[PATCH 2/2] PM: CONFIG_SUSPEND_SKIP_SYNC sets default for, '/sys/power/sync_on_suspend'

[Jonas Meurer <jonas@freesources.org>]

Slightly change the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC:
Make it configure the default for '/sys/power/sync_on_suspend', now that we
have a run-time switch for it.

Signed-off-by: Jonas Meurer <jonas@freesources.org>
---
 Documentation/ABI/testing/sysfs-power | 7 ++++---
 kernel/power/Kconfig                  | 5 ++++-
 kernel/power/main.c                   | 2 +-
 kernel/power/suspend.c                | 2 +-
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index f164a364e89a..783b3ce8eb06 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -418,6 +418,7 @@ Description:
 		aware that you have to take care of sync() yourself before
 		suspending the system if you disable it here.
 
-		Writing a "1" (default) to this file enables the sync() and
-		writing a "0" disables it. Reads from the file return the
-		current value.
+		Writing a "1" to this file enables the sync() and writing a
+		"0" disables it. Reads from the file return the current value.
+		The default is "1" but can be configured with the build-time
+		config flag "SUSPEND_SKIP_SYNC".
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index d3667b4075c1..7cbfbeacd68a 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -27,7 +27,10 @@ config SUSPEND_SKIP_SYNC
 	  Skip the kernel sys_sync() before freezing user processes.
 	  Some systems prefer not to pay this cost on every invocation
 	  of suspend, or they are content with invoking sync() from
-	  user-space before invoking suspend.  Say Y if that's your case.
+	  user-space before invoking suspend.  There's a run-time switch
+	  at '/sys/power/sync_on_suspend' to configure this behaviour.
+	  This setting changes the default for the run-tim switch. Say Y
+	  to change the default to disable the kernel sys_sync().
 
 config HIBERNATE_CALLBACKS
 	bool
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 7d9d579a8e6f..69b7a8aeca3b 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -197,7 +197,7 @@ power_attr(mem_sleep);
  * show() returns whether ksys_sync_helper() is invoked before suspend.
  * store() accepts 0 or 1.  0 disables ksys_sync_helper() and 1 enables it.
  */
-bool sync_on_suspend_enabled = true;
+bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC);
 
 static ssize_t sync_on_suspend_show(struct kobject *kobj,
 				   struct kobj_attribute *attr, char *buf)
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 503d56419a69..2c47280fbfc7 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -564,7 +564,7 @@ static int enter_state(suspend_state_t state)
 	if (state == PM_SUSPEND_TO_IDLE)
 		s2idle_begin();
 
-	if (!IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC) && sync_on_suspend_enabled) {
+	if (sync_on_suspend_enabled) {
 		trace_suspend_resume(TPS("sync_filesystems"), 0, true);
 		ksys_sync_helper();
 		trace_suspend_resume(TPS("sync_filesystems"), 0, false);
-- 
2.20.1