 @@ impl ChunkStore {
         uid: nix::unistd::Uid,
         gid: nix::unistd::Gid,
         sync_level: DatastoreFSyncLevel,
+        reserved_space: Option<HumanByte>,
     ) -> Result<Self, Error>
     where
         P: Into<PathBuf>,
@@ -159,7 +161,7 @@ impl ChunkStore {
             }
         }
 
-        Self::open(name, base, sync_level)
+        Self::open(name, base, sync_level, reserved_space)
     }
 
     fn lockfile_path<P: Into<PathBuf>>(base: P) -> PathBuf {
@@ -193,6 +195,7 @@ impl ChunkStore {
         name: &str,
         base: P,
         sync_level: DatastoreFSyncLevel,
+        reserved_space: Option<HumanByte>,
     ) -> Result<Self, Error> {
         let base: PathBuf = base.into();
 
@@ -209,10 +212,14 @@ impl ChunkStore {
             locker: Some(locker),
             mutex: Mutex::new(()),
             sync_level,
-            fs_limit: FileSystemLimit::new(None),
+            fs_limit: FileSystemLimit::new(reserved_space.map(|s| s.as_u64())),
         })
     }
 
+    pub(crate) fn set_reserved_space(&self, bytes: Option<HumanByte>) {
+        self.fs_limit.set_reserved_space(bytes.map(|s| s.as_u64()));
+    }
+
     fn touch_chunk_no_lock(&self, digest: &[u8; 32]) -> Result<(), Error> {
         // unwrap: only `None` in unit tests
         assert!(self.locker.is_some());
@@ -998,14 +1005,21 @@ fn test_chunk_store1() {
     let temp_dir = TempDir::new().unwrap();
     let path = temp_dir.path();
 
-    let chunk_store = ChunkStore::open("test", path, DatastoreFSyncLevel::None);
+    let chunk_store = ChunkStore::open("test", path, DatastoreFSyncLevel::None, None);
     assert!(chunk_store.is_err());
 
     let user = nix::unistd::User::from_uid(nix::unistd::Uid::current())
         .unwrap()
         .unwrap();
-    let chunk_store =
-        ChunkStore::create("test", path, user.uid, user.gid, DatastoreFSyncLevel::None).unwrap();
+    let chunk_store = ChunkStore::create(
+        "test",
+        path,
+        user.uid,
+        user.gid,
+        DatastoreFSyncLevel::None,
+        Some(1 << 20),
+    )
+    .unwrap();
 
     let (chunk, digest) = crate::data_blob::DataChunkBuilder::new(&[0u8, 1u8])
         .build()
@@ -1021,8 +1035,14 @@ fn test_chunk_store1() {
     let (exists, _) = chunk_store.insert_chunk(&chunk, &digest).unwrap();
     assert!(exists);
 
-    let chunk_store =
-        ChunkStore::create("test", path, user.uid, user.gid, DatastoreFSyncLevel::None);
+    let chunk_store = ChunkStore::create(
+        "test",
+        path,
+        user.uid,
+        user.gid,
+        DatastoreFSyncLevel::None,
+        None,
+    );
     assert!(chunk_store.is_err());
 
     temp_dir.close().unwrap();
diff --git a/pbs-datastore/src/datastore.rs b/pbs-datastore/src/datastore.rs
index def88f30a..46163f2bd 100644
--- a/pbs-datastore/src/datastore.rs
+++ b/pbs-datastore/src/datastore.rs
@@ -597,6 +597,13 @@ impl DataStore {
                     operation: Some(lookup.operation),
                 }));
             }
+            let tuning: DatastoreTuning = serde_json::from_value(
+                DatastoreTuning::API_SCHEMA
+                    .parse_property_string(config.tuning.as_deref().unwrap_or(""))?,
+            )?;
+            datastore
+                .chunk_store
+                .set_reserved_space(tuning.reserved_space);
             Arc::clone(&datastore.chunk_store)
         } else {
             let tuning: DatastoreTuning = serde_json::from_value(
@@ -607,6 +614,7 @@ impl DataStore {
                 lookup.name,
                 config.absolute_path(),
                 tuning.sync_level.unwrap_or_default(),
+                tuning.reserved_space,
             )?)
         };
 
@@ -699,6 +707,7 @@ impl DataStore {
             &name,
             config.absolute_path(),
             tuning.sync_level.unwrap_or_default(),
+            tuning.reserved_space,
         )?;
         let inner = Arc::new(Self::with_store_and_config(
             Arc::new(chunk_store),
diff --git a/src/api2/config/datastore.rs b/src/api2/config/datastore.rs
index 16e85a636..50019e8bd 100644
--- a/src/api2/config/datastore.rs
+++ b/src/api2/config/datastore.rs
@@ -170,6 +170,7 @@ pub(crate) fn do_create_datastore(
                 &datastore.name,
                 &path,
                 tuning.sync_level.unwrap_or_default(),
+                tuning.reserved_space,
             )
         })?
     } else {
@@ -207,6 +208,7 @@ pub(crate) fn do_create_datastore(
             backup_user.uid,
             backup_user.gid,
             tuning.sync_level.unwrap_or_default(),
+            tuning.reserved_space,
         )?
     };
 
diff --git a/www/Utils.js b/www/Utils.js
index a9239b005..ebb681bfa 100644
--- a/www/Utils.js
+++ b/www/Utils.js
@@ -909,6 +909,12 @@ Ext.define('PBS.Utils', {
         sync = PBS.Utils.tuningOptions['sync-level'][sync ?? '__default__'];
         options.push(`${gettext('Sync Level')}: ${sync}`);
 
+        let reserved_space = tuning['reserved-space'];
+        delete tuning['reserved-space'];
+        options.push(
+            `${gettext('Reserved Space')}: ${reserved_space ?? gettext('None')}`,
+        );
+
         let gc_atime_safety_check = tuning['gc-atime-safety-check'];
         delete tuning['gc-atime-safety-check'];
         options.push(
diff --git a/www/datastore/OptionView.js b/www/datastore/OptionView.js
index bac9eab0c..dbf12b99b 100644
--- a/www/datastore/OptionView.js
+++ b/www/datastore/OptionView.js
@@ -309,6 +309,16 @@ Ext.define('PBS.Datastore.Options', {
                             deleteEmpty: true,
                             value: '__default__',
                         },
+                        {
+                            xtype: 'pmxSizeField',
+                            name: 'reserved-space',
+                            fieldLabel: gettext('Reserved Space'),
+                            labelWidth: 200,
+                            unit: 'MiB',
+                            submitAutoScaledSizeUnit: true,
+                            allowZero: true,
+                            emptyText: gettext('None'),
+                        },
                         {
                             xtype: 'proxmoxcheckbox',
                             name: 'gc-atime-safety-check',
-- 
2.47.3