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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() {}
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