block, bfq: put async queues for root bfq groups too

[ Upstream commit 52257ffbfcaf58d247b13fb148e27ed17c33e526 ]

For each pair [device for which bfq is selected as I/O scheduler,
group in blkio/io], bfq maintains a corresponding bfq group. Each such
bfq group contains a set of async queues, with each async queue
created on demand, i.e., when some I/O request arrives for it.  On
creation, an async queue gets an extra reference, to make sure that
the queue is not freed as long as its bfq group exists.  Accordingly,
to allow the queue to be freed after the group exited, this extra
reference must released on group exit.

The above holds also for a bfq root group, i.e., for the bfq group
corresponding to the root blkio/io root for a given device. Yet, by
mistake, the references to the existing async queues of a root group
are not released when the latter exits. This causes a memory leak when
the instance of bfq for a given device exits. In a similar vein,
bfqg_stats_xfer_dead is not executed for a root group.

This commit fixes bfq_pd_offline so that the latter executes the above
missing operations for a root group too.

Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Reported-by: Guoqing Jiang <gqjiang@suse.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Davide Ferrari <davideferrari8@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index ceefb9a706d64c3a520c80fb39bc8265b1c144c0..5d53e504acae58d02fa3d8c0b5cef4b625e758aa 100644 (file)
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -749,10 +749,11 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
        unsigned long flags;
        int i;
 
+       spin_lock_irqsave(&bfqd->lock, flags);
+
        if (!entity) /* root group */
-               return;
+               goto put_async_queues;
 
-       spin_lock_irqsave(&bfqd->lock, flags);
        /*
         * Empty all service_trees belonging to this group before
         * deactivating the group itself.
@@ -783,6 +784,8 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
        }
 
        __bfq_deactivate_entity(entity, false);
+
+put_async_queues:
        bfq_put_async_queues(bfqd, bfqg);
 
        spin_unlock_irqrestore(&bfqd->lock, flags);