[PATCH V2] block: mark GFP_NOIO around sysfs ->store()

[Ming Lei <ming.lei@redhat.com>]

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()

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reported-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Closes: https://lore.kernel.org/linux-block/ead7c5ce5138912c1f3179d62370b84a64014a38.camel@linux.intel.com/
Fixes: bd166ef183c2 ("blk-mq-sched: add framework for MQ capable IO schedulers")
Cc: stable@vger.kernel.org
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
V2:
	- add Closes & Reviewed-by & Fixes tag

 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;
-- 
2.44.0