Fixed scheduler activation (bsc#1052770)

Do not activate the new scheduler for devices
which do not support it.

- 3.3.0

package/yast2-tune.changes

@@ -1,3 +1,10 @@
+-------------------------------------------------------------------
+Mon Aug 14 18:19:47 UTC 2017 - lslezak@suse.cz
+
+- Fixed scheduler activation: do not activate the new scheduler
+  for devices which do not support it (bsc#1052770)
+- 3.3.0
+
 -------------------------------------------------------------------
 Fri Jan 20 16:21:30 UTC 2017 - mvidner@suse.com
 

package/yast2-tune.spec

@@ -17,7 +17,7 @@
 
 
 Name:           yast2-tune
-Version:        3.2.0
+Version:        3.3.0
 Release:        0
 
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build

src/modules/SystemSettings.rb

@@ -248,11 +248,38 @@ def activate_scheduler
       # activate the scheduler for all disk devices
       return if new_elevator == :missing
       Dir["/sys/block/*/queue/scheduler"].each do |f|
+        # skip devices which do not support the selected scheduler,
+        # keep the original scheduler
+        next unless device_supports_scheduler(f, new_elevator)
+
         log.info("Activating scheduler '#{new_elevator}' for device #{f}")
         File.write(f, new_elevator)
       end
     end
 
+    # read available schedulers for the device
+    # @param device [String] path to device scheduler file
+    # @return [Array<String>] read schedulers from the file
+    def read_device_schedulers(device)
+      schedulers = File.read(device).split(/\s+/).map do |sched|
+        # remove the current scheduler marks [] around the name
+        sched[0] == "[" && sched [-1] == "]" ? sched[1..-2] : sched
+      end
+
+      log.info("Available schedulers for #{device}: #{schedulers}")
+
+      schedulers
+    end
+
+    # does the device support support the scheduler?
+    # @param device [String] path to device scheduler file
+    # @param scheduler [String] name of the requested scheduler
+    # @return [Boolean] true if supported
+    def device_supports_scheduler(device, scheduler)
+      schedulers = read_device_schedulers(device)
+      schedulers.include?(scheduler)
+    end
+
     # Read IO scheduler configuration updating the module's value
     #
     # @see Read

test/system_settings_test.rb

@@ -123,13 +123,14 @@
     let(:sysrq_keys) { false }
     let(:scheduler)  { "" }
     let(:disk)       { "/sys/block/sda/queue/scheduler" }
+    let(:disk2)      { "/sys/block/sdb/queue/scheduler" }
 
     before do
       settings.SetSysRqKeysEnabled(sysrq_keys)
       settings.SetIOScheduler(scheduler)
       allow(Yast::Bootloader).to receive(:modify_kernel_params)
       allow(Yast::Bootloader).to receive(:proposed_cfg_changed=)
-      allow(Dir).to receive(:[]).with(/scheduler/).and_return([disk])
+      allow(Dir).to receive(:[]).with(/scheduler/).and_return([disk, disk2])
     end
 
     context "when SysRq keys status is unknown" do
@@ -161,6 +162,8 @@
 
       before do
         allow(File).to receive(:write).with(KERNEL_SYSRQ_FILE, anything)
+        allow(File).to receive(:read).with(disk).and_return("noop deadline [cfq]")
+        allow(File).to receive(:read).with(disk2).and_return("noop deadline [cfq]")
       end
 
       it "updates bootloader configuration" do
@@ -173,6 +176,16 @@
 
       it "activates scheduler for all disk devices" do
         expect(File).to receive(:write).with(disk, scheduler)
+        expect(File).to receive(:write).with(disk2, scheduler)
+        settings.Activate
+      end
+
+      it "does not activate the scheduler if the device does not support it" do
+        # make the "cfq" scheduler unsupported
+        expect(File).to receive(:read).with(disk2).and_return("[mq-deadline] none")
+        expect(File).to receive(:write).with(disk, scheduler)
+        # ensure it is not changed
+        expect(File).to_not receive(:write).with(disk2, scheduler)
         settings.Activate
       end
     end