add support for get-referring-entries

scoutfs now adds a new ioctl to get the parent id and some extra
info given an inode within the filesystem. This is less expensive
than the full path resolution for an inode, so can speed up cases
when the parent is all thats needed.

c_defs_linux.go

@@ -53,6 +53,8 @@ package scoutfs
 // typedef struct scoutfs_ioctl_alloc_detail scoutfs_ioctl_alloc_detail_t;
 // typedef struct scoutfs_ioctl_read_xattr_totals scoutfs_ioctl_read_xattr_totals_t;
 // typedef struct scoutfs_ioctl_xattr_total scoutfs_ioctl_xattr_total_t;
+// typedef struct scoutfs_ioctl_get_referring_entries scoutfs_ioctl_get_referring_entries_t;
+// typedef struct scoutfs_ioctl_dirent scoutfs_ioctl_dirent_t;
 //
 // // Go doesnt handle bitfields in structs, so we need to override the scoutfs
 // // struct definition here
@@ -81,6 +83,7 @@ const IOCDATAWAITERR = C.SCOUTFS_IOC_DATA_WAIT_ERR
 const IOCALLOCDETAIL = C.SCOUTFS_IOC_ALLOC_DETAIL
 const IOCMOVEBLOCKS = C.SCOUTFS_IOC_MOVE_BLOCKS
 const IOCREADXATTRTOTALS = C.SCOUTFS_IOC_READ_XATTR_TOTALS
+const IOCGETREFERRINGENTRIES = C.SCOUTFS_IOC_GET_REFERRING_ENTRIES
 
 const QUERYINODESMETASEQ = C.SCOUTFS_IOC_WALK_INODES_META_SEQ
 const QUERYINODESDATASEQ = C.SCOUTFS_IOC_WALK_INODES_DATA_SEQ
@@ -93,6 +96,8 @@ const SEARCHXATTRSOFLAGEND = C.SCOUTFS_SEARCH_XATTRS_OFLAG_END
 
 const MBSTAGEFLG = C.SCOUTFS_IOC_MB_STAGE
 
+const DIRENTFLAGLAST = C.SCOUTFS_IOCTL_DIRENT_FLAG_LAST
+
 type InodesEntry C.scoutfs_ioctl_walk_inodes_entry_t
 type queryInodes C.scoutfs_ioctl_walk_inodes_t
 type inoPath C.scoutfs_ioctl_ino_path_t
@@ -111,6 +116,8 @@ type allocDetailEntry C.scoutfs_ioctl_alloc_detail_entry_t
 type moveBlocks C.scoutfs_ioctl_move_blocks_t
 type readXattrTotals C.scoutfs_ioctl_read_xattr_totals_t
 type xattrTotal C.scoutfs_ioctl_xattr_total_t
+type getReferringEntries C.scoutfs_ioctl_get_referring_entries_t
+type scoutfsDirent C.scoutfs_ioctl_dirent_t
 
 const sizeofstatfsMore = C.sizeof_scoutfs_ioctl_statfs_more_t
 const sizeofxattrTotal = C.sizeof_scoutfs_ioctl_xattr_total_t

examples/getparents/main.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2018 Versity Software, Inc.
+//
+// Use of this source code is governed by a BSD-3-Clause license
+// that can be found in the LICENSE file in the root of the source
+// tree.
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+
+	scoutfs "github.com/versity/scoutfs-go"
+)
+
+func main() {
+	if len(os.Args) != 3 || os.Args[1] == "-h" {
+		fmt.Fprintln(os.Stderr, "usage:", os.Args[0], "<scoutfs mount point> <inode>")
+		os.Exit(1)
+	}
+
+	f, err := os.Open(os.Args[1])
+	if err != nil {
+		log.Fatalln("error open mount:", err)
+	}
+	defer f.Close()
+
+	u, err := strconv.ParseUint(os.Args[2], 10, 64)
+	if err != nil {
+		log.Fatalln("error parsing inode:", err)
+	}
+
+	s, err := scoutfs.GetParents(f, u, nil)
+	if err != nil {
+		log.Fatalln("error get parents:", err)
+	}
+
+	fmt.Println(s)
+}

scoutfs.go

@@ -10,6 +10,7 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -23,13 +24,14 @@ import (
 )
 
 const (
-	max64           = 0xffffffffffffffff
-	max32           = 0xffffffff
-	pathmax         = 4096
-	sysscoutfs      = "/sys/fs/scoutfs/"
-	statusfile      = "quorum/status"
-	listattrBufsize = 256 * 1024
-	scoutfsBS       = 4096
+	max64            = 0xffffffffffffffff
+	max32            = 0xffffffff
+	pathmax          = 4096
+	sysscoutfs       = "/sys/fs/scoutfs/"
+	statusfile       = "quorum/status"
+	listattrBufsize  = 256 * 1024
+	getparentBufsize = 4096 * 1024
+	scoutfsBS        = 4096
 	//leaderfile      = "quorum/is_leader"
 )
 
@@ -1019,3 +1021,116 @@ func (t *TotalsGroup) Reset() {
 	t.pos[1] = t.id2
 	t.pos[2] = 0
 }
+
+// Parent contains inode of parent and what the child inode is named within
+// this parent
+type Parent struct {
+	Ino  uint64 // Parent inode
+	Pos  uint64 // Entry directory position in parent
+	Type uint8  // Entry inode type matching DT_ enum values in readdir(3)
+	Ent  string // Entry name as known by parent
+}
+
+// GetParents returns all parents for the given inode
+// An open file within scoutfs is supplied for ioctls
+// (usually just the base mount point directory)
+// If passed in buffer is nil, call will allocate its own buffer.
+func GetParents(dirfd *os.File, ino uint64, b []byte) ([]Parent, error) {
+	if b == nil {
+		b = make([]byte, getparentBufsize)
+	}
+
+	gre := getReferringEntries{}
+
+	gre.Entries_bytes = uint64(len(b))
+	gre.Entries_ptr = uint64(uintptr(unsafe.Pointer(&b[0])))
+	gre.Ino = ino
+
+	var parents []Parent
+
+	for {
+		n, err := scoutfsctl(dirfd, IOCGETREFERRINGENTRIES, unsafe.Pointer(&gre))
+		if err != nil {
+			return nil, err
+		}
+		if n == 0 {
+			break
+		}
+
+		ents, isLast, err := parseDents(b)
+		if err != nil {
+			return nil, err
+		}
+
+		parents = append(parents, ents...)
+		if isLast {
+			break
+		}
+	}
+
+	return parents, nil
+}
+
+func parseDents(b []byte) ([]Parent, bool, error) {
+	r := bytes.NewReader(b)
+	var parents []Parent
+	var isLast bool
+	for {
+		var err error
+		var parent Parent
+		parent, isLast, err = parseDent(r)
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			return nil, false, err
+		}
+		parents = append(parents, parent)
+		if isLast {
+			break
+		}
+		if r.Len() == 0 {
+			break
+		}
+	}
+	return parents, isLast, nil
+}
+
+type dirent struct {
+	Dir_ino     uint64
+	Dir_pos     uint64
+	Ino         uint64
+	Entry_bytes uint16
+	Flags       uint8
+	D_type      uint8
+	Name_len    uint8
+}
+
+func parseDent(r *bytes.Reader) (Parent, bool, error) {
+	var dent dirent
+	err := binary.Read(r, binary.LittleEndian, &dent)
+	if err != nil {
+		return Parent{}, false, err
+	}
+
+	b := new(strings.Builder)
+	_, err = io.CopyN(b, r, int64(dent.Name_len))
+	if err != nil {
+		return Parent{}, false, err
+	}
+
+	pad := int(dent.Entry_bytes) - int(unsafe.Sizeof(dent)) + int(dent.Name_len)
+	for i := 0; i < pad; i++ {
+		_, err = r.ReadByte()
+		if err != nil {
+			return Parent{}, false, err
+		}
+	}
+
+	return Parent{
+		Ino:  dent.Dir_ino,
+		Pos:  dent.Dir_pos,
+		Type: dent.D_type,
+		Ent:  b.String(),
+	}, dent.Flags&DIRENTFLAGLAST == DIRENTFLAGLAST, nil
+}

scoutfsdefs.go

@@ -1,5 +1,5 @@
 // Code generated by cmd/cgo -godefs; DO NOT EDIT.
-// cgo -godefs /workspace/go/src/github.com/versity/scoutfs-go/c_defs_linux.go
+// cgo -godefs c_defs_linux.go
 
 package scoutfs
 
@@ -17,6 +17,7 @@ const IOCDATAWAITERR = 0x4030e80b
 const IOCALLOCDETAIL = 0x4010e80c
 const IOCMOVEBLOCKS = 0x4030e80d
 const IOCREADXATTRTOTALS = 0x4028e80f
+const IOCGETREFERRINGENTRIES = 0x4028e811
 
 const QUERYINODESMETASEQ = 0x0
 const QUERYINODESDATASEQ = 0x1
@@ -29,6 +30,8 @@ const SEARCHXATTRSOFLAGEND = 0x1
 
 const MBSTAGEFLG = 0x1
 
+const DIRENTFLAGLAST = 0x1
+
 type InodesEntry struct {
 	Major	uint64
 	Ino	uint64
@@ -157,6 +160,23 @@ type xattrTotal struct {
 	Total	uint64
 	Count	uint64
 }
+type getReferringEntries struct {
+	Ino		uint64
+	Dir_ino		uint64
+	Dir_pos		uint64
+	Entries_ptr	uint64
+	Entries_bytes	uint64
+}
+type scoutfsDirent struct {
+	Dir_ino		uint64
+	Dir_pos		uint64
+	Ino		uint64
+	Entry_bytes	uint16
+	Flags		uint8
+	D_type		uint8
+	Name_len	uint8
+	Name		[3]uint8
+}
 
 const sizeofstatfsMore = 0x30
 const sizeofxattrTotal = 0x28