[lxc-devel] [lxd/master] Make blkio limits more robust

[stgraber on Github]

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From af1239c6d8fa46838bff758823cdbddaff906fea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Fri, 5 Feb 2016 09:11:44 +0100
Subject: [PATCH] Make blkio limits more robust
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

Lets not completely fail startup/update on things the user cannot do
anything about. It's almost impossible to know what devices we can set
block limits on, so if we can't, just move on.

Closes #1568

Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 lxd/container_lxc.go | 68 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 43 insertions(+), 25 deletions(-)

diff --git a/lxd/container_lxc.go b/lxd/container_lxc.go
index 325bb41..50a21dd 100644
--- a/lxd/container_lxc.go
+++ b/lxd/container_lxc.go
@@ -563,37 +563,51 @@ func (c *containerLXC) initLXC() error {
 			}
 		}
 
-		diskLimits, err := c.getDiskLimits()
-		if err != nil {
-			return err
+		hasDiskLimits := false
+		for _, m := range c.expandedDevices {
+			if m["type"] != "disk" {
+				continue
+			}
+
+			if m["limits.read"] != "" || m["limits.write"] != "" || m["limits.max"] != "" {
+				hasDiskLimits = true
+				break
+			}
 		}
 
-		for block, limit := range diskLimits {
-			if limit.readBps > 0 {
-				err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.read_bps_device", fmt.Sprintf("%s %d", block, limit.readBps))
-				if err != nil {
-					return err
-				}
+		if hasDiskLimits {
+			diskLimits, err := c.getDiskLimits()
+			if err != nil {
+				return err
 			}
 
-			if limit.readIops > 0 {
-				err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.read_iops_device", fmt.Sprintf("%s %d", block, limit.readIops))
-				if err != nil {
-					return err
+			for block, limit := range diskLimits {
+				if limit.readBps > 0 {
+					err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.read_bps_device", fmt.Sprintf("%s %d", block, limit.readBps))
+					if err != nil {
+						return err
+					}
 				}
-			}
 
-			if limit.writeBps > 0 {
-				err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.write_bps_device", fmt.Sprintf("%s %d", block, limit.writeBps))
-				if err != nil {
-					return err
+				if limit.readIops > 0 {
+					err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.read_iops_device", fmt.Sprintf("%s %d", block, limit.readIops))
+					if err != nil {
+						return err
+					}
 				}
-			}
 
-			if limit.writeIops > 0 {
-				err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.write_iops_device", fmt.Sprintf("%s %d", block, limit.writeIops))
-				if err != nil {
-					return err
+				if limit.writeBps > 0 {
+					err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.write_bps_device", fmt.Sprintf("%s %d", block, limit.writeBps))
+					if err != nil {
+						return err
+					}
+				}
+
+				if limit.writeIops > 0 {
+					err = lxcSetConfigItem(cc, "lxc.cgroup.blkio.throttle.write_iops_device", fmt.Sprintf("%s %d", block, limit.writeIops))
+					if err != nil {
+						return err
+					}
 				}
 			}
 		}
@@ -3508,14 +3522,18 @@ func (c *containerLXC) getDiskLimits() (map[string]deviceBlockLimit, error) {
 		device := deviceBlockLimit{readBps: readBps, readIops: readIops, writeBps: writeBps, writeIops: writeIops}
 
 		for _, block := range blocks {
-			dev := strings.TrimPrefix(block, "/dev/")
+			if !strings.HasPrefix(block, "/dev/") {
+				continue
+			}
 
+			dev := strings.TrimPrefix(block, "/dev/")
 			if strings.Contains(dev, "/") {
 				continue
 			}
 
 			if !shared.PathExists(fmt.Sprintf("/sys/class/block/%s/dev", dev)) {
-				return nil, fmt.Errorf("Disk %s is missing /sys/class/block entry", dev)
+				shared.Log.Error("Disk is missing /sys/class/block entry", log.Ctx{"device": dev})
+				continue
 			}
 
 			block, err := ioutil.ReadFile(fmt.Sprintf("/sys/class/block/%s/dev", dev))