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elevator: lookup mq vs non-mq elevators 

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
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2017-10-25 12:33:42 -06:00
parent d5ce4c31d6
commit 2527d99789
1 changed files with 21 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
block/elevator.c
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@ -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);
}