linux-kernel - [PATCH] thermal: sysfs: fall back to vzalloc for cooling device's statistics

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Date:   Tue, 18 Aug 2020 14:30:04 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     rui.zhang@...el.com, daniel.lezcano@...aro.org,
        amit.kucheria@...durent.com, viresh.kumar@...aro.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        huyue2@...ong.com, zbestahu@....com
Subject: [PATCH] thermal: sysfs: fall back to vzalloc for cooling device's statistics

From: Yue Hu <huyue2@...ong.com>

We observed warning about kzalloc() when register thermal cooling device
in backlight_device_register(). backlight display can be a cooling device
since reducing screen brightness will can help reduce temperature.

However, ->get_max_state of backlight will assign max brightness of 1024
to states. The memory size can be getting 1MB+ due to states * states.
That is so large to trigger kmalloc() warning.

So, let's remove it and try vzalloc() if kzalloc() fails.

Signed-off-by: Yue Hu <huyue2@...ong.com>
---
 drivers/thermal/thermal_sysfs.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index aa99edb..9bae0b6 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -16,6 +16,8 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
 #include <linux/string.h>
 #include <linux/jiffies.h>
 
@@ -919,7 +921,9 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
 	var += sizeof(*stats->time_in_state) * states;
 	var += sizeof(*stats->trans_table) * states * states;
 
-	stats = kzalloc(var, GFP_KERNEL);
+	stats = kzalloc(var, GFP_KERNEL | __GFP_NOWARN);
+	if (!stats)
+		stats = vzalloc(var);
 	if (!stats)
 		return;
 
@@ -938,7 +942,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
 
 static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
 {
-	kfree(cdev->stats);
+	kvfree(cdev->stats);
 	cdev->stats = NULL;
 }
 
-- 
1.9.1