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Subject[PATCH] 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/disk_offset that lets userspace
specify the offset and disk to use when initiating a hibernate
cycle.

Also split up the parsing routine to re-use the same code
for the /sys/power/resume and /sys/power/disk_offset parsing.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
---
Documentation/ABI/testing/sysfs-power | 43 +++++++++++++++++
Documentation/power/swsusp.txt | 10 +++-
kernel/power/hibernate.c | 88 +++++++++++++++++++++++++++++------
3 files changed, 125 insertions(+), 16 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 1e0d1da..9b66cd6 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -287,3 +287,46 @@ 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/disk_offset
+Date: April 2018
+Contact: Mario Limonciello <mario.limonciello@dell.com>
+Description:
+ This file is used for telling the kernel which disk partiion
+ and offset to use when hibernating the system.
+
+ Reads from this file will display the current disk and
+ 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 resume disk or offset.
+
+ Swap partition
+ --------------
+ You can write the partition to this file with no offset.
+
+ For example to use a swap partition you may write:
+ - "8:2" into the file.
+ or
+ - "/dev/sda2" into the file.
+ or
+ - "PARTUUID=a1386b9c-0d2a-41dd-bcf5-b9b19a863bfb" into the file
+
+ Note: writing a partition with no offset will also reset the
+ offset to zero.
+
+ Swap file
+ ---------
+ To use a swapfile you will need to write the partition
+ containing the swapfile along with a ";" and offset within
+ the partition that points to that file.
+
+ For example to use a swapfile located in the disk you
+ may write:
+ - "8:2;38416" into the file.
+ or
+ - "/dev/sda2;38416" into the file
+ or
+ - "PARTUUID=a1386b9c-0d2a-41dd-bcf5-b9b19a863bfb;38416" into
+ the file
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
index 9f2f942..539bb0b 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/disk_offset.
+
+Swap file:
+If using a swapfile you can also specify a resume offset usin
+resume_offset=<number> on the kernel command line or specify it after
+the disk with a ";<offset>" in /sys/power/disk_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..fc9dc7a 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1025,33 +1025,69 @@ static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr,

power_attr(disk);

+static int parse_device_input(const char *buf, size_t n, bool update_offset)
+{
+ char *start, *tok, *end;
+ int ret = -EINVAL;
+ dev_t res = 0;
+ int len = n;
+
+ if (!len)
+ return ret;
+ if (buf[len-1] == '\n')
+ len--;
+ start = end = kstrndup(buf, len, GFP_KERNEL);
+ if (!end)
+ return -ENOMEM;
+
+ tok = strsep(&end, ";");
+ if (!tok)
+ goto out;
+
+ res = name_to_dev_t(tok);
+ if (!res)
+ goto out;
+ ret = 0;
+
+ /* keep behavior for /sys/power/resume */
+ if (!update_offset)
+ goto out_name;
+
+ /* If no offset specified, reset it */
+ tok = strsep(&end, ";");
+ if (!tok) {
+ swsusp_resume_block = 0;
+ goto out_name;
+ }
+
+ ret = kstrtoull(tok, 0, (unsigned long long *) &swsusp_resume_block);
+ if (ret)
+ goto out;
+out_name:
+ swsusp_resume_device = res;
+out:
+ if (ret)
+ pr_warn("Unable to parse from %s (%d)", start, ret);
+ kfree(start);
+ return ret;
+}
+
static ssize_t resume_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
- return sprintf(buf,"%d:%d\n", MAJOR(swsusp_resume_device),
+ return sprintf(buf, "%d:%d\n", MAJOR(swsusp_resume_device),
MINOR(swsusp_resume_device));
}

static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t n)
{
- dev_t res;
- int len = n;
- char *name;
+ int rc = parse_device_input(buf, n, false);

- if (len && buf[len-1] == '\n')
- len--;
- name = kstrndup(buf, len, GFP_KERNEL);
- if (!name)
- return -ENOMEM;
-
- res = name_to_dev_t(name);
- kfree(name);
- if (!res)
- return -EINVAL;
+ if (rc < 0)
+ return rc;

lock_system_sleep();
- swsusp_resume_device = res;
unlock_system_sleep();
pr_info("Starting manual resume from disk\n");
noresume = 0;
@@ -1061,6 +1097,27 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,

power_attr(resume);

+static ssize_t disk_offset_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d:%d;%lu\n", MAJOR(swsusp_resume_device),
+ MINOR(swsusp_resume_device), swsusp_resume_block);
+}
+
+static ssize_t disk_offset_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf,
+ size_t n)
+{
+ int rc = parse_device_input(buf, n, true);
+
+ if (rc < 0)
+ return rc;
+
+ return n;
+}
+
+power_attr(disk_offset);
+
static ssize_t image_size_show(struct kobject *kobj, struct kobj_attribute *attr,
char *buf)
{
@@ -1106,6 +1163,7 @@ power_attr(reserved_size);

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