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Subject[PATCH 4.14 30/72] elevator: lookup mq vs non-mq elevators
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 2527d99789e248576ac8081530cd4fd88730f8c7 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/elevator.c | 44 +++++++++++++++++++++-----------------------
1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 153926a90901..8320d97240be 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);
}

--
2.19.1


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