From 9072e1d38ac7f49e91e0570cc80000c48784ebc3 Mon Sep 17 00:00:00 2001
From: Chris Lu <chrislusf@users.noreply.github.com>
Date: Wed, 31 Dec 2025 00:30:12 -0800
Subject: [PATCH] mount: add -asyncDio flag for async direct I/O (#7922)

* mount: add -asyncDio flag for async direct I/O

This adds support for async direct I/O via the -asyncDio flag.

Async DIO enables the FUSE_CAP_ASYNC_DIO capability, allowing the kernel
to perform direct I/O operations asynchronously. This improves concurrency
for applications that use O_DIRECT flag.

Benefits:
- Better concurrency for direct I/O operations
- Improved performance for applications using O_DIRECT
- Reduced blocking on I/O operations

Use cases:
- Database workloads that use direct I/O
- Applications that bypass page cache intentionally
- High-performance I/O scenarios

Implementation inspired by JuiceFS which enables this capability
for improved I/O performance.

Usage:
  weed mount -filer=localhost:8888 -dir=/mnt/seaweedfs -asyncDio

* mount: add all remaining FUSE options (asyncDio, cacheSymlink, novncache)

This combines the remaining three FUSE mount options on top of the merged writebackCache PR:

1. asyncDio: Enable async direct I/O for better concurrency
2. cacheSymlink: Enable symlink caching to reduce metadata lookups
3. novncache: (macOS only) Disable vnode name caching to avoid stale data

All options use the function parameter 'option' instead of global 'mountOptions'.
---
 weed/command/mount.go     | 10 ++++++++++
 weed/command/mount_std.go | 10 +++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/weed/command/mount.go b/weed/command/mount.go
index 82b74f791..ddd429ccc 100644
--- a/weed/command/mount.go
+++ b/weed/command/mount.go
@@ -50,6 +50,11 @@ type MountOptions struct {
 
 	// FUSE performance options
 	writebackCache *bool
+	asyncDio       *bool
+	cacheSymlink   *bool
+
+	// macOS-specific FUSE options
+	novncache *bool
 }
 
 var (
@@ -108,6 +113,11 @@ func init() {
 
 	// FUSE performance options
 	mountOptions.writebackCache = cmdMount.Flag.Bool("writebackCache", false, "enable FUSE writeback cache for improved write performance (at risk of data loss on crash)")
+	mountOptions.asyncDio = cmdMount.Flag.Bool("asyncDio", false, "enable async direct I/O for better concurrency")
+	mountOptions.cacheSymlink = cmdMount.Flag.Bool("cacheSymlink", false, "enable symlink caching to reduce metadata lookups")
+
+	// macOS-specific FUSE options
+	mountOptions.novncache = cmdMount.Flag.Bool("sys.novncache", false, "(macOS only) disable vnode name caching to avoid stale data")
 }
 
 var cmdMount = &Command{
diff --git a/weed/command/mount_std.go b/weed/command/mount_std.go
index 7e688fc27..497a1eec8 100644
--- a/weed/command/mount_std.go
+++ b/weed/command/mount_std.go
@@ -208,7 +208,9 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		if runtime.GOARCH == "amd64" {
 			fuseMountOptions.Options = append(fuseMountOptions.Options, "noapplexattr")
 		}
-		// fuseMountOptions.Options = append(fuseMountOptions.Options, "novncache") // need to test effectiveness
+		if *option.novncache {
+			fuseMountOptions.Options = append(fuseMountOptions.Options, "novncache")
+		}
 		fuseMountOptions.Options = append(fuseMountOptions.Options, "slow_statfs")
 		fuseMountOptions.Options = append(fuseMountOptions.Options, "volname="+serverFriendlyName)
 		fuseMountOptions.Options = append(fuseMountOptions.Options, fmt.Sprintf("iosize=%d", ioSizeMB*1024*1024))
@@ -217,6 +219,12 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 	if *option.writebackCache {
 		fuseMountOptions.Options = append(fuseMountOptions.Options, "writeback_cache")
 	}
+	if *option.asyncDio {
+		fuseMountOptions.Options = append(fuseMountOptions.Options, "async_dio")
+	}
+	if *option.cacheSymlink {
+		fuseMountOptions.EnableSymlinkCaching = true
+	}
 
 	// find mount point
 	mountRoot := filerMountRootPath