dm mpath: push path selector locking down to path selectors

Proper locking of the lists used by the path selectors should be handled
within the selectors (relying on dm-mpath.c code's use of the m->lock
spinlock was reckless).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-queue-length.c

@@ -29,6 +29,7 @@
 struct selector {
 	struct list_head	valid_paths;
 	struct list_head	failed_paths;
+	spinlock_t lock;
 };
 
 struct path_info {
@@ -45,6 +46,7 @@ static struct selector *alloc_selector(void)
 	if (s) {
 		INIT_LIST_HEAD(&s->valid_paths);
 		INIT_LIST_HEAD(&s->failed_paths);
+		spin_lock_init(&s->lock);
 	}
 
 	return s;
@@ -113,6 +115,7 @@ static int ql_add_path(struct path_selector *ps, struct dm_path *path,
 	struct path_info *pi;
 	unsigned repeat_count = QL_MIN_IO;
 	char dummy;
+	unsigned long flags;
 
 	/*
 	 * Arguments: [<repeat_count>]
@@ -147,7 +150,9 @@ static int ql_add_path(struct path_selector *ps, struct dm_path *path,
 
 	path->pscontext = pi;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_add_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -156,16 +161,22 @@ static void ql_fail_path(struct path_selector *ps, struct dm_path *path)
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move(&pi->list, &s->failed_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path)
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -178,9 +189,12 @@ static struct dm_path *ql_select_path(struct path_selector *ps,
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = NULL, *best = NULL;
+	struct dm_path *ret = NULL;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	if (list_empty(&s->valid_paths))
-		return NULL;
+		goto out;
 
 	/* Change preferred (first in list) path to evenly balance. */
 	list_move_tail(s->valid_paths.next, &s->valid_paths);
@@ -195,11 +209,14 @@ static struct dm_path *ql_select_path(struct path_selector *ps,
 	}
 
 	if (!best)
-		return NULL;
+		goto out;
 
 	*repeat_count = best->repeat_count;
 
-	return best->path;
+	ret = best->path;
+out:
+	spin_unlock_irqrestore(&s->lock, flags);
+	return ret;
 }
 
 static int ql_start_io(struct path_selector *ps, struct dm_path *path,

drivers/md/dm-round-robin.c

@@ -46,6 +46,7 @@ static void free_paths(struct list_head *paths)
 struct selector {
 	struct list_head valid_paths;
 	struct list_head invalid_paths;
+	spinlock_t lock;
 };
 
 static struct selector *alloc_selector(void)
@@ -55,6 +56,7 @@ static struct selector *alloc_selector(void)
 	if (s) {
 		INIT_LIST_HEAD(&s->valid_paths);
 		INIT_LIST_HEAD(&s->invalid_paths);
+		spin_lock_init(&s->lock);
 	}
 
 	return s;
@@ -74,7 +76,7 @@ static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
 
 static void rr_destroy(struct path_selector *ps)
 {
-	struct selector *s = (struct selector *) ps->context;
+	struct selector *s = ps->context;
 
 	free_paths(&s->valid_paths);
 	free_paths(&s->invalid_paths);
@@ -111,10 +113,11 @@ static int rr_status(struct path_selector *ps, struct dm_path *path,
 static int rr_add_path(struct path_selector *ps, struct dm_path *path,
 		       int argc, char **argv, char **error)
 {
-	struct selector *s = (struct selector *) ps->context;
+	struct selector *s = ps->context;
 	struct path_info *pi;
 	unsigned repeat_count = RR_MIN_IO;
 	char dummy;
+	unsigned long flags;
 
 	if (argc > 1) {
 		*error = "round-robin ps: incorrect number of arguments";
@@ -144,25 +147,33 @@ static int rr_add_path(struct path_selector *ps, struct dm_path *path,
 
 	path->pscontext = pi;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_add_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
 
 static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
 {
-	struct selector *s = (struct selector *) ps->context;
+	unsigned long flags;
+	struct selector *s = ps->context;
 	struct path_info *pi = p->pscontext;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move(&pi->list, &s->invalid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
 {
-	struct selector *s = (struct selector *) ps->context;
+	unsigned long flags;
+	struct selector *s = ps->context;
 	struct path_info *pi = p->pscontext;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -170,14 +181,17 @@ static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
 static struct dm_path *rr_select_path(struct path_selector *ps,
 				      unsigned *repeat_count, size_t nr_bytes)
 {
-	struct selector *s = (struct selector *) ps->context;
+	unsigned long flags;
+	struct selector *s = ps->context;
 	struct path_info *pi = NULL;
 
+	spin_lock_irqsave(&s->lock, flags);
 	if (!list_empty(&s->valid_paths)) {
 		pi = list_entry(s->valid_paths.next, struct path_info, list);
 		list_move_tail(&pi->list, &s->valid_paths);
 		*repeat_count = pi->repeat_count;
 	}
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return pi ? pi->path : NULL;
 }

drivers/md/dm-service-time.c

@@ -24,6 +24,7 @@
 struct selector {
 	struct list_head valid_paths;
 	struct list_head failed_paths;
+	spinlock_t lock;
 };
 
 struct path_info {
@@ -41,6 +42,7 @@ static struct selector *alloc_selector(void)
 	if (s) {
 		INIT_LIST_HEAD(&s->valid_paths);
 		INIT_LIST_HEAD(&s->failed_paths);
+		spin_lock_init(&s->lock);
 	}
 
 	return s;
@@ -111,6 +113,7 @@ static int st_add_path(struct path_selector *ps, struct dm_path *path,
 	unsigned repeat_count = ST_MIN_IO;
 	unsigned relative_throughput = 1;
 	char dummy;
+	unsigned long flags;
 
 	/*
 	 * Arguments: [<repeat_count> [<relative_throughput>]]
@@ -160,7 +163,9 @@ static int st_add_path(struct path_selector *ps, struct dm_path *path,
 
 	path->pscontext = pi;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_add_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -169,16 +174,22 @@ static void st_fail_path(struct path_selector *ps, struct dm_path *path)
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move(&pi->list, &s->failed_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 }
 
 static int st_reinstate_path(struct path_selector *ps, struct dm_path *path)
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = path->pscontext;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	list_move_tail(&pi->list, &s->valid_paths);
+	spin_unlock_irqrestore(&s->lock, flags);
 
 	return 0;
 }
@@ -265,9 +276,12 @@ static struct dm_path *st_select_path(struct path_selector *ps,
 {
 	struct selector *s = ps->context;
 	struct path_info *pi = NULL, *best = NULL;
+	struct dm_path *ret = NULL;
+	unsigned long flags;
 
+	spin_lock_irqsave(&s->lock, flags);
 	if (list_empty(&s->valid_paths))
-		return NULL;
+		goto out;
 
 	/* Change preferred (first in list) path to evenly balance. */
 	list_move_tail(s->valid_paths.next, &s->valid_paths);
@@ -277,11 +291,14 @@ static struct dm_path *st_select_path(struct path_selector *ps,
 			best = pi;
 
 	if (!best)
-		return NULL;
+		goto out;
 
 	*repeat_count = best->repeat_count;
 
-	return best->path;
+	ret = best->path;
+out:
+	spin_unlock_irqrestore(&s->lock, flags);
+	return ret;
 }
 
 static int st_start_io(struct path_selector *ps, struct dm_path *path,