[PATCH] generic/639: Add tiny swapfile test

[Ritesh Harjani <riteshh@linux.ibm.com>]

This adds a swap test for tiny discontiguous swapfile.
This was causing a kernel crash on XFS with kernel <= v4.18 and could
cause a invalid huge swapfile to get registered on latest kernel which
may lead to random corruption later.
(This happens only on bs < ps configuration)

More details about the kernel issue could be found in commit msg of the
fix at [1].

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5808fecc572391867fcd929662b29c12e6d08d81

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
---
 tests/generic/639     | 78 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/639.out |  2 ++
 tests/generic/group   |  1 +
 3 files changed, 81 insertions(+)
 create mode 100755 tests/generic/639
 create mode 100644 tests/generic/639.out

diff --git a/tests/generic/639 b/tests/generic/639
new file mode 100755
index 00000000..3c6d8f1b
--- /dev/null
+++ b/tests/generic/639
@@ -0,0 +1,78 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 YOUR NAME HERE.  All Rights Reserved.
+#
+# FS QA Test 639
+#
+# Test tiny swapfile with discontiguity. This was causing a kernel crash on XFS
+# with kernel version <= v4.18. And/or could cause a invalid swapfilesize to get
+# registered, which could cause some corruption later in the running kernel.
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=0	# success is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_require_test
+_require_xfs_io_command "fcollapse"
+_require_test_program mkswap
+_require_test_program swapon
+_require_scratch_swapfile
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount >>$seqres.full 2>&1
+
+SWAPFILE=$SCRATCH_MNT/swapscratch-$seq
+PS=$(get_page_size)
+BS=$(_get_block_size $SCRATCH_MNT)
+
+if [ $BS -gt $(($PS / 4)) ]; then
+	_notrun "This test requires blocksize atleast less or equal to pagesize/4, bs=$BS, ps=$PS"
+fi
+
+# create a swapfile
+$XFS_IO_PROG -f -c "pwrite 0 $(($PS + $PS + $BS + $BS))" -c fsync $SWAPFILE >> $seqres.full
+$XFS_IO_PROG -c "fcollapse $(($PS - $BS)) $BS" $SWAPFILE >> $seqres.full
+$XFS_IO_PROG -c "fcollapse $(($PS*2 - $BS*2)) $BS" $SWAPFILE >> $seqres.full
+$CHATTR_PROG +C $SWAPFILE >> $seqres.full 2>&1
+"$here/src/mkswap" $SWAPFILE
+
+"$here/src/swapon" $SWAPFILE >> $seqres.full 2>&1
+ret=$?
+if [ $ret -eq 0 ]; then
+	swapsize_kb=$(cat /proc/swaps |grep $SWAPFILE |awk '{print $3}')
+	swapsize=$(($swapsize_kb * 1024))
+	filesize=$(_get_filesize $SWAPFILE)
+
+	# error case
+	if [ $swapsize -gt $filesize ]; then
+		status=1
+		echo "Allocated swap size($swapsize) cannot be greater than swapfile size($filesize)"
+	fi
+fi
+swapoff $SWAPFILE >> $seqres.full 2>&1
+
+echo "Silence is golden"
+exit
diff --git a/tests/generic/639.out b/tests/generic/639.out
new file mode 100644
index 00000000..62c66537
--- /dev/null
+++ b/tests/generic/639.out
@@ -0,0 +1,2 @@
+QA output created by 639
+Silence is golden
diff --git a/tests/generic/group b/tests/generic/group
index 9a636b23..48ffa3c7 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -641,3 +641,4 @@
 636 auto quick swap
 637 auto quick dir
 638 auto quick rw
+639 auto quick swap
-- 
2.31.1