[PATCH v2 2/2] overlay: add test for rename of lower symlink with NOATIME attr

[Amir Goldstein <amir73il@gmail.com>]

Test for a regression in copy up of symlink that has the S_NOATIME
inode flag.

This is a regression from v5.15 reported by Ruiwen Zhao:
https://lore.kernel.org/linux-unionfs/CAKd=y5Hpg7J2gxrFT02F94o=FM9QvGp=kcH1Grctx8HzFYvpiA@mail.gmail.com/

In the bug report, the symlink has the S_NOATIME inode flag because it is
on an NFS/FUSE filesystem that sets S_NOATIME for all inodes.

The reproducer uses another technique to create a symlink with
S_NOATIME inode flag by using chattr +A inheritance on filesystems
that inherit chattr flags to symlinks.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 tests/overlay/082     | 66 +++++++++++++++++++++++++++++++++++++++++++
 tests/overlay/082.out |  2 ++
 2 files changed, 68 insertions(+)
 create mode 100755 tests/overlay/082
 create mode 100644 tests/overlay/082.out

diff --git a/tests/overlay/082 b/tests/overlay/082
new file mode 100755
index 00000000..97ef445e
--- /dev/null
+++ b/tests/overlay/082
@@ -0,0 +1,66 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2023 CTERA Networks. All Rights Reserved.
+#
+# FS QA Test 082
+#
+# Test for a regression in copy up of symlink that has the noatime inode
+# attribute.
+#
+# kernel commit 72db82115d2b ("ovl: copy up sync/noatime fileattr flags")
+# from v5.15 introduced the regression.
+#
+. ./common/preamble
+_begin_fstest auto quick copyup symlink atime
+
+# real QA test starts here
+_supported_fs overlay
+_fixed_by_kernel_commit ab048302026d \
+	"ovl: fix failed copyup of fileattr on a symlink"
+
+_require_scratch
+_require_chattr_inherit A
+
+# remove all files from previous runs
+_scratch_mkfs
+
+# prepare lower test dir with NOATIME flag
+lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+mkdir -p $lowerdir/testdir
+$CHATTR_PROG +A $lowerdir/testdir >> $seqres.full 2>&1 ||
+	echo "failed to set No_Atime flag on $lowerdir/testdir"
+
+# The NOATIME is inherited to children symlink in ext4/fs2fs
+# (and on tmpfs on recent kernels).
+# The overlayfs test will not fail unless base fs is
+# one of those filesystems.
+#
+# The problem with this inheritence is that the NOATIME flag is inherited
+# to a symlink and the flag does take effect, but there is no way to query
+# the flag (lsattr) or change it (chattr) on a symlink, so overlayfs will
+# fail when trying to copy up NOATIME flag from lower to upper symlink.
+#
+touch $lowerdir/testdir/foo
+ln -sf foo $lowerdir/testdir/lnk
+$LSATTR_PROG -l $lowerdir/testdir/foo >> $seqres.full
+
+before=$(stat -c %x $lowerdir/testdir/lnk)
+echo "symlink atime before readlink: $before" >> $seqres.full 2>&1
+cat $lowerdir/testdir/lnk
+after=$(stat -c %x $lowerdir/testdir/lnk)
+echo "symlink atime after readlink: $after" >> $seqres.full 2>&1
+
+[ "$before" == "$after" ] || \
+	_notrun "base fs $OVL_BASE_FSTYP does not inherit No_Atime flag on symlink"
+
+# mounting overlay
+_scratch_mount
+
+# moving symlink will try to copy up lower symlink flags
+# and fails with error ENXIO, if the bug is reproduced
+mv $SCRATCH_MNT/testdir/lnk $SCRATCH_MNT/
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/082.out b/tests/overlay/082.out
new file mode 100644
index 00000000..2977f141
--- /dev/null
+++ b/tests/overlay/082.out
@@ -0,0 +1,2 @@
+QA output created by 082
+Silence is golden
-- 
2.34.1