[PATCH v7 5/6] PM / Runtime: force memory allocation with no I/O during Runtime PM callbcack

[Ming Lei]

This patch applies the introduced memalloc_noio_save() and
memalloc_noio_restore() to force memory allocation with no I/O
during runtime_resume/runtime_suspend callback on device with
the flag of 'memalloc_noio' set.

Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxx>
Cc: Rafael J. Wysocki <rjw@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
--
v7:
	- move memalloc_noio_save/memalloc_noio_restore into
	rpm_callback to avoid code duplication, as suggested
	by Rafael
v5:
	- use inline memalloc_noio_save()
v4:
	- runtime_suspend need this too because rpm_resume may wait for
	completion of concurrent runtime_suspend, so deadlock still may
	be triggered in runtime_suspend path.
---
 drivers/base/power/runtime.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index cd92e1c..1244930 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -348,7 +348,24 @@ static int rpm_callback(int (*cb)(struct device *), struct device *dev)
 	if (!cb)
 		return -ENOSYS;
 
-	retval = __rpm_callback(cb, dev);
+	if (dev->power.memalloc_noio) {
+		unsigned int noio_flag;
+
+		/*
+		 * Deadlock might be caused if memory allocation with
+		 * GFP_KERNEL happens inside runtime_suspend and
+		 * runtime_resume callbacks of one block device's
+		 * ancestor or the block device itself. Network
+		 * device might be thought as part of iSCSI block
+		 * device, so network device and its ancestor should
+		 * be marked as memalloc_noio too.
+		 */
+		noio_flag = memalloc_noio_save();
+		retval = __rpm_callback(cb, dev);
+		memalloc_noio_restore(noio_flag);
+	} else {
+		retval = __rpm_callback(cb, dev);
+	}
 
 	dev->power.runtime_error = retval;
 	return retval != -EACCES ? retval : -EIO;
-- 
1.7.9.5

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