[PATCH 1/5] staging: android: lowmemorykiller: Add config option to support oom_adj values

[John Stultz]

From: Arve Hjønnevåg <a...@android.com>

The conversion to use oom_score_adj instead of the deprecated oom_adj
values breaks existing user-space code. Add a config option to convert
oom_adj values written to oom_score_adj values if they appear to be
valid oom_adj values.

Cc: Android Kernel Team <kernel-t...@android.com>
Cc: Arve Hjønnevåg <a...@android.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Arve Hjønnevåg <a...@android.com>
Signed-off-by: John Stultz <john.stu...@linaro.org>
---
 drivers/staging/android/Kconfig           |    9 +++
 drivers/staging/android/lowmemorykiller.c |   85 +++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+)

diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
index 465a28c..5663c61 100644
--- a/drivers/staging/android/Kconfig
+++ b/drivers/staging/android/Kconfig
@@ -63,6 +63,15 @@ config ANDROID_LOW_MEMORY_KILLER
        ---help---
          Registers processes to be killed when memory is low
 
+config ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
+       bool "Android Low Memory Killer: detect oom_adj values"
+       depends on ANDROID_LOW_MEMORY_KILLER
+       default y
+       ---help---
+         Detect oom_adj values written to
+         /sys/module/lowmemorykiller/parameters/adj and convert them
+         to oom_score_adj values.
+
 config ANDROID_INTF_ALARM_DEV
        bool "Android alarm driver"
        depends on RTC_CLASS
diff --git a/drivers/staging/android/lowmemorykiller.c 
b/drivers/staging/android/lowmemorykiller.c
index 3b91b0f..7e00bdb 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -175,9 +175,94 @@ static void __exit lowmem_exit(void)
        unregister_shrinker(&lowmem_shrinker);
 }
 
+#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
+static short lowmem_oom_adj_to_oom_score_adj(short oom_adj)
+{
+       if (oom_adj == OOM_ADJUST_MAX)
+               return OOM_SCORE_ADJ_MAX;
+       else
+               return (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
+}
+
+static void lowmem_autodetect_oom_adj_values(void)
+{
+       int i;
+       short oom_adj;
+       short oom_score_adj;
+       int array_size = ARRAY_SIZE(lowmem_adj);
+
+       if (lowmem_adj_size < array_size)
+               array_size = lowmem_adj_size;
+
+       if (array_size <= 0)
+               return;
+
+       oom_adj = lowmem_adj[array_size - 1];
+       if (oom_adj > OOM_ADJUST_MAX)
+               return;
+
+       oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
+       if (oom_score_adj <= OOM_ADJUST_MAX)
+               return;
+
+       lowmem_print(1, "lowmem_shrink: convert oom_adj to oom_score_adj:\n");
+       for (i = 0; i < array_size; i++) {
+               oom_adj = lowmem_adj[i];
+               oom_score_adj = lowmem_oom_adj_to_oom_score_adj(oom_adj);
+               lowmem_adj[i] = oom_score_adj;
+               lowmem_print(1, "oom_adj %d => oom_score_adj %d\n",
+                            oom_adj, oom_score_adj);
+       }
+}
+
+static int lowmem_adj_array_set(const char *val, const struct kernel_param *kp)
+{
+       int ret;
+
+       ret = param_array_ops.set(val, kp);
+
+       /* HACK: Autodetect oom_adj values in lowmem_adj array */
+       lowmem_autodetect_oom_adj_values();
+
+       return ret;
+}
+
+static int lowmem_adj_array_get(char *buffer, const struct kernel_param *kp)
+{
+       return param_array_ops.get(buffer, kp);
+}
+
+static void lowmem_adj_array_free(void *arg)
+{
+       param_array_ops.free(arg);
+}
+
+static struct kernel_param_ops lowmem_adj_array_ops = {
+       .set = lowmem_adj_array_set,
+       .get = lowmem_adj_array_get,
+       .free = lowmem_adj_array_free,
+};
+
+static const struct kparam_array __param_arr_adj = {
+       .max = ARRAY_SIZE(lowmem_adj),
+       .num = &lowmem_adj_size,
+       .ops = &param_ops_short,
+       .elemsize = sizeof(lowmem_adj[0]),
+       .elem = lowmem_adj,
+};
+#endif
+
 module_param_named(cost, lowmem_shrinker.seeks, int, S_IRUGO | S_IWUSR);
+#ifdef CONFIG_ANDROID_LOW_MEMORY_KILLER_AUTODETECT_OOM_ADJ_VALUES
+__module_param_call(MODULE_PARAM_PREFIX, adj,
+                   &lowmem_adj_array_ops,
+                   .arr = &__param_arr_adj,
+                   S_IRUGO | S_IWUSR, -1);
+__MODULE_PARM_TYPE(adj, "array of short");
+#else
 module_param_array_named(adj, lowmem_adj, short, &lowmem_adj_size,
                         S_IRUGO | S_IWUSR);
+#endif
 module_param_array_named(minfree, lowmem_minfree, uint, &lowmem_minfree_size,
                         S_IRUGO | S_IWUSR);
 module_param_named(debug_level, lowmem_debug_level, uint, S_IRUGO | S_IWUSR);
-- 
1.7.10.4

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