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Subject[PATCH v2 1/2] power/hibernate: Make passing hibernate offsets more friendly
Date
Currently the only way to specify a hibernate offset for a
swap file is on the kernel command line.

Add a new /sys/power/resume_offset that lets userspace
specify the offset and disk to use when initiating a hibernate
cycle.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
---
Documentation/ABI/testing/sysfs-power | 14 ++++++++++++++
Documentation/power/swsusp.txt | 10 +++++++++-
kernel/power/hibernate.c | 21 +++++++++++++++++++++
3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 1e0d1da..2f813d6 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -287,3 +287,17 @@ Description:
Writing a "1" to this file enables the debug messages and
writing a "0" (default) to it disables them. Reads from
this file return the current value.
+
+What: /sys/power/resume_offset
+Date: April 2018
+Contact: Mario Limonciello <mario.limonciello@dell.com>
+Description:
+ This file is used for telling the kernel an offset into a disk
+ to use when hibernating the system such as with a swap file.
+
+ Reads from this file will display the current offset
+ the kernel will be using on the next hibernation
+ attempt.
+
+ Using this sysfs file will override any values that were
+ set using the kernel command line for disk offset.
\ No newline at end of file
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index 9f2f942..cc87adf 100644
--- a/Documentation/power/swsusp.txt
+++ b/Documentation/power/swsusp.txt
@@ -24,8 +24,16 @@ Some warnings, first.
* see the FAQ below for details. (This is not true for more traditional
* power states like "standby", which normally don't turn USB off.)

+Swap partition:
You need to append resume=/dev/your_swap_partition to kernel command
-line. Then you suspend by
+line or specify it using /sys/power/resume.
+
+Swap file:
+If using a swapfile you can also specify a resume offset using
+resume_offset=<number> on the kernel command line or specify it
+in /sys/power/resume_offset.
+
+After preparing then you suspend by

echo shutdown > /sys/power/disk; echo disk > /sys/power/state

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index a5c36e9..16e8645 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1061,6 +1061,26 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,

power_attr(resume);

+static ssize_t resume_offset_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", swsusp_resume_block);
+}
+
+static ssize_t resume_offset_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf,
+ size_t n)
+{
+ int rc = kstrtoul(buf, 0, &swsusp_resume_block);
+
+ if (rc)
+ return rc;
+
+ return n;
+}
+
+power_attr(resume_offset);
+
static ssize_t image_size_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
@@ -1106,6 +1126,7 @@ power_attr(reserved_size);

static struct attribute * g[] = {
&disk_attr.attr,
+ &resume_offset_attr.attr,
&resume_attr.attr,
&image_size_attr.attr,
&reserved_size_attr.attr,
--
2.7.4
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