[v4,13/22] multipathd: fix "fail path" and "reinstate path" commands

Commit Message

Benjamin Marzinski Oct. 9, 2024, 1:15 a.m. UTC

Now that multipathd can drop the vecs lock and sleep in-between when the
checker runs and when the path gets updated, it is possible for the
user to either fail or reinstate the path in this window.

If a path gets manually failed in the window between when the checker
starts and the path is updated, the checker will have already been
started, on the path, and if multipathd read the results like normal,
it could simply reinstate the path. To avoid this, when a path checker
is disabled, the checker path_state and message are updated, just
like they are when checker_check() is run on a disabled path, so that
when checker_get_state() is called, it will always return the same
results for a disabled checker, regardless of when it was disabled.

Reinstating the path doesn't cause many problems, but still can be
improved. Since the checker was disabled when it would have been
started, it didn't run during this cycle, only the kernel state will get
updated. The rest of the path update changes won't happen until the next
time the checker runs. This is the case regardless of whether or not the
path was reinstated in the window between when the checker starts and
the path is updated. To make reinstated paths get updated sooner,
pp->tick is now set to 1 when the path is reinstated.

Reviewed-by: Martin Wilck <[e-mail]>
Signed-off-by: Benjamin Marzinski <[e-mail]>
---
 libmultipath/checkers.c   | 2 ++
 multipathd/cli_handlers.c | 1 +
 2 files changed, 3 insertions(+)

Patch

diff --git a/libmultipath/checkers.c b/libmultipath/checkers.c
index ce3e48bd..f3e98352 100644
--- a/libmultipath/checkers.c
+++ b/libmultipath/checkers.c
@@ -251,6 +251,8 @@  void checker_disable (struct checker * c)
 	if (!c)
 		return;
 	c->disable = 1;
+	c->msgid = CHECKER_MSGID_DISABLED;
+	c->path_state = PATH_UNCHECKED;
 }
 
 int checker_init (struct checker * c, void ** mpctxt_addr)
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index 42603544..184c3f91 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -1108,6 +1108,7 @@  cli_reinstate(void * v, struct strbuf *reply, void * data)
 		pp->mpp->alias, pp->dev_t);
 
 	checker_enable(&pp->checker);
+	pp->tick = 1;
 	return dm_reinstate_path(pp->mpp->alias, pp->dev_t);
 }