Backport 1.12.0: check-weight: Disable total pov size check for mandatory extrinsics (paritytech#4592)

Backport of paritytech#4571

---------

Co-authored-by: command-bot <>

Author: skunert

prdoc/1.12.0/pr_4571.prdoc

@@ -0,0 +1,17 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Ignore mandatory extrinsics in total PoV size check
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      The `CheckWeight` extension is checking that extrinsic length and used storage proof
+      weight together do not exceed the PoV size limit. This lead to problems when
+      the PoV size was already reached before mandatory extrinsics were applied.The `CheckWeight`
+      extension will now allow extrinsics of `DispatchClass::Mandatory` to be applied even if
+      the limit is reached.
+
+crates:
+  - name: frame-system
+    bump: minor

substrate/frame/system/src/extensions/check_weight.rs

@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::{limits::BlockWeights, Config, Pallet, LOG_TARGET};
+use crate::{limits::BlockWeights, Config, DispatchClass, Pallet, LOG_TARGET};
 use codec::{Decode, Encode};
 use frame_support::{
 	dispatch::{DispatchInfo, PostDispatchInfo},
@@ -822,6 +822,12 @@ mod tests {
 			consumed.total().saturating_sub(all_weight.total()),
 			normal.weight.add_proof_size(100)
 		);
+		assert_ok!(check_combined_proof_size::<<Test as Config>::RuntimeCall>(
+			&mandatory,
+			&maximum_weight,
+			6,
+			&next_weight
+		));
 
 		let consumed = calculate_consumed_weight::<<Test as Config>::RuntimeCall>(
 			&maximum_weight,
@@ -835,6 +841,12 @@ mod tests {
 			consumed.total().saturating_sub(all_weight.total()),
 			mandatory.weight.add_proof_size(100)
 		);
+		assert_ok!(check_combined_proof_size::<<Test as Config>::RuntimeCall>(
+			&mandatory,
+			&maximum_weight,
+			1,
+			&next_weight
+		));
 
 		// Using oversized zero length extrinsics.
 		let consumed = calculate_consumed_weight::<<Test as Config>::RuntimeCall>(