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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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