[PATCH v7 3/6] block/genhd.c: apply pm_runtime_set_memalloc_noio on block devices

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

This patch applyes the introduced pm_runtime_set_memalloc_noio on
block device so that PM core will teach mm to not allocate memory with
GFP_IOFS when calling the runtime_resume and runtime_suspend callback
for block devices and its ancestors.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
--
v5:
	- fix code style and one typo
v4:
	- call pm_runtime_set_memalloc_noio(ddev, true) after device_add
---
 block/genhd.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index 4125beb..2eb64a3 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -18,6 +18,7 @@
 #include <linux/mutex.h>
 #include <linux/idr.h>
 #include <linux/log2.h>
+#include <linux/pm_runtime.h>
 
 #include "blk.h"
 
@@ -534,6 +535,14 @@ static void register_disk(struct gendisk *disk)
 			return;
 		}
 	}
+
+	/*
+	 * avoid probable deadlock caused by allocating memory with
+	 * GFP_KERNEL in runtime_resume callback of its all ancestor
+	 * devices
+	 */
+	pm_runtime_set_memalloc_noio(ddev, true);
+
 	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
 	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);
 
@@ -663,6 +672,7 @@ void del_gendisk(struct gendisk *disk)
 	disk->driverfs_dev = NULL;
 	if (!sysfs_deprecated)
 		sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));
+	pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);
 	device_del(disk_to_dev(disk));
 }
 EXPORT_SYMBOL(del_gendisk);
-- 
1.7.9.5

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