diff mbox

[1/3] elevator: lookup mq vs non-mq elevators

Message ID 1508954687-3204-2-git-send-email-axboe@kernel.dk (mailing list archive)
State New, archived
Headers show

Commit Message

Jens Axboe Oct. 25, 2017, 6:04 p.m. UTC 
If an IO scheduler is selected via elevator= and it doesn't match
the driver in question wrt blk-mq support, then we fail to boot.

The elevator= parameter is deprecated and only supported for
non-mq devices. Augment the elevator lookup API so that we
pass in if we're looking for an mq capable scheduler or not,
so that we only ever return a valid type for the queue in
question.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196695
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/elevator.c | 44 +++++++++++++++++++++-----------------------
 1 file changed, 21 insertions(+), 23 deletions(-)

Comments

Omar Sandoval Oct. 25, 2017, 6:27 p.m. UTC | #1 
On Wed, Oct 25, 2017 at 12:04:45PM -0600, Jens Axboe wrote:
> If an IO scheduler is selected via elevator= and it doesn't match
> the driver in question wrt blk-mq support, then we fail to boot.
> 
> The elevator= parameter is deprecated and only supported for
> non-mq devices. Augment the elevator lookup API so that we
> pass in if we're looking for an mq capable scheduler or not,
> so that we only ever return a valid type for the queue in
> question.
> 
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196695
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  block/elevator.c | 44 +++++++++++++++++++++-----------------------
>  1 file changed, 21 insertions(+), 23 deletions(-)
> 
> diff --git a/block/elevator.c b/block/elevator.c
> index 7ae50eb2732b..b70e69f795db 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -83,12 +83,15 @@ bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
>  }
>  EXPORT_SYMBOL(elv_bio_merge_ok);
>  
> -static struct elevator_type *elevator_find(const char *name)
> +/*
> + * Return scheduler with name 'name' and with matching 'mq capability
> + */
> +static struct elevator_type *elevator_find(const char *name, bool mq)
>  {
>  	struct elevator_type *e;
>  
>  	list_for_each_entry(e, &elv_list, list) {
> -		if (!strcmp(e->elevator_name, name))
> +		if (!strcmp(e->elevator_name, name) && !(mq ^ e->uses_mq))


How about just (mq == e->uses_mq)?

Besides that, Reviewed-by: Omar Sandoval <osandov@fb.com>

>  			return e;
>  	}
>
Jens Axboe Oct. 25, 2017, 6:31 p.m. UTC | #2 
On 10/25/2017 11:27 AM, Omar Sandoval wrote:
> On Wed, Oct 25, 2017 at 12:04:45PM -0600, Jens Axboe wrote:
>> If an IO scheduler is selected via elevator= and it doesn't match
>> the driver in question wrt blk-mq support, then we fail to boot.
>>
>> The elevator= parameter is deprecated and only supported for
>> non-mq devices. Augment the elevator lookup API so that we
>> pass in if we're looking for an mq capable scheduler or not,
>> so that we only ever return a valid type for the queue in
>> question.
>>
>> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196695
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>  block/elevator.c | 44 +++++++++++++++++++++-----------------------
>>  1 file changed, 21 insertions(+), 23 deletions(-)
>>
>> diff --git a/block/elevator.c b/block/elevator.c
>> index 7ae50eb2732b..b70e69f795db 100644
>> --- a/block/elevator.c
>> +++ b/block/elevator.c
>> @@ -83,12 +83,15 @@ bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
>>  }
>>  EXPORT_SYMBOL(elv_bio_merge_ok);
>>  
>> -static struct elevator_type *elevator_find(const char *name)
>> +/*
>> + * Return scheduler with name 'name' and with matching 'mq capability
>> + */
>> +static struct elevator_type *elevator_find(const char *name, bool mq)
>>  {
>>  	struct elevator_type *e;
>>  
>>  	list_for_each_entry(e, &elv_list, list) {
>> -		if (!strcmp(e->elevator_name, name))
>> +		if (!strcmp(e->elevator_name, name) && !(mq ^ e->uses_mq))
> 
> 
> How about just (mq == e->uses_mq)?

That is simpler/cleaner, I'll make that adjustment. Not sure where the XOR
temptation came from.
diff mbox

Patch

diff --git a/block/elevator.c b/block/elevator.c
index 7ae50eb2732b..b70e69f795db 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -83,12 +83,15 @@  bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
 }
 EXPORT_SYMBOL(elv_bio_merge_ok);
 
-static struct elevator_type *elevator_find(const char *name)
+/*
+ * Return scheduler with name 'name' and with matching 'mq capability
+ */
+static struct elevator_type *elevator_find(const char *name, bool mq)
 {
 	struct elevator_type *e;
 
 	list_for_each_entry(e, &elv_list, list) {
-		if (!strcmp(e->elevator_name, name))
+		if (!strcmp(e->elevator_name, name) && !(mq ^ e->uses_mq))
 			return e;
 	}
 
@@ -100,25 +103,25 @@  static void elevator_put(struct elevator_type *e)
 	module_put(e->elevator_owner);
 }
 
-static struct elevator_type *elevator_get(const char *name, bool try_loading)
+static struct elevator_type *elevator_get(struct request_queue *q,
+					  const char *name, bool try_loading)
 {
 	struct elevator_type *e;
 
 	spin_lock(&elv_list_lock);
 
-	e = elevator_find(name);
+	e = elevator_find(name, q->mq_ops != NULL);
 	if (!e && try_loading) {
 		spin_unlock(&elv_list_lock);
 		request_module("%s-iosched", name);
 		spin_lock(&elv_list_lock);
-		e = elevator_find(name);
+		e = elevator_find(name, q->mq_ops != NULL);
 	}
 
 	if (e && !try_module_get(e->elevator_owner))
 		e = NULL;
 
 	spin_unlock(&elv_list_lock);
-
 	return e;
 }
 
@@ -144,8 +147,12 @@  void __init load_default_elevator_module(void)
 	if (!chosen_elevator[0])
 		return;
 
+	/*
+	 * Boot parameter is deprecated, we haven't supported that for MQ.
+	 * Only look for non-mq schedulers from here.
+	 */
 	spin_lock(&elv_list_lock);
-	e = elevator_find(chosen_elevator);
+	e = elevator_find(chosen_elevator, false);
 	spin_unlock(&elv_list_lock);
 
 	if (!e)
@@ -202,7 +209,7 @@  int elevator_init(struct request_queue *q, char *name)
 	q->boundary_rq = NULL;
 
 	if (name) {
-		e = elevator_get(name, true);
+		e = elevator_get(q, name, true);
 		if (!e)
 			return -EINVAL;
 	}
@@ -214,7 +221,7 @@  int elevator_init(struct request_queue *q, char *name)
 	 * allowed from async.
 	 */
 	if (!e && !q->mq_ops && *chosen_elevator) {
-		e = elevator_get(chosen_elevator, false);
+		e = elevator_get(q, chosen_elevator, false);
 		if (!e)
 			printk(KERN_ERR "I/O scheduler %s not found\n",
 							chosen_elevator);
@@ -229,17 +236,17 @@  int elevator_init(struct request_queue *q, char *name)
 		 */
 		if (q->mq_ops) {
 			if (q->nr_hw_queues == 1)
-				e = elevator_get("mq-deadline", false);
+				e = elevator_get(q, "mq-deadline", false);
 			if (!e)
 				return 0;
 		} else
-			e = elevator_get(CONFIG_DEFAULT_IOSCHED, false);
+			e = elevator_get(q, CONFIG_DEFAULT_IOSCHED, false);
 
 		if (!e) {
 			printk(KERN_ERR
 				"Default I/O scheduler not found. " \
 				"Using noop.\n");
-			e = elevator_get("noop", false);
+			e = elevator_get(q, "noop", false);
 		}
 	}
 
@@ -905,7 +912,7 @@  int elv_register(struct elevator_type *e)
 
 	/* register, don't allow duplicate names */
 	spin_lock(&elv_list_lock);
-	if (elevator_find(e->elevator_name)) {
+	if (elevator_find(e->elevator_name, e->uses_mq)) {
 		spin_unlock(&elv_list_lock);
 		if (e->icq_cache)
 			kmem_cache_destroy(e->icq_cache);
@@ -1066,7 +1073,7 @@  static int __elevator_change(struct request_queue *q, const char *name)
 		return elevator_switch(q, NULL);
 
 	strlcpy(elevator_name, name, sizeof(elevator_name));
-	e = elevator_get(strstrip(elevator_name), true);
+	e = elevator_get(q, strstrip(elevator_name), true);
 	if (!e)
 		return -EINVAL;
 
@@ -1076,15 +1083,6 @@  static int __elevator_change(struct request_queue *q, const char *name)
 		return 0;
 	}
 
-	if (!e->uses_mq && q->mq_ops) {
-		elevator_put(e);
-		return -EINVAL;
-	}
-	if (e->uses_mq && !q->mq_ops) {
-		elevator_put(e);
-		return -EINVAL;
-	}
-
 	return elevator_switch(q, e);
 }