virtiofs tweaks

cmd/incus-agent/events.go

@@ -4,14 +4,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
-	"os"
 	"strings"
 
 	"github.com/lxc/incus/internal/server/events"
 	"github.com/lxc/incus/internal/server/response"
 	"github.com/lxc/incus/shared/api"
 	"github.com/lxc/incus/shared/logger"
-	"github.com/lxc/incus/shared/subprocess"
 	"github.com/lxc/incus/shared/ws"
 )
 
@@ -144,8 +142,7 @@ func eventsProcess(event api.Event) {
 	// Attempt to perform the mount.
 	mntSource := fmt.Sprintf("incus_%s", e.Name)
 
-	_ = os.MkdirAll(e.Config["path"], 0755)
-	_, err = subprocess.RunCommand("mount", "-t", "virtiofs", mntSource, e.Config["path"])
+	err = tryMountShared(mntSource, e.Config["path"], "virtiofs", nil)
 	if err != nil {
 		logger.Infof("Failed to mount hotplug %q (Type: %q) to %q", mntSource, "virtiofs", e.Config["path"])
 		return

cmd/incus-agent/main_agent.go

@@ -278,54 +278,73 @@ func (c *cmdAgent) mountHostShares() {
 	}
 
 	for _, mount := range agentMounts {
-		// Convert relative mounts to absolute from / otherwise dir creation fails or mount fails.
-		if !strings.HasPrefix(mount.Target, "/") {
-			mount.Target = fmt.Sprintf("/%s", mount.Target)
+		if !slices.Contains([]string{"9p", "virtiofs"}, mount.FSType) {
+			logger.Infof("Unsupported mount fstype %q", mount.FSType)
+			continue
 		}
 
-		if !util.PathExists(mount.Target) {
-			err := os.MkdirAll(mount.Target, 0755)
-			if err != nil {
-				logger.Errorf("Failed to create mount target %q", mount.Target)
-				continue // Don't try to mount if mount point can't be created.
-			}
-		} else if linux.IsMountPoint(mount.Target) {
-			// Already mounted.
+		err = tryMountShared(mount.Source, mount.Target, mount.FSType, mount.Options)
+		if err != nil {
+			logger.Infof("Failed to mount %q (Type: %q, Options: %v) to %q: %v", mount.Source, "virtiofs", mount.Options, mount.Target, err)
 			continue
 		}
 
-		if mount.FSType == "9p" {
-			// Before mounting with 9p, try virtio-fs and use 9p as the fallback.
-			args := []string{"-t", "virtiofs", mount.Source, mount.Target}
-
-			for _, opt := range mount.Options {
-				// Ignore the transport and msize mount option as they are specific to 9p.
-				if strings.HasPrefix(opt, "trans=") || strings.HasPrefix(opt, "msize=") {
-					continue
-				}
+		logger.Infof("Mounted %q (Type: %q, Options: %v) to %q", mount.Source, mount.FSType, mount.Options, mount.Target)
+	}
+}
 
-				args = append(args, "-o", opt)
-			}
+func tryMountShared(src string, dst string, fstype string, opts []string) error {
+	// Convert relative mounts to absolute from / otherwise dir creation fails or mount fails.
+	if !strings.HasPrefix(dst, "/") {
+		dst = fmt.Sprintf("/%s", dst)
+	}
 
-			_, err = subprocess.RunCommand("mount", args...)
-			if err == nil {
-				logger.Infof("Mounted %q (Type: %q, Options: %v) to %q", mount.Source, "virtiofs", mount.Options, mount.Target)
-				continue
-			}
+	// Check mount path.
+	if !util.PathExists(dst) {
+		// Create the mount path.
+		err := os.MkdirAll(dst, 0755)
+		if err != nil {
+			return fmt.Errorf("Failed to create mount target %q", dst)
 		}
+	} else if linux.IsMountPoint(dst) {
+		// Already mounted.
+		return nil
+	}
 
-		args := []string{"-t", mount.FSType, mount.Source, mount.Target}
-
-		for _, opt := range mount.Options {
-			args = append(args, "-o", opt)
-		}
+	// Prepare the arguments.
+	sharedArgs := []string{}
+	p9Args := []string{}
 
-		_, err = subprocess.RunCommand("mount", args...)
-		if err != nil {
-			logger.Errorf("Failed mount %q (Type: %q, Options: %v) to %q: %v", mount.Source, mount.FSType, mount.Options, mount.Target, err)
+	for _, opt := range opts {
+		// transport and msize mount option are specific to 9p.
+		if strings.HasPrefix(opt, "trans=") || strings.HasPrefix(opt, "msize=") {
+			p9Args = append(p9Args, "-o", opt)
 			continue
 		}
 
-		logger.Infof("Mounted %q (Type: %q, Options: %v) to %q", mount.Source, mount.FSType, mount.Options, mount.Target)
+		sharedArgs = append(sharedArgs, "-o", opt)
+	}
+
+	// Always try virtiofs first.
+	args := []string{"-t", "virtiofs", src, dst}
+	args = append(args, sharedArgs...)
+
+	_, err := subprocess.RunCommand("mount", args...)
+	if err == nil {
+		return nil
+	} else if fstype == "virtiofs" {
+		return err
 	}
+
+	// Then fallback to 9p.
+	args = []string{"-t", "9p", src, dst}
+	args = append(args, sharedArgs...)
+	args = append(args, p9Args...)
+
+	_, err = subprocess.RunCommand("mount", args...)
+	if err != nil {
+		return err
+	}
+
+	return nil
 }

internal/server/device/device_utils_disk.go

@@ -500,7 +500,7 @@ func DiskVMVirtiofsdStart(execPath string, inst instance.Instance, socketPath st
 	defer func() { _ = unixFile.Close() }()
 
 	// Start the virtiofsd process in non-daemon mode.
-	args := []string{"--fd=3", "-o", fmt.Sprintf("source=%s", sharePath)}
+	args := []string{"--fd=3", "--cache=never", "-o", fmt.Sprintf("source=%s", sharePath)}
 	proc, err := subprocess.NewProcess(cmd, args, logPath, logPath)
 	if err != nil {
 		return nil, nil, err