Add READDIRPLUS support

connection.go

@@ -151,6 +151,7 @@ func (c *Connection) Init() error {
 	cacheSymlinks := initOp.Flags&fusekernel.InitCacheSymlinks > 0
 	noOpenSupport := initOp.Flags&fusekernel.InitNoOpenSupport > 0
 	noOpendirSupport := initOp.Flags&fusekernel.InitNoOpendirSupport > 0
+	readdirplusSupport := initOp.Flags&fusekernel.InitDoReaddirplus > 0
 
 	// Respond to the init op.
 	initOp.Library = c.protocol
@@ -193,6 +194,11 @@ func (c *Connection) Init() error {
 		initOp.Flags |= fusekernel.InitNoOpendirSupport
 	}
 
+	// Tell the kernel to do readdirplus (readdir+lookup in one call)
+	if c.cfg.UseReadDirPlus && readdirplusSupport {
+		initOp.Flags |= fusekernel.InitDoReaddirplus
+	}
+
 	c.Reply(ctx, nil)
 	return nil
 }

conversions.go

@@ -341,6 +341,8 @@ func convertInMessage(
 		}
 		o = to
 
+	case fusekernel.OpReaddirplus:
+		fallthrough
 	case fusekernel.OpReaddir:
 		in := (*fusekernel.ReadIn)(inMsg.Consume(fusekernel.ReadInSize(protocol)))
 		if in == nil {
@@ -351,6 +353,7 @@ func convertInMessage(
 			Inode:     fuseops.InodeID(inMsg.Header().Nodeid),
 			Handle:    fuseops.HandleID(in.Fh),
 			Offset:    fuseops.DirOffset(in.Offset),
+			Plus:      inMsg.Header().Opcode == fusekernel.OpReaddirplus,
 			OpContext: fuseops.OpContext{Pid: inMsg.Header().Pid},
 		}
 		o = to

fuseops/ops.go

@@ -562,12 +562,18 @@ type ReadDirOp struct {
 	// offset, and return array offsets into that cached listing.
 	Offset DirOffset
 
+	// Whether this operation is a READDIRPLUS
+	//
+	// If true, then the FS must return inode attributes and expiration time
+	// along with each directory entry and increment its reference count.
+	Plus bool
+
 	// The destination buffer, whose length gives the size of the read.
 	//
 	// The output data should consist of a sequence of FUSE directory entries in
 	// the format generated by fuse_add_direntry (http://goo.gl/qCcHCV), which is
 	// consumed by parse_dirfile (http://goo.gl/2WUmD2). Use fuseutil.WriteDirent
-	// to generate this data.
+	// or fuseutil.WriteDirentPlus to generate this data.
 	//
 	// Each entry returned exposes a directory offset to the user that may later
 	// show up in ReadDirRequest.Offset. See notes on that field for more

fuseutil/dirent.go

@@ -19,6 +19,7 @@ import (
 	"unsafe"
 
 	"github.com/jacobsa/fuse/fuseops"
+	"github.com/jacobsa/fuse/internal/fusekernel"
 )
 
 type DirentType uint32
@@ -50,10 +51,18 @@ type Dirent struct {
 	Type DirentType
 }
 
-// Write the supplied directory entry intto the given buffer in the format
-// expected in fuseops.ReadFileOp.Data, returning the number of bytes written.
+// Write the supplied directory entry into the given buffer in the format
+// expected in fuseops.ReadDirOp.Data, returning the number of bytes written.
 // Return zero if the entry would not fit.
 func WriteDirent(buf []byte, d Dirent) (n int) {
+	return WriteDirentPlus(buf, nil, d)
+}
+
+// Write the supplied directory entry and, optionally, inode entry into the
+// given buffer in the format expected in fuseops.ReadDirOp.Data with enabled
+// READDIRPLUS capability, returning the number of bytes written.
+// Returns zero if the entry would not fit.
+func WriteDirentPlus(buf []byte, e *fuseops.ChildInodeEntry, d Dirent) (n int) {
 	// We want to write bytes with the layout of fuse_dirent
 	// (http://goo.gl/BmFxob) in host order. The struct must be aligned according
 	// to FUSE_DIRENT_ALIGN (http://goo.gl/UziWvH), which dictates 8-byte
@@ -78,10 +87,21 @@ func WriteDirent(buf []byte, d Dirent) (n int) {
 
 	// Do we have enough room?
 	totalLen := direntSize + len(d.Name) + padLen
+	if e != nil {
+		// READDIRPLUS was added in protocol 7.21, entry attributes were added in 7.9
+		// So here EntryOut is always full-length
+		totalLen += int(unsafe.Sizeof(fusekernel.EntryOut{}))
+	}
 	if totalLen > len(buf) {
 		return n
 	}
 
+	if e != nil {
+		out := (*fusekernel.EntryOut)(unsafe.Pointer(&buf[n]))
+		fuseops.ConvertChildInodeEntry(e, out)
+		n += int(unsafe.Sizeof(fusekernel.EntryOut{}))
+	}
+
 	// Write the header.
 	de := fuse_dirent{
 		ino:     uint64(d.Inode),

internal/fusekernel/fuse_kernel.go

@@ -417,6 +417,7 @@ const (
 	OpNotifyReply = 41
 	OpBatchForget = 42
 	OpFallocate   = 43
+	OpReaddirplus = 44
 
 	// OS X
 	OpSetvolname = 61

mount_config.go

@@ -151,6 +151,11 @@ type MountConfig struct {
 	// OpenDir calls at all (Linux >= 5.1):
 	EnableNoOpendirSupport bool
 
+	// Tell the kernel to use READDIRPLUS.
+	// Note that the implementation may still fall back to READDIR if the running
+	// kernel doesn't have support for READDIRPLUS.
+	UseReadDirPlus bool
+
 	// Disable FUSE default permissions.
 	// This is useful for situations where the backing data store (e.g., S3) doesn't
 	// actually utilise any form of qualifiable UNIX permissions.