dm mpath: remove process_queued_ios()

process_queued_ios() has served 3 functions:
  1) select pg and pgpath if none is selected
  2) start pg_init if requested
  3) dispatch queued IOs when pg is ready

Basically, a call to queue_work(process_queued_ios) can be replaced by
dm_table_run_md_queue_async(), which runs request queue and ends up
calling map_io(), which does 1), 2) and 3).

Exception is when !pg_ready() (which means either pg_init is running or
requested), then multipath_busy() prevents map_io() being called from
request_fn.

If pg_init is running, it should be ok as long as pg_init_done() does
the right thing when pg_init is completed, I.e.: restart pg_init if
!pg_ready() or call dm_table_run_md_queue_async() to kick map_io().

If pg_init is requested, we have to make sure the request is detected
and pg_init will be started.  pg_init is requested in 3 places:
  a) __choose_pgpath() in map_io()
  b) __choose_pgpath() in multipath_ioctl()
  c) pg_init retry in pg_init_done()
a) is ok because map_io() calls __pg_init_all_paths(), which does 2).
b) needs a call to __pg_init_all_paths(), which does 2).
c) needs a call to __pg_init_all_paths(), which does 2).

So this patch removes process_queued_ios() and ensures that
__pg_init_all_paths() is called at the appropriate locations.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>

1 files changed, 27 insertions, 42 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index e1c3ed31c9df..1c6a3f8da24d 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -93,8 +93,6 @@ struct multipath {
         unsigned pg_init_count;         /* Number of times pg_init called */
         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
 
-        struct work_struct process_queued_ios;
-
         struct work_struct trigger_event;
 
         /*
@@ -119,7 +117,6 @@ typedef int (*action_fn) (struct pgpath *pgpath);
 static struct kmem_cache *_mpio_cache;
 
 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
-static void process_queued_ios(struct work_struct *work);
 static void trigger_event(struct work_struct *work);
 static void activate_path(struct work_struct *work);
 static int __pgpath_busy(struct pgpath *pgpath);
@@ -197,7 +194,6 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
                 spin_lock_init(&m->lock);
                 m->queue_io = 1;
                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
-                INIT_WORK(&m->process_queued_ios, process_queued_ios);
                 INIT_WORK(&m->trigger_event, trigger_event);
                 init_waitqueue_head(&m->pg_init_wait);
                 mutex_init(&m->work_mutex);
@@ -254,16 +250,21 @@ static void clear_mapinfo(struct multipath *m, union map_info *info)
  * Path selection
  *-----------------------------------------------*/
 
-static void __pg_init_all_paths(struct multipath *m)
+static int __pg_init_all_paths(struct multipath *m)
 {
         struct pgpath *pgpath;
         unsigned long pg_init_delay = 0;
 
         if (m->pg_init_in_progress || m->pg_init_disabled)
-                return;
+                return 0;
 
         m->pg_init_count++;
         m->pg_init_required = 0;
+
+        /* Check here to reset pg_init_required */
+        if (!m->current_pg)
+                return 0;
+
         if (m->pg_init_delay_retry)
                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
@@ -275,6 +276,7 @@ static void __pg_init_all_paths(struct multipath *m)
                                        pg_init_delay))
                         m->pg_init_in_progress++;
         }
+        return m->pg_init_in_progress;
 }
 
 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
@@ -436,40 +438,13 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
                 m->saved_queue_if_no_path = queue_if_no_path;
         m->queue_if_no_path = queue_if_no_path;
         if (!m->queue_if_no_path)
-                queue_work(kmultipathd, &m->process_queued_ios);
+                dm_table_run_md_queue_async(m->ti->table);
 
         spin_unlock_irqrestore(&m->lock, flags);
 
         return 0;
 }
 
-static void process_queued_ios(struct work_struct *work)
-{
-        struct multipath *m =
-                container_of(work, struct multipath, process_queued_ios);
-        struct pgpath *pgpath = NULL;
-        unsigned must_queue = 1;
-        unsigned long flags;
-
-        spin_lock_irqsave(&m->lock, flags);
-
-        if (!m->current_pgpath)
-                __choose_pgpath(m, 0);
-
-        pgpath = m->current_pgpath;
-
-        if ((pgpath && !m->queue_io) ||
-            (!pgpath && !m->queue_if_no_path))
-                must_queue = 0;
-
-        if (pgpath && m->pg_init_required)
-                __pg_init_all_paths(m);
-
-        spin_unlock_irqrestore(&m->lock, flags);
-        if (!must_queue)
-                dm_table_run_md_queue_async(m->ti->table);
-}
-
 /*
  * An event is triggered whenever a path is taken out of use.
  * Includes path failure and PG bypass.
@@ -1016,7 +991,7 @@ static int reinstate_path(struct pgpath *pgpath)
 
         if (!m->nr_valid_paths++) {
                 m->current_pgpath = NULL;
-                queue_work(kmultipathd, &m->process_queued_ios);
+                dm_table_run_md_queue_async(m->ti->table);
         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
                         m->pg_init_in_progress++;
@@ -1212,11 +1187,12 @@ static void pg_init_done(void *data, int errors)
                 /* Activations of other paths are still on going */
                 goto out;
 
-        if (!m->pg_init_required)
-                m->queue_io = 0;
-
-        m->pg_init_delay_retry = delay_retry;
-        queue_work(kmultipathd, &m->process_queued_ios);
+        if (m->pg_init_required) {
+                m->pg_init_delay_retry = delay_retry;
+                if (__pg_init_all_paths(m))
+                        goto out;
+        }
+        m->queue_io = 0;
 
         /*
          * Wake up any thread waiting to suspend.
@@ -1592,8 +1568,17 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
                         r = err;
         }
 
-        if (r == -ENOTCONN && !fatal_signal_pending(current))
-                queue_work(kmultipathd, &m->process_queued_ios);
+        if (r == -ENOTCONN && !fatal_signal_pending(current)) {
+                spin_lock_irqsave(&m->lock, flags);
+                if (!m->current_pg) {
+                        /* Path status changed, redo selection */
+                        __choose_pgpath(m, 0);
+                }
+                if (m->pg_init_required)
+                        __pg_init_all_paths(m);
+                spin_unlock_irqrestore(&m->lock, flags);
+                dm_table_run_md_queue_async(m->ti->table);
+        }
 
         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 }