generic/35[67]: disable swapfile tests on Btrfs

Btrfs doesn't support swapfiles (yet?), so generic/356 fails
erroneously, and generic/357 only passes by accident. Let's add a
_require_scratch_swapfile helper and add it to these tests.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

common/rc

@@ -1790,6 +1790,28 @@ _require_odirect()
 	rm -f $testfile 2>&1 > /dev/null
 }
 
+# Check that the filesystem supports swapfiles
+_require_scratch_swapfile()
+{
+	_require_scratch
+
+	_scratch_mkfs >/dev/null
+	_scratch_mount
+
+	# Minimum size for mkswap is 10 pages
+	local size=$(($(get_page_size) * 10))
+
+	_pwrite_byte 0x61 0 "$size" "$SCRATCH_MNT/swap" >/dev/null 2>&1
+	mkswap "$SCRATCH_MNT/swap" >/dev/null 2>&1
+	if ! swapon "$SCRATCH_MNT/swap" >/dev/null 2>&1; then
+		_scratch_unmount
+		_notrun "swapfiles are not supported"
+	fi
+
+	swapoff "$SCRATCH_MNT/swap" >/dev/null 2>&1
+	_scratch_unmount
+}
+
 # Check that a fs has enough free space (in 1024b blocks)
 #
 _require_fs_space()

tests/generic/356

@@ -44,6 +44,7 @@ _cleanup()
 
 # real QA test starts here
 _supported_os Linux
+_require_scratch_swapfile
 _require_scratch_reflink
 _require_cp_reflink
 

tests/generic/357

@@ -44,6 +44,7 @@ _cleanup()
 
 # real QA test starts here
 _supported_os Linux
+_require_scratch_swapfile
 _require_scratch_reflink
 _require_cp_reflink