[PATCH 1/3] xfs_scrub: automatic downgrades to dry-run mode in service mode

Darrick J. Wong
2023-12-31T23:00:25Z

When service mode is enabled, xfs_scrub is being run within the context
of a systemd service. The service description language doesn't have any
particularly good constructs for adding in a '-n' argument if the
filesystem is readonly, which means that xfs_scrub is passed a path, and
needs to switch to dry-run mode on its own if the fs is mounted
readonly or the kernel doesn't support repairs.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
scrub/phase1.c | 13 +++++++++++++
scrub/repair.c | 33 +++++++++++++++++++++++++++++++++
scrub/repair.h | 2 ++
3 files changed, 48 insertions(+)

diff --git a/scrub/phase1.c b/scrub/phase1.c
index 516d929d626..095c045915a 100644
--- a/scrub/phase1.c
+++ b/scrub/phase1.c
@@ -216,6 +216,19 @@ _("Kernel metadata scrubbing facility is not available."));
return ECANCELED;
}

+ /*
+ * Normally, callers are required to pass -n if the provided path is a
+ * readonly filesystem or the kernel wasn't built with online repair
+ * enabled. However, systemd services are not scripts and cannot
+ * determine either of these conditions programmatically. Change the
+ * behavior to dry-run mode if either condition is detected.
+ */
+ if (repair_want_service_downgrade(ctx)) {
+ str_info(ctx, ctx->mntpoint,
+_("Filesystem cannot be repaired in service mode, downgrading to dry-run mode."));
+ ctx->mode = SCRUB_MODE_DRY_RUN;
+ }
+
/* Do we need kernel-assisted metadata repair? */
if (ctx->mode != SCRUB_MODE_DRY_RUN && !can_repair(ctx)) {
str_error(ctx, ctx->mntpoint,
diff --git a/scrub/repair.c b/scrub/repair.c
index 19f5c9052af..2883f98af4a 100644
--- a/scrub/repair.c
+++ b/scrub/repair.c
@@ -45,6 +45,39 @@ static const unsigned int repair_deps[XFS_SCRUB_TYPE_NR] = {
};
#undef DEP

+/*
+ * Decide if we want an automatic downgrade to dry-run mode. This is only
+ * for service mode, where we are fed a path and have to figure out if the fs
+ * is repairable or not.
+ */
+bool
+repair_want_service_downgrade(
+ struct scrub_ctx *ctx)
+{
+ struct xfs_scrub_metadata meta = {
+ .sm_type = XFS_SCRUB_TYPE_PROBE,
+ .sm_flags = XFS_SCRUB_IFLAG_REPAIR,
+ };
+ int error;
+
+ if (ctx->mode == SCRUB_MODE_DRY_RUN)
+ return false;
+ if (!is_service)
+ return false;
+ if (debug_tweak_on("XFS_SCRUB_NO_KERNEL"))
+ return false;
+
+ error = -xfrog_scrub_metadata(&ctx->mnt, &meta);
+ switch (error) {
+ case EROFS:
+ case ENOTRECOVERABLE:
+ case EOPNOTSUPP:
+ return true;
+ }
+
+ return false;
+}
+
/* Repair some metadata. */
static int
xfs_repair_metadata(
diff --git a/scrub/repair.h b/scrub/repair.h
index a685e90374c..411a379f6fa 100644
--- a/scrub/repair.h
+++ b/scrub/repair.h
@@ -102,4 +102,6 @@ repair_item_completely(
return repair_item(ctx, sri, XRM_FINAL_WARNING | XRM_NOPROGRESS);
}

+bool repair_want_service_downgrade(struct scrub_ctx *ctx);
+
#endif /* XFS_SCRUB_REPAIR_H_ */