dm mpath: add mutex to synchronize adding and flushing work

Add a mutex to allow possible creators of new work to synchronize with
flushing work queues.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Acked-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 38 insertions, 21 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 5b23f2df9bde..700154e21483 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -93,6 +93,8 @@ struct multipath {
          * can resubmit bios on error.
          */
         mempool_t *mpio_pool;
+
+        struct mutex work_mutex;
 };
 
 /*
@@ -198,6 +200,7 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
                 m->queue_io = 1;
                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
                 INIT_WORK(&m->trigger_event, trigger_event);
+                mutex_init(&m->work_mutex);
                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
                 if (!m->mpio_pool) {
                         kfree(m);
@@ -1268,7 +1271,11 @@ static void multipath_presuspend(struct dm_target *ti)
 
 static void multipath_postsuspend(struct dm_target *ti)
 {
+        struct multipath *m = ti->private;
+
+        mutex_lock(&m->work_mutex);
         flush_multipath_work();
+        mutex_unlock(&m->work_mutex);
 }
 
 /*
@@ -1407,51 +1414,61 @@ static int multipath_status(struct dm_target *ti, status_type_t type,
 
 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
 {
-        int r;
+        int r = -EINVAL;
         struct dm_dev *dev;
         struct multipath *m = (struct multipath *) ti->private;
         action_fn action;
 
+        mutex_lock(&m->work_mutex);
+
         if (argc == 1) {
-                if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
-                        return queue_if_no_path(m, 1, 0);
-                else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
-                        return queue_if_no_path(m, 0, 0);
+                if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
+                        r = queue_if_no_path(m, 1, 0);
+                        goto out;
+                } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
+                        r = queue_if_no_path(m, 0, 0);
+                        goto out;
+                }
         }
 
-        if (argc != 2)
-                goto error;
+        if (argc != 2) {
+                DMWARN("Unrecognised multipath message received.");
+                goto out;
+        }
 
-        if (!strnicmp(argv[0], MESG_STR("disable_group")))
-                return bypass_pg_num(m, argv[1], 1);
-        else if (!strnicmp(argv[0], MESG_STR("enable_group")))
-                return bypass_pg_num(m, argv[1], 0);
-        else if (!strnicmp(argv[0], MESG_STR("switch_group")))
-                return switch_pg_num(m, argv[1]);
-        else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
+        if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
+                r = bypass_pg_num(m, argv[1], 1);
+                goto out;
+        } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
+                r = bypass_pg_num(m, argv[1], 0);
+                goto out;
+        } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
+                r = switch_pg_num(m, argv[1]);
+                goto out;
+        } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
                 action = reinstate_path;
         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
                 action = fail_path;
-        else
-                goto error;
+        else {
+                DMWARN("Unrecognised multipath message received.");
+                goto out;
+        }
 
         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
                           dm_table_get_mode(ti->table), &dev);
         if (r) {
                 DMWARN("message: error getting device %s",
                        argv[1]);
-                return -EINVAL;
+                goto out;
         }
 
         r = action_dev(m, dev, action);
 
         dm_put_device(ti, dev);
 
+out:
+        mutex_unlock(&m->work_mutex);
         return r;
-
-error:
-        DMWARN("Unrecognised multipath message received.");
-        return -EINVAL;
 }
 
 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,