generic: enable swapfile tests on Btrfs

Commit 8c96cfb ("generic/35[67]: disable swapfile tests on
Btrfs") disabled the swapfile tests on Btrfs because it did not
support swapfiles at the time. Now that we're adding support, we
want these tests to run, but they don't. _require_scratch_swapfile
always fails for Btrfs because swapfiles on Btrfs must be set to
nocow. After fixing that, generic/356 and generic/357 fail for the
same reason. After fixing _that_, both tests still fail because we
don't allow reflinking a non-checksummed extent (which nocow
implies) to a checksummed extent.

Add a helper for formatting a swap file which does the chattr, and
chattr the second file, which gets these tests running on kernels
supporting Btrfs swapfiles.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/rc

@@ -2225,6 +2225,19 @@ _require_odirect()
 	rm -f $testfile 2>&1 > /dev/null
 }
 
+_format_swapfile() {
+	local fname="$1"
+	local sz="$2"
+
+	rm -f "$fname"
+	touch "$fname"
+	chmod 0600 "$fname"
+	# Swap files must be nocow on Btrfs.
+	$CHATTR_PROG +C "$fname" > /dev/null 2>&1
+	_pwrite_byte 0x61 0 "$sz" "$fname" >> $seqres.full
+	mkswap "$fname" >> $seqres.full
+}
+
 # Check that the filesystem supports swapfiles
 _require_scratch_swapfile()
 {
@@ -2234,10 +2247,8 @@ _require_scratch_swapfile()
 	_scratch_mount
 
 	# Minimum size for mkswap is 10 pages
-	local size=$(($(get_page_size) * 10))
+	_format_swapfile "$SCRATCH_MNT/swap" $(($(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"

tests/generic/356

@@ -59,11 +59,12 @@ blocks=160
 blksz=65536
 
 echo "Initialize file"
-echo >> $seqres.full
-_pwrite_byte 0x61 0 $((blocks * blksz)) $testdir/file1 >> $seqres.full
-mkswap -U 27376b42-ff65-42ca-919f-6c9b62292a5c $testdir/file1 >> $seqres.full
+_format_swapfile "$testdir/file1" $((blocks * blksz))
 swapon $testdir/file1
 
+touch "$testdir/file2"
+$CHATTR_PROG +C "$testdir/file2" >/dev/null 2>&1
+
 echo "Try to reflink"
 _cp_reflink $testdir/file1 $testdir/file2 2>&1 | _filter_scratch
 

tests/generic/357

@@ -59,9 +59,9 @@ blocks=160
 blksz=65536
 
 echo "Initialize file"
-echo >> $seqres.full
-_pwrite_byte 0x61 0 $((blocks * blksz)) $testdir/file1 >> $seqres.full
-mkswap -U 27376b42-ff65-42ca-919f-6c9b62292a5c $testdir/file1 >> $seqres.full
+_format_swapfile "$testdir/file1" $((blocks * blksz))
+touch "$testdir/file2"
+$CHATTR_PROG +C "$testdir/file2" >/dev/null 2>&1
 _cp_reflink $testdir/file1 $testdir/file2 2>&1 | _filter_scratch
 
 echo "Try to swapon"