runc exec: fix setting process.ioPriority

Commit bfbd0305b added IOPriority field into both Config and Process,
but forgot to add a mechanism to actually use Process.IOPriority.
As a result, runc exec does not set Process.IOPriority ever.

Fix it, and a test case (which fails before the fix).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

CHANGELOG.md

@@ -17,6 +17,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
    IDs before calling libcontainer; it is recommended to use Go package
    github.com/moby/sys/user for that. (#3999)
 
+### Fixed
+ * `runc exec -p` no longer ignores specified `ioPriority` setting.
+   Similarly, libcontainer's `Container.Start` and `Container.Run`
+   methods no longer ignore `Process.IOPriority` setting. (#4585)
+
 ## [1.2.0] - 2024-10-22
 
 > できるときにできることをやるんだ。それが今だ。

libcontainer/container_linux.go

@@ -707,6 +707,7 @@ func (c *Container) newInitConfig(process *Process) *initConfig {
 		AppArmorProfile:  c.config.AppArmorProfile,
 		ProcessLabel:     c.config.ProcessLabel,
 		Rlimits:          c.config.Rlimits,
+		IOPriority:       c.config.IOPriority,
 		CreateConsole:    process.ConsoleSocket != nil,
 		ConsoleWidth:     process.ConsoleWidth,
 		ConsoleHeight:    process.ConsoleHeight,
@@ -729,6 +730,9 @@ func (c *Container) newInitConfig(process *Process) *initConfig {
 	if len(process.Rlimits) > 0 {
 		cfg.Rlimits = process.Rlimits
 	}
+	if process.IOPriority != nil {
+		cfg.IOPriority = process.IOPriority
+	}
 
 	// Set misc properties.
 

libcontainer/init_linux.go

@@ -81,6 +81,7 @@ type initConfig struct {
 	NoNewPrivileges bool                  `json:"no_new_privileges"`
 	ProcessLabel    string                `json:"process_label"`
 	Rlimits         []configs.Rlimit      `json:"rlimits"`
+	IOPriority      *configs.IOPriority   `json:"io_priority,omitempty"`
 
 	// Miscellaneous properties, filled in by [Container.newInitConfig]
 	// unless documented otherwise.
@@ -623,7 +624,7 @@ func setupScheduler(config *configs.Config) error {
 	return nil
 }
 
-func setupIOPriority(config *configs.Config) error {
+func setupIOPriority(config *initConfig) error {
 	const ioprioWhoPgrp = 1
 
 	ioprio := config.IOPriority

libcontainer/process.go

@@ -114,6 +114,9 @@ type Process struct {
 
 	Scheduler *configs.Scheduler
 
+	// IOPriority is a process I/O priority.
+	//
+	// If not empty, takes precedence over container's [configs.Config.IOPriority].
 	IOPriority *configs.IOPriority
 }
 

libcontainer/setns_init_linux.go

@@ -75,7 +75,7 @@ func (l *linuxSetnsInit) Init() error {
 		return err
 	}
 
-	if err := setupIOPriority(l.config.Config); err != nil {
+	if err := setupIOPriority(l.config); err != nil {
 		return err
 	}
 	// Tell our parent that we're ready to exec. This must be done before the

libcontainer/standard_init_linux.go

@@ -159,7 +159,7 @@ func (l *linuxStandardInit) Init() error {
 		return err
 	}
 
-	if err := setupIOPriority(l.config.Config); err != nil {
+	if err := setupIOPriority(l.config); err != nil {
 		return err
 	}
 

tests/integration/ioprio.bats

@@ -20,11 +20,25 @@ function teardown() {
 	# Check the init process.
 	runc exec test_ioprio ionice -p 1
 	[ "$status" -eq 0 ]
-	[[ "$output" = *'best-effort: prio 4'* ]]
+	[ "${lines[0]}" = 'best-effort: prio 4' ]
 
-	# Check the process made from the exec command.
+	# Check an exec process, which should derive ioprio from config.json.
 	runc exec test_ioprio ionice
 	[ "$status" -eq 0 ]
+	[ "${lines[0]}" = 'best-effort: prio 4' ]
 
-	[[ "$output" = *'best-effort: prio 4'* ]]
+	# Check an exec with a priority taken from process.json,
+	# which should override the ioprio in config.json.
+	proc='
+{
+	"terminal": false,
+	"ioPriority": {
+		"class": "IOPRIO_CLASS_IDLE"
+	},
+	"args": [ "/usr/bin/ionice" ],
+	"cwd": "/"
+}'
+	runc exec --process <(echo "$proc") test_ioprio
+	[ "$status" -eq 0 ]
+	[ "${lines[0]}" = 'idle' ]
 }