[PATCH v2] xfs_scrub_all.timer: don't run if /var/lib/xfsprogs is readonly

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

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

The xfs_scrub_all program wants to write a state file into the package
state dir to keep track of how recently it performed a media scan.
Don't allow the systemd timer to run if that path isn't writable.

Cc: <linux-xfs@vger.kernel.org> # v6.10.0
Fixes: 267ae610a3d90f ("xfs_scrub_all: enable periodic file data scrubs automatically")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
v2: add some comments to timer file
---
 scrub/Makefile               |    6 +++++-
 scrub/xfs_scrub_all.timer    |   16 ----------------
 scrub/xfs_scrub_all.timer.in |   23 +++++++++++++++++++++++
 3 files changed, 28 insertions(+), 17 deletions(-)
 delete mode 100644 scrub/xfs_scrub_all.timer
 create mode 100644 scrub/xfs_scrub_all.timer.in

diff --git a/scrub/Makefile b/scrub/Makefile
index 1e1109048c2a83..934b9062651bf1 100644
--- a/scrub/Makefile
+++ b/scrub/Makefile
@@ -108,10 +108,14 @@ endif
 # Automatically trigger a media scan once per month
 XFS_SCRUB_ALL_AUTO_MEDIA_SCAN_INTERVAL=1mo
 
-LDIRT = $(XFS_SCRUB_ALL_PROG) $(XFS_SCRUB_FAIL_PROG) *.service *.cron
+LDIRT = $(XFS_SCRUB_ALL_PROG) $(XFS_SCRUB_FAIL_PROG) *.service *.cron xfs_scrub_all.timer
 
 default: depend $(LTCOMMAND) $(XFS_SCRUB_ALL_PROG) $(XFS_SCRUB_FAIL_PROG) $(OPTIONAL_TARGETS)
 
+xfs_scrub_all.timer: xfs_scrub_all.timer.in $(builddefs)
+	@echo "    [SED]    $@"
+	$(Q)$(SED) -e "s|@pkg_state_dir@|$(PKG_STATE_DIR)|g" < $< > $@
+
 xfs_scrub_all: xfs_scrub_all.in $(builddefs)
 	@echo "    [SED]    $@"
 	$(Q)$(SED) -e "s|@sbindir@|$(PKG_SBIN_DIR)|g" \
diff --git a/scrub/xfs_scrub_all.timer b/scrub/xfs_scrub_all.timer
deleted file mode 100644
index f0c557fc380391..00000000000000
--- a/scrub/xfs_scrub_all.timer
+++ /dev/null
@@ -1,16 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0-or-later
-#
-# Copyright (C) 2018-2024 Oracle.  All Rights Reserved.
-# Author: Darrick J. Wong <djwong@kernel.org>
-
-[Unit]
-Description=Periodic XFS Online Metadata Check for All Filesystems
-
-[Timer]
-# Run on Sunday at 3:10am, to avoid running afoul of DST changes
-OnCalendar=Sun *-*-* 03:10:00
-RandomizedDelaySec=60
-Persistent=true
-
-[Install]
-WantedBy=timers.target
diff --git a/scrub/xfs_scrub_all.timer.in b/scrub/xfs_scrub_all.timer.in
new file mode 100644
index 00000000000000..a6bde69e947e23
--- /dev/null
+++ b/scrub/xfs_scrub_all.timer.in
@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2018-2025 Oracle.  All Rights Reserved.
+# Author: Darrick J. Wong <djwong@kernel.org>
+
+[Unit]
+Description=Periodic XFS Online Metadata Check for All Filesystems
+
+# The xfs_scrub_all program records the last time that it performed a media
+# scan in @pkg_state_dir@.  If this path is not writable, the program
+# aborts and systemd records this as a failure.  Disable the timer if the path
+# is not writable.  This should be an uncommon situation since most
+# readonly-root systems set that up to be writable (and possibly volatile).
+ConditionPathIsReadWrite=@pkg_state_dir@
+
+[Timer]
+# Run on Sunday at 3:10am, to avoid running afoul of DST changes
+OnCalendar=Sun *-*-* 03:10:00
+RandomizedDelaySec=60
+Persistent=true
+
+[Install]
+WantedBy=timers.target