iotests: Provide a function for checking the creation of huge files

Some tests create huge (but sparse) files, and to be able to run those
tests in certain limited environments (like CI containers), we have to
check for the possibility to create such files first. Thus let's introduce
a common function to check for large files, and replace the already
existing checks in the iotests 005 and 220 with this function.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/005

@@ -59,10 +59,7 @@ fi
 # Sanity check: For raw, we require a file system that permits the creation
 # of a HUGE (but very sparse) file. Check we can create it before continuing.
 if [ "$IMGFMT" = "raw" ]; then
-    if ! truncate --size=5T "$TEST_IMG"; then
-        _notrun "file system on $TEST_DIR does not support large enough files"
-    fi
-    rm "$TEST_IMG"
+    _require_large_file 5T
 fi
 
 echo

tests/qemu-iotests/220

@@ -42,10 +42,8 @@ echo "== Creating huge file =="
 
 # Sanity check: We require a file system that permits the creation
 # of a HUGE (but very sparse) file.  tmpfs works, ext4 does not.
-if ! truncate --size=513T "$TEST_IMG"; then
-    _notrun "file system on $TEST_DIR does not support large enough files"
-fi
-rm "$TEST_IMG"
+_require_large_file 513T
+
 IMGOPTS='cluster_size=2M,refcount_bits=1' _make_test_img 513T
 
 echo "== Populating refcounts =="

tests/qemu-iotests/common.rc

@@ -643,5 +643,15 @@ _require_drivers()
     done
 }
 
+# Check that we have a file system that allows huge (but very sparse) files
+#
+_require_large_file()
+{
+    if ! truncate --size="$1" "$TEST_IMG"; then
+        _notrun "file system on $TEST_DIR does not support large enough files"
+    fi
+    rm "$TEST_IMG"
+}
+
 # make sure this script returns success
 true