feat: implement revertable snapshot support with version validation

Add support for creating revert boot entries when snapm is available.
This allows users to boot into a special mode that automatically merges
snapshots back into their origin volumes for disaster recovery.

The revertable parameter now properly validates snapm availability and
version support, failing explicitly rather than being silently ignored.

Changes:
- Add SNAPM_REVERT_PARAM_MIN_VERSION constant (0.5.0)
- Add has_revert_parameter() version check function
- Implement revertable parameter handling with conflict detection
- Add explicit version validation for bootable and revertable features
- Fail with ERROR_REVERTABLE_NOT_SUPPORTED when snapm is unavailable
  or version doesn't support revert parameter
- Pass bootable/revert parameters to snapm create_snapshot_set via kwargs
  pattern for clean version-conditional support
- Propagate revertable parameter through validation layer
- Add ERROR_REVERTABLE_NOT_SUPPORTED and ERROR_REVERTABLE_CONFLICT
  status codes
- Add debug logging for create_snapshot_set calls

The implementation mirrors the existing bootable parameter handling,
supporting both global-level and snapset-level configuration with
conflict detection. Both parameters now validate properly instead of
silently ignoring unsupported features.

Signed-off-by: Todd Gill <tgill@redhat.com>

Author: trgill

module_utils/snapshot_lsr/consts.py

@@ -61,6 +61,8 @@ class SnapshotStatus:
     ERROR_SNAPM_INTERNAL_ERROR = 42
     ERROR_BOOTABLE_NOT_SUPPORTED = 43
     ERROR_BOOTABLE_CONFLICT = 44
+    ERROR_REVERTABLE_NOT_SUPPORTED = 45
+    ERROR_REVERTABLE_CONFLICT = 46
 
 
 COMMAND_ENV = {"LC_ALL": "C", "LVM_COMMAND_PROFILE": "lvmdbusd"}

module_utils/snapshot_lsr/lvm.py

@@ -1235,6 +1235,20 @@ def snapshot_set(module, snapset_json, check_mode):
             changed,
         )
 
+    # If this function has been called with revertable snapshot requested, return error
+    # because snapm is required for revertable snapshots.
+    if any(
+        (
+            snapset_json.get("snapshot_lvm_revertable", False),
+            snapset_json.get("revertable", False),
+        )
+    ):
+        return (
+            SnapshotStatus.ERROR_REVERTABLE_NOT_SUPPORTED,
+            "Revertable snapshots are not supported without snapm",
+            changed,
+        )
+
     rc, message = verify_snapset_source_lvs_exist(module, snapset_json)
     if rc != SnapshotStatus.SNAPSHOT_OK:
         return rc, message, changed

module_utils/snapshot_lsr/snapmgr.py

@@ -35,6 +35,9 @@
 # Minimum version of snapm that supports the boot parameter
 # in the create_snapshot_set function.
 SNAPM_BOOT_PARAM_MIN_VERSION = "0.4.3"
+# Minimum version of snapm that supports the revert parameter
+# in the create_snapshot_set function.
+SNAPM_REVERT_PARAM_MIN_VERSION = "0.5.0"
 
 
 # NOTE: Because of PEP632, we cannot use distutils.
@@ -73,6 +76,16 @@ def has_boot_parameter():
     return True
 
 
+def has_revert_parameter():
+
+    if not snapshot_manager_imported or lsr_parse_version(
+        snapm.__version__
+    ) < lsr_parse_version(SNAPM_REVERT_PARAM_MIN_VERSION):
+        return False
+
+    return True
+
+
 def mgr_get_snapshot_lv(module, origin_vg, origin_lv, snapshot_set):
 
     for snapshot in snapshot_set[0].snapshots:
@@ -202,6 +215,7 @@ def mgr_check_verify_lvs_set(manager, module, snapset_json):
 
 def mgr_snapshot_cmd(module, module_args, snapset_json):
     bootable = None
+    revertable = None
     snapset_name = snapset_json["name"]
     logger.info("mgr_snapshot_cmd: %s", snapset_name)
     changed = False
@@ -237,8 +251,48 @@ def mgr_snapshot_cmd(module, module_args, snapset_json):
                 "changed": False,
             }
 
+    # Revertable global variable is set
+    if module_args["snapshot_lvm_revertable"]:
+        revertable = module_args["snapshot_lvm_revertable"]
+
+    # Global is not set, check the snapset
+    if revertable is None:
+        if "revertable" in snapset_json:
+            revertable = snapset_json["revertable"]
+        else:
+            revertable = False
+    else:  # Global is set, check for conflict
+        if (
+            "revertable" in snapset_json
+            and snapset_json["revertable"] is not None
+            and revertable != snapset_json["revertable"]
+        ):
+            return {
+                "return_code": SnapshotStatus.ERROR_REVERTABLE_CONFLICT,
+                "errors": "Conflicting values for revertable",
+                "changed": False,
+            }
+
     source_list = mgr_get_source_list_for_create(volume_list)
 
+    # Check if bootable is requested but not supported by snapm version
+    if bootable and not has_boot_parameter():
+        return {
+            "return_code": SnapshotStatus.ERROR_BOOTABLE_NOT_SUPPORTED,
+            "errors": "Bootable snapshots require snapm version %s or later"
+            % SNAPM_BOOT_PARAM_MIN_VERSION,
+            "changed": False,
+        }
+
+    # Check if revertable is requested but not supported by snapm version
+    if revertable and not has_revert_parameter():
+        return {
+            "return_code": SnapshotStatus.ERROR_REVERTABLE_NOT_SUPPORTED,
+            "errors": "Revertable snapshots require snapm version %s or later"
+            % SNAPM_REVERT_PARAM_MIN_VERSION,
+            "changed": False,
+        }
+
     if check_mode:
         return {
             "return_code": SnapshotStatus.SNAPSHOT_OK,
@@ -249,19 +303,24 @@ def mgr_snapshot_cmd(module, module_args, snapset_json):
     manager = snap_manager.Manager()
 
     try:
+        # Build kwargs for create_snapshot_set based on available parameters
+        kwargs = {}
         if has_boot_parameter():
-            manager.create_snapshot_set(
-                snapset_name,
-                source_list,
-                SNAPM_DEFAULT_SIZE_POLICY,
-                boot=bootable,
-            )
-        else:
-            manager.create_snapshot_set(
-                snapset_name,
-                source_list,
-                SNAPM_DEFAULT_SIZE_POLICY,
-            )
+            kwargs["boot"] = bootable
+        if has_revert_parameter():
+            kwargs["revert"] = revertable
+
+        logger.info(
+            "DEBUG: Calling create_snapshot_set with snapset_name=%s, "
+            "source_list=%s, default_size_policy=%s, kwargs=%s",
+            snapset_name,
+            source_list,
+            SNAPM_DEFAULT_SIZE_POLICY,
+            kwargs,
+        )
+        manager.create_snapshot_set(
+            snapset_name, source_list, SNAPM_DEFAULT_SIZE_POLICY, **kwargs
+        )
         changed = True
     except snapm.SnapmError as snap_err:
         # if the set already exists, return ok

module_utils/snapshot_lsr/validate.py

@@ -36,6 +36,9 @@ def get_json_from_args(module, module_args, vg_include):
     if module_args["snapshot_lvm_bootable"]:
         args_dict["bootable"] = module_args["snapshot_lvm_bootable"]
 
+    if module_args["snapshot_lvm_revertable"]:
+        args_dict["revertable"] = module_args["snapshot_lvm_revertable"]
+
     for vg, lv_list in vgs_lvs_iterator(
         module,
         module_args["snapshot_lvm_vg"],
@@ -341,6 +344,9 @@ def validate_snapset_json(cmd, module_args, verify_only):
     if module_args["snapshot_lvm_bootable"]:
         snapset_dict["snapshot_lvm_bootable"] = module_args["snapshot_lvm_bootable"]
 
+    if module_args["snapshot_lvm_revertable"]:
+        snapset_dict["snapshot_lvm_revertable"] = module_args["snapshot_lvm_revertable"]
+
     if cmd == SnapshotCommand.SNAPSHOT:
         rc, message = validate_json_request(snapset_dict, True)
     elif cmd == SnapshotCommand.CHECK and not verify_only: