[PATCH] generic: add test for missing btrfs csums in log when doing async on subpage vol

[Mark Harmstone <maharmstone@fb.com>]

Adds a test for a bug we encountered on Linux 6.4 on aarch64, where a
race could mean that csums weren't getting written to the log tree,
leading to corruption when it was replayed.

The patches to detect log this tree corruption are in btrfs-progs 6.11.

Signed-off-by: Mark Harmstone <maharmstone@fb.com>
---
This is a genericized version of the test I originally proposed as
btrfs/333.

 tests/generic/757     | 71 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/757.out |  2 ++
 2 files changed, 73 insertions(+)
 create mode 100755 tests/generic/757
 create mode 100644 tests/generic/757.out

diff --git a/tests/generic/757 b/tests/generic/757
new file mode 100755
index 00000000..6ad3d01e
--- /dev/null
+++ b/tests/generic/757
@@ -0,0 +1,71 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# FS QA Test 757
+#
+# Test async dio with fsync to test a btrfs bug where a race meant that csums
+# weren't getting written to the log tree, causing corruptions on remount.
+# This can be seen on subpage FSes on Linux 6.4.
+#
+. ./common/preamble
+_begin_fstest auto quick metadata log recoveryloop
+
+_fixed_by_kernel_commit e917ff56c8e7 \
+	"btrfs: determine synchronous writers from bio or writeback control"
+
+fio_config=$tmp.fio
+
+. ./common/dmlogwrites
+
+_require_scratch
+_require_log_writes
+
+cat >$fio_config <<EOF
+[global]
+iodepth=128
+direct=1
+ioengine=libaio
+rw=randwrite
+runtime=1s
+[job0]
+rw=randwrite
+filename=$SCRATCH_MNT/file
+size=1g
+fdatasync=1
+EOF
+
+_require_fio $fio_config
+
+cat $fio_config >> $seqres.full
+
+_log_writes_init $SCRATCH_DEV
+_log_writes_mkfs >> $seqres.full 2>&1
+_log_writes_mark mkfs
+
+_log_writes_mount
+
+$FIO_PROG $fio_config > /dev/null 2>&1
+_log_writes_unmount
+
+_log_writes_remove
+
+prev=$(_log_writes_mark_to_entry_number mkfs)
+[ -z "$prev" ] && _fail "failed to locate entry mark 'mkfs'"
+cur=$(_log_writes_find_next_fua $prev)
+[ -z "$cur" ] && _fail "failed to locate next FUA write"
+
+while [ ! -z "$cur" ]; do
+	_log_writes_replay_log_range $cur $SCRATCH_DEV >> $seqres.full
+
+	_check_scratch_fs
+
+	prev=$cur
+	cur=$(_log_writes_find_next_fua $(($cur + 1)))
+	[ -z "$cur" ] && break
+done
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/757.out b/tests/generic/757.out
new file mode 100644
index 00000000..dfbc8094
--- /dev/null
+++ b/tests/generic/757.out
@@ -0,0 +1,2 @@
+QA output created by 757
+Silence is golden
-- 
2.44.2