From 4bab928965e4c6411a96a9edaef484b53425fedb Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Fri, 22 Apr 2011 12:50:19 -0700
Subject: [PATCH] Disable spinup-avoidance measures for non-rotational disks

SSDs don't need to spin up or down, and they don't need the OS's help to
do sensible power management when idle; thus, the spinup-avoidance
measures increase the risk of data loss (by delaying writeback) without
saving power.  Add a new have_rotational_disks common function, and
check it from journal-commit, laptop-mode, and xfs_buffer; exit $NA if
the system has no rotational disks.
---
 pm/functions.in           |    9 +++++++++
 pm/power.d/journal-commit |    4 ++++
 pm/power.d/laptop-mode    |    1 +
 pm/power.d/xfs_buffer     |    3 +++
 4 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/pm/functions.in b/pm/functions.in
index bd649db..9efd071 100644
--- a/pm/functions.in
+++ b/pm/functions.in
@@ -249,3 +249,12 @@ dbus_send ()
 	command dbus-send "$@" 2>/dev/null || return $NA
 }
 
+have_rotational_disks ()
+{
+	for r in /sys/block/*/queue/rotational ; do
+		# Skip loop devices, which always show up as rotational
+		[ "${r#/sys/block/loop[0-9]}" != "$r" ] && continue
+		[ "$(cat "$r")" -eq 1 ] && return 0
+	done
+	return 1
+}
diff --git a/pm/power.d/journal-commit b/pm/power.d/journal-commit
index 5c0fc16..223228d 100644
--- a/pm/power.d/journal-commit
+++ b/pm/power.d/journal-commit
@@ -19,6 +19,10 @@ We currently only handle EXT3 filesystems
 EOF
 }
 
+# FIXME: This should really check the device corresponding to each filesystem.
+# However, most laptops only have one disk, so this works reasonably well.
+have_rotational_disks || exit $NA
+
 # actually remount the file system
 remount_fs()
 {
diff --git a/pm/power.d/laptop-mode b/pm/power.d/laptop-mode
index 601b260..07bb4f9 100644
--- a/pm/power.d/laptop-mode
+++ b/pm/power.d/laptop-mode
@@ -46,6 +46,7 @@ memory every 10 minutes if dirty memory never hits 40% of system memory.
 EOF
 }
 
+have_rotational_disks || exit $NA
 [ -w $VM/laptop_mode -a -w $VM/dirty_ratio ] || exit $NA
 
 read_values() {
diff --git a/pm/power.d/xfs_buffer b/pm/power.d/xfs_buffer
index d21e845..ad506b1 100644
--- a/pm/power.d/xfs_buffer
+++ b/pm/power.d/xfs_buffer
@@ -30,6 +30,9 @@ Defaults to 60000, or 10 minutes.
 EOF
 }
 
+# FIXME: This should really check the device corresponding to each filesystem.
+# However, most laptops only have one disk, so this works reasonably well.
+have_rotational_disks || exit $NA
 [ -f $XFS/age_buffer_centisecs ] || exit $NA
 
 read_values() {
-- 
1.7.4.4