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    Subject[PATCH 5.8 160/186] blk-stat: make q->stats->lock irqsafe
    Date
    From: Tejun Heo <tj@kernel.org>

    commit e11d80a849e010f78243bb6f6af7dccef3a71a90 upstream.

    blk-iocost calls blk_stat_enable_accounting() while holding an irqsafe lock
    which triggers a lockdep splat because q->stats->lock isn't irqsafe. Let's
    make it irqsafe.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Fixes: cd006509b0a9 ("blk-iocost: account for IO size when testing latencies")
    Cc: stable@vger.kernel.org # v5.8+
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    block/blk-stat.c | 17 +++++++++++------
    1 file changed, 11 insertions(+), 6 deletions(-)

    --- a/block/blk-stat.c
    +++ b/block/blk-stat.c
    @@ -137,6 +137,7 @@ void blk_stat_add_callback(struct reques
    struct blk_stat_callback *cb)
    {
    unsigned int bucket;
    + unsigned long flags;
    int cpu;

    for_each_possible_cpu(cpu) {
    @@ -147,20 +148,22 @@ void blk_stat_add_callback(struct reques
    blk_rq_stat_init(&cpu_stat[bucket]);
    }

    - spin_lock(&q->stats->lock);
    + spin_lock_irqsave(&q->stats->lock, flags);
    list_add_tail_rcu(&cb->list, &q->stats->callbacks);
    blk_queue_flag_set(QUEUE_FLAG_STATS, q);
    - spin_unlock(&q->stats->lock);
    + spin_unlock_irqrestore(&q->stats->lock, flags);
    }

    void blk_stat_remove_callback(struct request_queue *q,
    struct blk_stat_callback *cb)
    {
    - spin_lock(&q->stats->lock);
    + unsigned long flags;
    +
    + spin_lock_irqsave(&q->stats->lock, flags);
    list_del_rcu(&cb->list);
    if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
    blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
    - spin_unlock(&q->stats->lock);
    + spin_unlock_irqrestore(&q->stats->lock, flags);

    del_timer_sync(&cb->timer);
    }
    @@ -183,10 +186,12 @@ void blk_stat_free_callback(struct blk_s

    void blk_stat_enable_accounting(struct request_queue *q)
    {
    - spin_lock(&q->stats->lock);
    + unsigned long flags;
    +
    + spin_lock_irqsave(&q->stats->lock, flags);
    q->stats->enable_accounting = true;
    blk_queue_flag_set(QUEUE_FLAG_STATS, q);
    - spin_unlock(&q->stats->lock);
    + spin_unlock_irqrestore(&q->stats->lock, flags);
    }
    EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);


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