[PATCH 1/2] xfs: make sure syncfs(2) passes back super_operations.sync_fs errors

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

This is a regression test to make sure that nonzero error returns from
a filesystem's ->sync_fs implementation are actually passed back to
userspace when the call stack involves syncfs(2).

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 tests/xfs/839     |   42 ++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/839.out |    2 ++
 2 files changed, 44 insertions(+)
 create mode 100755 tests/xfs/839
 create mode 100644 tests/xfs/839.out


diff --git a/tests/xfs/839 b/tests/xfs/839
new file mode 100755
index 00000000..9bfe93ef
--- /dev/null
+++ b/tests/xfs/839
@@ -0,0 +1,42 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 Oracle.  All Rights Reserved.
+#
+# FS QA Test No. 839
+#
+# Regression test for kernel commits:
+#
+# 5679897eb104 ("vfs: make sync_filesystem return errors from ->sync_fs")
+# 2d86293c7075 ("xfs: return errors in xfs_fs_sync_fs")
+#
+# During a code inspection, I noticed that sync_filesystem ignores the return
+# value of the ->sync_fs calls that it makes.  sync_filesystem, in turn is used
+# by the syncfs(2) syscall to persist filesystem changes to disk.  This means
+# that syncfs(2) does not capture internal filesystem errors that are neither
+# visible from the block device (e.g. media error) nor recorded in s_wb_err.
+# XFS historically returned 0 from ->sync_fs even if there were log failures,
+# so that had to be corrected as well.
+#
+# The kernel commits above fix this problem, so this test tries to trigger the
+# bug by using the shutdown ioctl on a clean, freshly mounted filesystem in the
+# hope that the EIO generated as a result of the filesystem being shut down is
+# only visible via ->sync_fs.
+#
+. ./common/preamble
+_begin_fstest auto quick shutdown
+
+# real QA test starts here
+
+# Modify as appropriate.
+_require_xfs_io_command syncfs
+_require_scratch_nocheck
+_require_scratch_shutdown
+
+# Reuse the fs formatted when we checked for the shutdown ioctl, and don't
+# bother checking the filesystem afterwards since we never wrote anything.
+_scratch_mount
+$XFS_IO_PROG -x -c 'shutdown -f ' -c syncfs $SCRATCH_MNT
+
+# success, all done
+status=0
+exit
diff --git a/tests/xfs/839.out b/tests/xfs/839.out
new file mode 100644
index 00000000..f275cdcc
--- /dev/null
+++ b/tests/xfs/839.out
@@ -0,0 +1,2 @@
+QA output created by 839
+syncfs: Input/output error