sysfs ->store is called with queue freezed, meantime we have several ->store() callbacks(update_nr_requests, wbt, scheduler) to allocate memory with GFP_KERNEL which may run into direct reclaim code path, then potential deadlock can be caused.

Fix the issue by marking NOIO around sysfs ->store()

Reported-by: Thomas Hellström thomas.hellstrom@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Ming Lei ming.lei@redhat.com --- block/blk-sysfs.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index e828be777206..e09b455874bf 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -681,6 +681,7 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr, struct queue_sysfs_entry *entry = to_queue(attr); struct gendisk *disk = container_of(kobj, struct gendisk, queue_kobj); struct request_queue *q = disk->queue; + unsigned int noio_flag; ssize_t res;

if (!entry->store_limit && !entry->store) @@ -711,7 +712,9 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,

mutex_lock(&q->sysfs_lock); blk_mq_freeze_queue(q); + noio_flag = memalloc_noio_save(); res = entry->store(disk, page, length); + memalloc_noio_restore(noio_flag); blk_mq_unfreeze_queue(q); mutex_unlock(&q->sysfs_lock); return res;