wip fuse

1 files changed, 190 insertions, 0 deletions

diff --git a/cmd/btrfs-mount/main.go b/cmd/btrfs-mount/main.go
new file mode 100644
index 0000000..8e07e77
--- /dev/null
+++ b/cmd/btrfs-mount/main.go
@@ -0,0 +1,190 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+
+	"github.com/datawire/dlib/dcontext"
+	"github.com/datawire/dlib/dgroup"
+	"github.com/datawire/dlib/dlog"
+	"github.com/jacobsa/fuse"
+	"github.com/jacobsa/fuse/fuseops"
+	"github.com/jacobsa/fuse/fuseutil"
+	"github.com/sirupsen/logrus"
+
+	"lukeshu.com/btrfs-tools/pkg/btrfs"
+	"lukeshu.com/btrfs-tools/pkg/btrfs/btrfsvol"
+	"lukeshu.com/btrfs-tools/pkg/btrfsmisc"
+)
+
+func main() {
+	ctx := context.Background()
+	logger := logrus.New()
+	logger.SetLevel(logrus.TraceLevel)
+	ctx = dlog.WithLogger(ctx, dlog.WrapLogrus(logger))
+
+	grp := dgroup.NewGroup(ctx, dgroup.GroupConfig{
+		EnableSignalHandling: true,
+	})
+	grp.Go("main", func(ctx context.Context) error {
+		return Main(ctx, os.Args[1], os.Args[2:]...)
+	})
+	if err := grp.Wait(); err != nil {
+		fmt.Fprintf(os.Stderr, "%v: error: %v\n", os.Args[0], err)
+		os.Exit(1)
+	}
+}
+
+func Main(ctx context.Context, mountpoint string, imgfilenames ...string) (err error) {
+	maybeSetErr := func(_err error) {
+		if _err != nil && err == nil {
+			err = _err
+		}
+	}
+
+	fs, err := btrfsmisc.Open(os.O_RDONLY, imgfilenames...)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		maybeSetErr(fs.Close())
+	}()
+
+	fsAdapter := &FSAdapter{
+		fs: fs,
+	}
+
+	devname, err := filepath.Abs(imgfilenames[0])
+	if err != nil {
+		devname = imgfilenames[0]
+	}
+	mount, err := fuse.Mount(
+		mountpoint,
+		fuseutil.NewFileSystemServer(fsAdapter),
+		&fuse.MountConfig{
+			OpContext:   ctx,
+			ErrorLogger: dlog.StdLogger(ctx, dlog.LogLevelError),
+			DebugLogger: dlog.StdLogger(ctx, dlog.LogLevelDebug),
+
+			FSName:  devname,
+			Subtype: "btrfs",
+
+			ReadOnly: true,
+		})
+	if err != nil {
+		return err
+	}
+
+	mounted := uint32(1)
+	grp := dgroup.NewGroup(ctx, dgroup.GroupConfig{
+		ShutdownOnNonError: true,
+	})
+	grp.Go("send-unmount", func(ctx context.Context) error {
+		<-ctx.Done()
+		if atomic.LoadUint32(&mounted) == 0 {
+			return nil
+		}
+		return fuse.Unmount(os.Args[1])
+	})
+	grp.Go("recv-unmount", func(ctx context.Context) error {
+		ret := mount.Join(dcontext.HardContext(ctx))
+		atomic.StoreUint32(&mounted, 0)
+		return ret
+	})
+	return grp.Wait()
+}
+
+type FSAdapter struct {
+	fuseutil.NotImplementedFileSystem
+
+	fs *btrfs.FS
+
+	rootInodeOnce sync.Once
+	rootInodeVal  btrfs.ObjID
+	rootInodeErr  error
+
+	inode2treeMu sync.Mutex
+	inode2tree   map[btrfs.ObjID]btrfsvol.LogicalAddr
+}
+
+func (a *FSAdapter) getRootInode() (btrfs.ObjID, error) {
+	a.rootInodeOnce.Do(func() {
+		a.rootInodeVal, a.rootInodeErr = func() (btrfs.ObjID, error) {
+			sb, err := a.fs.Superblock()
+			if err != nil {
+				return 0, err
+			}
+
+			root, err := fs.TreeLookup(sb.Data.RootTree, btrfs.Key{
+				ObjectID: btrfs.FS_TREE_OBJECTID,
+				ItemType: btrfsitem.ROOT_ITEM_KEY,
+				Offset:   0,
+			})
+			if err != nil {
+				return 0, err
+			}
+			rootBody, ok := root.Body.(btrfsitem.Root)
+			if !ok {
+				return 0, fmt.Errorf("FS_TREE_ ROOT_ITEM has malformed body")
+			}
+			return rootBody.RootDirID, nil
+		}()
+	})
+	return a.rootInodeVal, a.rootInodeErr
+}
+
+func (a *FSAdapter) StatFS(_ context.Context, op *fuseops.StatFSOp) error {
+	// See linux.git/fs/btrfs/super.c:btrfs_statfs()
+	sb, err := a.fs.Superblock()
+	if err != nil {
+		return err
+	}
+
+	op.IoSize = sb.Data.SectorSize
+	op.BlockSize = sb.Data.SectorSize
+	op.Blocks = sb.Data.TotalBytes / uint64(sb.Data.SectorSize) // TODO: adjust for RAID type
+	//op.BlocksFree = TODO
+
+	// btrfs doesn't have a fixed number of inodes
+	op.Inodes = 0
+	op.InodesFree = 0
+
+	// jacobsa/fuse doesn't expose namelen, instead hard-coding it
+	// to 255.  Which is fine by us, because that's what it is for
+	// btrfs.
+
+	return nil
+}
+
+// func (a *FSAdapter) LookUpInode(_ context.Context, op *fuseops.LookUpInodeOp) error               {}
+
+func (a *FSAdapter) GetInodeAttributes(ctx context.Context, op *fuseops.GetInodeAttributesOp) error {
+	sb, err := a.fs.Superblock()
+	if err != nil {
+		return err
+	}
+
+	if op.Inode == fuseops.RootInodeID {
+		io.Inode, err = a.getRootInode()
+		if err != nil {
+			return err
+		}
+	}
+
+}
+
+// func (a *FSAdapter) ForgetInode(_ context.Context, op *fuseops.ForgetInodeOp) error               {}
+// func (a *FSAdapter) BatchForget(_ context.Context, op *fuseops.BatchForgetOp) error               {}
+// func (a *FSAdapter) OpenDir(_ context.Context, op *fuseops.OpenDirOp) error                       {}
+// func (a *FSAdapter) ReadDir(_ context.Context, op *fuseops.ReadDirOp) error                       {}
+// func (a *FSAdapter) ReleaseDirHandle(_ context.Context, op *fuseops.ReleaseDirHandleOp) error     {}
+// func (a *FSAdapter) OpenFile(_ context.Context, op *fuseops.OpenFileOp) error                     {}
+// func (a *FSAdapter) ReadFile(_ context.Context, op *fuseops.ReadFileOp) error                     {}
+// func (a *FSAdapter) ReleaseFileHandle(_ context.Context, op *fuseops.ReleaseFileHandleOp) error   {}
+// func (a *FSAdapter) ReadSymlink(_ context.Context, op *fuseops.ReadSymlinkOp) error               {}
+// func (a *FSAdapter) GetXattr(_ context.Context, op *fuseops.GetXattrOp) error                     {}
+// func (a *FSAdapter) ListXattr(_ context.Context, op *fuseops.ListXattrOp) error                   {}
+// func (a *FSAdapter) Destroy()                                                                {}