block: add proper helpers for elevator_type module refcount management

Make sure we have helpers for all relevant module refcount operations on
the elevator_type in elevator.h, and use them.  Move the call to the get
helper in blk_mq_elv_switch_none a bit so that it is obvious with a less
verbose comment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221020064819.1469928-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 33292c0..9db8814 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4554,17 +4554,10 @@ static bool blk_mq_elv_switch_none(struct list_head *head,
 
        INIT_LIST_HEAD(&qe->node);
        qe->q = q;
+       /* keep a reference to the elevator module as we'll switch back */
+       __elevator_get(qe->type);
        qe->type = q->elevator->type;
        list_add(&qe->node, head);
-
-       /*
-        * After elevator_switch, the previous elevator_queue will be
-        * released by elevator_release. The reference of the io scheduler
-        * module get by elevator_get will also be put. So we need to get
-        * a reference of the io scheduler module here to prevent it to be
-        * removed.
-        */
-       __module_get(qe->type->elevator_owner);
        elevator_switch(q, NULL);
        mutex_unlock(&q->sysfs_lock);
 

diff --git a/block/elevator.c b/block/elevator.c
index 9e12706..8fb404a 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -132,11 +132,6 @@ static struct elevator_type *elevator_find(const char *name,
        return NULL;
 }
 
-static void elevator_put(struct elevator_type *e)
-{
-       module_put(e->elevator_owner);
-}
-
 static struct elevator_type *elevator_get(struct request_queue *q,
                                          const char *name, bool try_loading)
 {
@@ -152,7 +147,7 @@ static struct elevator_type *elevator_get(struct request_queue *q,
                e = elevator_find(name, q->required_elevator_features);
        }
 
-       if (e && !try_module_get(e->elevator_owner))
+       if (e && !elevator_tryget(e))
                e = NULL;
 
        spin_unlock(&elv_list_lock);
@@ -659,7 +654,7 @@ static struct elevator_type *elevator_get_by_features(struct request_queue *q)
                }
        }
 
-       if (found && !try_module_get(found->elevator_owner))
+       if (found && !elevator_tryget(found))
                found = NULL;
 
        spin_unlock(&elv_list_lock);

diff --git a/block/elevator.h b/block/elevator.h
index 7538247..774a8f6 100644 (file)
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -84,6 +84,21 @@ struct elevator_type
        struct list_head list;
 };
 
+static inline bool elevator_tryget(struct elevator_type *e)
+{
+       return try_module_get(e->elevator_owner);
+}
+
+static inline void __elevator_get(struct elevator_type *e)
+{
+       __module_get(e->elevator_owner);
+}
+
+static inline void elevator_put(struct elevator_type *e)
+{
+       module_put(e->elevator_owner);
+}
+
 #define ELV_HASH_BITS 6
 
 void elv_rqhash_del(struct request_queue *q, struct request *rq);