[PATCH] btrfs: add test for cases when a dio write has to fallback to a buffered write

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

Test cases where a direct IO write, with O_DSYNC, can not be done and has
to fallback to a buffered write.

This is motivated by a regression that was introduced in kernel 5.10 by
commit 0eb79294dbe328 ("btrfs: dio iomap DSYNC workaround")) and was
fixed in kernel 5.11 by commit ecfdc08b8cc65d ("btrfs: remove dio iomap
DSYNC workaround").

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 tests/btrfs/231     | 61 +++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/231.out | 21 ++++++++++++++++
 tests/btrfs/group   |  1 +
 3 files changed, 83 insertions(+)
 create mode 100755 tests/btrfs/231
 create mode 100644 tests/btrfs/231.out

diff --git a/tests/btrfs/231 b/tests/btrfs/231
new file mode 100755
index 00000000..9a404f57
--- /dev/null
+++ b/tests/btrfs/231
@@ -0,0 +1,61 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test No. btrfs/231
+#
+# Test cases where a direct IO write, with O_DSYNC, can not be done and has to
+# fallback to a buffered write.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+tmp=/tmp/$$
+status=1	# failure 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
+. ./common/attr
+
+# real QA test starts here
+_supported_fs btrfs
+_require_scratch
+_require_odirect
+_require_chattr c
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+# First lets test with an attempt to write into a file range with compressed
+# extents.
+touch $SCRATCH_MNT/foo
+$CHATTR_PROG +c $SCRATCH_MNT/foo
+
+$XFS_IO_PROG -s -c "pwrite -S 0xab -b 1M 0 1M" $SCRATCH_MNT/foo | _filter_xfs_io
+# Now do the direct IO write...
+$XFS_IO_PROG -d -s -c "pwrite -S 0xcd 512K 512K" $SCRATCH_MNT/foo | _filter_xfs_io
+
+# Now try doing a write into an unaligned offset...
+$XFS_IO_PROG -f -d -s -c "pwrite -S 0xef 1111 512K" $SCRATCH_MNT/bar | _filter_xfs_io
+
+# Unmount, mount again, and verify we have the expected data.
+_scratch_cycle_mount
+
+echo "File foo data:"
+od -A d -t x1 $SCRATCH_MNT/foo
+echo "File bar data:"
+od -A d -t x1 $SCRATCH_MNT/bar
+
+status=0
+exit
diff --git a/tests/btrfs/231.out b/tests/btrfs/231.out
new file mode 100644
index 00000000..def05769
--- /dev/null
+++ b/tests/btrfs/231.out
@@ -0,0 +1,21 @@
+QA output created by 231
+wrote 1048576/1048576 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 524288/524288 bytes at offset 524288
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 524288/524288 bytes at offset 1111
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+File foo data:
+0000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab
+*
+0524288 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd
+*
+1048576
+File bar data:
+0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+*
+0001104 00 00 00 00 00 00 00 ef ef ef ef ef ef ef ef ef
+0001120 ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef ef
+*
+0525392 ef ef ef ef ef ef ef
+0525399
diff --git a/tests/btrfs/group b/tests/btrfs/group
index a7c65983..9f63db69 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -233,3 +233,4 @@
 228 auto quick volume
 229 auto quick send clone
 230 auto quick qgroup limit
+231 auto quick compress rw
-- 
2.28.0