[RFC 2/6] PM: Hibernate: Add option to disable disk offset randomization

[Vivek Kumar]

Add a kernel parameter to disable the disk offset randomization
for SSD devices in which such feature is available at the
firmware level. This is helpful in improving hibernation
resume time.

Signed-off-by: Vivek Kumar <quic_vivekuma@xxxxxxxxxxx>
Signed-off-by: Prasanna Kumar <quic_kprasan@xxxxxxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++
 kernel/power/swap.c                             |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 666ade9..06b4f10 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5192,6 +5192,17 @@
 			Useful for devices that are detected asynchronously
 			(e.g. USB and MMC devices).
 
+	noswap_randomize
+			Kernel uses random disk offsets to help with wear-levelling
+			of SSD devices, while saving the hibernation snapshot image to
+			disk. Use this parameter to disable this feature for SSD
+			devices in scenarios when, such randomization is addressed at
+			the firmware level and hibenration image is not re-generated
+			frequently.
+			(Useful for improving hibernation resume time as snapshot pages
+			are available in disk serially and can be read in bigger chunks
+			without seeking)
+
 	retain_initrd	[RAM] Keep initrd memory after extraction
 
 	rfkill.default_state=
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 91fffdd..8d5c811 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -44,6 +44,7 @@ u32 swsusp_hardware_signature;
  */
 static bool clean_pages_on_read;
 static bool clean_pages_on_decompress;
+static bool noswap_randomize;
 
 /*
  *	The swap map is a data structure used for keeping track of each page
@@ -1616,3 +1617,11 @@ static int __init swsusp_header_init(void)
 }
 
 core_initcall(swsusp_header_init);
+
+static int __init noswap_randomize_setup(char *str)
+{
+	noswap_randomize = true;
+	return 1;
+}
+
+__setup("noswap_randomize", noswap_randomize_setup);
-- 
2.7.4