Tests: cover uneven reads with 32 workers

Add a 33 sector range to the volume read test and correct the header compatibility check description in the big endian workflow.

.github/workflows/build-linux-big-endian.yml

@@ -2,7 +2,7 @@ name: Build and test Linux big-endian
 
 # Cross-builds the console version for s390x (big-endian) and runs it under
 # qemu-user: the algorithm self-tests, a read of known data from one of the
-# Tests/*.hc volumes without mounting, and a mount of one of them (all
+# Tests/*.hc volumes without mounting, and a header compatibility check (all
 # created on little-endian).
 #
 # The full suite (manual run with "full" selected) also builds amd64, then

Tests/volume_read_test.cpp

@@ -60,6 +60,7 @@ static void CheckRanges (Volume &volume, const SecureBuffer &data, const char *m
 	const uint64 sectors = data.Size() / sectorSize;
 	Require (sectors >= 34, "data area too small for the range checks");
 	const uint64 ranges[][2] = {
+		{ 1, 33 }, // Exercise uneven work distribution with 32 workers.
 		{ 1, 3 }, { 7, 5 }, { sectors / 2 - 4, 9 }, { sectors - 17, 17 }
 	};