| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <d05a1c0c-1212-17f4-3772-042e2ff76a40@freesources.org>
Date: Thu, 16 Jan 2020 12:53:54 +0100
From: Jonas Meurer <jonas@...esources.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: linux-kernel@...r.kernel.org, Linux PM <linux-pm@...r.kernel.org>,
Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
Tim Dittler <tim.dittler@...temli.org>,
Yannik Sembritzki <yannik@...britzki.me>,
"Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH v3] PM: suspend: Add sysfs attribute to control the "sync on
suspend" behavior
The sysfs attribute `/sys/power/sync_on_suspend` controls, whether or not
filesystems are synced by the kernel before system suspend.
Congruously, the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC
is slightly changed: It now defines the run-tim default for the new sysfs
attribute `/sys/power/sync_on_suspend`.
The run-time attribute is added because the existing corresponding
build-time Kconfig flag for (`CONFIG_SUSPEND_SKIP_SYNC`) is not flexible
enough. E.g. Linux distributions that provide pre-compiled kernels
usually want to stick with the default (sync filesystems before suspend)
but under special conditions this needs to be changed.
One example for such a special condition is user-space handling of
suspending block devices (e.g. using `cryptsetup luksSuspend` or `dmsetup
suspend`) before system suspend. The Kernel trying to sync filesystems
after the underlying block device already got suspended obviously leads
to dead-locks. Be aware that you have to take care of the filesystem sync
yourself before suspending the system in those scenarios.
Signed-off-by: Jonas Meurer <jonas@...esources.org>
---
Documentation/ABI/testing/sysfs-power | 13 +++++++++++
include/linux/suspend.h | 2 ++
kernel/power/Kconfig | 5 +++-
kernel/power/main.c | 33 +++++++++++++++++++++++++++
kernel/power/suspend.c | 2 +-
5 files changed, 53 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 6f87b9dd384b..9392a83afce8 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -407,3 +407,16 @@ Contact: Kalesh Singh <kaleshsingh96@...il.com>
Description:
The /sys/power/suspend_stats/last_failed_step file contains
the last failed step in the suspend/resume path.
+
+What: /sys/power/sync_on_suspend
+Date: October 2019
+Contact: Jonas Meurer <jonas@...esources.org>
+Description:
+ This file controls whether or not the kernel will sync()
+ filesystems during system suspend (after freezing user space
+ and before suspending devices).
+
+ 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/include/linux/suspend.h b/include/linux/suspend.h
index 6fc8843f1c9e..4a230c2f1c31 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -329,6 +329,7 @@ extern void arch_suspend_disable_irqs(void);
extern void arch_suspend_enable_irqs(void);
extern int pm_suspend(suspend_state_t state);
+extern bool sync_on_suspend_enabled;
#else /* !CONFIG_SUSPEND */
#define suspend_valid_only_mem NULL
@@ -342,6 +343,7 @@ static inline bool pm_suspend_default_s2idle(void) { return false; }
static inline void suspend_set_ops(const struct platform_suspend_ops *ops) {}
static inline int pm_suspend(suspend_state_t state) { return -ENOSYS; }
+static inline bool sync_on_suspend_enabled(void) { return true; }
static inline bool idle_should_enter_s2idle(void) { return false; }
static inline void __init pm_states_init(void) {}
static inline void s2idle_set_ops(const struct platform_s2idle_ops *ops) {}
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 e26de7af520b..69b7a8aeca3b 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -190,6 +190,38 @@ static ssize_t mem_sleep_store(struct kobject *kobj, struct kobj_attribute *attr
}
power_attr(mem_sleep);
+
+/*
+ * sync_on_suspend: invoke ksys_sync_helper() before suspend.
+ *
+ * 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 = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC);
+
+static ssize_t sync_on_suspend_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", sync_on_suspend_enabled);
+}
+
+static ssize_t sync_on_suspend_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ unsigned long val;
+
+ if (kstrtoul(buf, 10, &val))
+ return -EINVAL;
+
+ if (val > 1)
+ return -EINVAL;
+
+ sync_on_suspend_enabled = !!val;
+ return n;
+}
+
+power_attr(sync_on_suspend);
#endif /* CONFIG_SUSPEND */
#ifdef CONFIG_PM_SLEEP_DEBUG
@@ -855,6 +887,7 @@ static struct attribute * g[] = {
&wakeup_count_attr.attr,
#ifdef CONFIG_SUSPEND
&mem_sleep_attr.attr,
+ &sync_on_suspend_attr.attr,
#endif
#ifdef CONFIG_PM_AUTOSLEEP
&autosleep_attr.attr,
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index f3b7239f1892..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)) {
+ 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
Powered by blists - more mailing lists