[dm-devel] [PATCH] multipath-tools: prevent a kernel upgrade leading to all paths lost

[Brian Bunker]

With the kernel commit 268940b80fa4096397fd0a28e6ad807e64120215, the
handling of ALUA state transitioning state changed. It used to be that
paths which returned with ALUA transitioning state would not result in
those paths being failed. With this patch, that state returned will
result in the path being failed. The result of this will result in all
paths down events when a configuration has the no_path_retry set to 0.
Before this kernel change that same configuration would not reach all
paths down.

If the kernel is not changed back to the previous behavior, the
multipath-tools have to protect against this condition or
configurations which were working correctly prior to the kernel change
will lead to an unexpected failure.

See the kernel discussions here:
https://marc.info/?l=linux-scsi&m=162636826305740&w=2
https://marc.info/?l=linux-scsi&m=164987222322261&w=2

Signed-off-by: brian at purestorage.com
Reviewed-by: sconnor at purestorage.com
___
diff --git a/libmultipath/structs.h b/libmultipath/structs.h
index d94f93a0..0af7e598 100644
--- a/libmultipath/structs.h
+++ b/libmultipath/structs.h
@@ -370,6 +370,7 @@ struct multipath {
        int failback_tick;

        int no_path_retry; /* number of retries after all paths are down */
+       int no_path_retry_configured; /* value in config */
        int retry_tick;    /* remaining times for retries */
        int disable_queueing;
        int minio;
diff --git a/libmultipath/structs_vec.c b/libmultipath/structs_vec.c
index 6c23df86..3db4e6f7 100644
--- a/libmultipath/structs_vec.c
+++ b/libmultipath/structs_vec.c
@@ -780,8 +780,15 @@ void update_queue_mode_add_path(struct multipath *mpp)
 {
        int active = count_active_paths(mpp);

-       if (active > 0)
+       if (active > 0) {
                leave_recovery_mode(mpp);
+               if (mpp->no_path_retry != mpp->no_path_retry_configured) {
+                       condlog(2, "%s: return no path retry to %d
from %d", mpp->alias,
+                       mpp->no_path_retry_configured, mpp->no_path_retry);
+                       mpp->no_path_retry = mpp->no_path_retry_configured;
+               }
+       }
+
        condlog(2, "%s: remaining active paths: %d", mpp->alias, active);
 }

diff --git a/multipathd/main.c b/multipathd/main.c
index f2c0b280..92841d13 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -524,7 +524,7 @@ int update_multipath (struct vectors *vecs, char
*mapname, int reset)
        struct multipath *mpp;
        struct pathgroup  *pgp;
        struct path *pp;
-       int i, j;
+       int i, j, tpg;

        mpp = find_mp_by_alias(vecs->mpvec, mapname);

@@ -553,6 +553,15 @@ int update_multipath (struct vectors *vecs, char
*mapname, int reset)
                                checkint = conf->checkint;
                                put_multipath_config(conf);
                                condlog(2, "%s: mark as failed", pp->dev);
+                               tpg = get_target_port_group(pp, DEF_TIMEOUT);
+                               if ((tpg >= 0) &&
+                                   (mpp->no_path_retry == 0) &&
+                                   (get_asymmetric_access_state(pp,
tpg, DEF_TIMEOUT) == AAS_TRANSITIONING)) {
+                                       mpp->no_path_retry_configured
= mpp->no_path_retry;
+                                       mpp->no_path_retry = (60 / checkint);
+                                       condlog(2, "%s: changed %s no
path retry to %d", pp->dev, mpp->alias,
+                                               (60 / checkint));
+                               }
                                mpp->stat_path_failures++;
                                pp->state = PATH_DOWN;
                                if (oldstate == PATH_UP ||
___

-- 
Brian Bunker
PURE Storage, Inc.
brian at purestorage.com