diff options
Diffstat (limited to 'pkg/sentry/vfs/vfs.go')
-rw-r--r-- | pkg/sentry/vfs/vfs.go | 268 |
1 files changed, 167 insertions, 101 deletions
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go index 58c7ad778..5bd756ea5 100644 --- a/pkg/sentry/vfs/vfs.go +++ b/pkg/sentry/vfs/vfs.go @@ -24,9 +24,9 @@ // Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry // VirtualFilesystem.filesystemsMu // EpollInstance.mu -// Inotify.mu -// Watches.mu -// Inotify.evMu +// Inotify.mu +// Watches.mu +// Inotify.evMu // VirtualFilesystem.fsTypesMu // // Locking Dentry.mu in multiple Dentries requires holding @@ -36,6 +36,7 @@ package vfs import ( "fmt" + "path" "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" @@ -122,7 +123,10 @@ type VirtualFilesystem struct { } // Init initializes a new VirtualFilesystem with no mounts or FilesystemTypes. -func (vfs *VirtualFilesystem) Init() error { +func (vfs *VirtualFilesystem) Init(ctx context.Context) error { + if vfs.mountpoints != nil { + panic("VFS already initialized") + } vfs.mountpoints = make(map[*Dentry]map[*Mount]struct{}) vfs.devices = make(map[devTuple]*registeredDevice) vfs.anonBlockDevMinorNext = 1 @@ -142,7 +146,7 @@ func (vfs *VirtualFilesystem) Init() error { devMinor: anonfsDevMinor, } anonfs.vfsfs.Init(vfs, &anonFilesystemType{}, &anonfs) - defer anonfs.vfsfs.DecRef() + defer anonfs.vfsfs.DecRef(ctx) anonMount, err := vfs.NewDisconnectedMount(&anonfs.vfsfs, nil, &MountOptions{}) if err != nil { // We should not be passing any MountOptions that would cause @@ -159,6 +163,8 @@ func (vfs *VirtualFilesystem) Init() error { // PathOperation is passed to VFS methods by pointer to reduce memory copying: // it's somewhat large and should never escape. (Options structs are passed by // pointer to VFS and FileDescription methods for the same reason.) +// +// +stateify savable type PathOperation struct { // Root is the VFS root. References on Root are borrowed from the provider // of the PathOperation. @@ -189,11 +195,11 @@ func (vfs *VirtualFilesystem) AccessAt(ctx context.Context, creds *auth.Credenti for { err := rp.mount.fs.impl.AccessAt(ctx, rp, creds, ats) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -211,11 +217,11 @@ func (vfs *VirtualFilesystem) GetDentryAt(ctx context.Context, creds *auth.Crede dentry: d, } rp.mount.IncRef() - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return vd, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return VirtualDentry{}, err } } @@ -233,7 +239,7 @@ func (vfs *VirtualFilesystem) getParentDirAndName(ctx context.Context, creds *au } rp.mount.IncRef() name := rp.Component() - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return parentVD, name, nil } if checkInvariants { @@ -241,8 +247,8 @@ func (vfs *VirtualFilesystem) getParentDirAndName(ctx context.Context, creds *au panic(fmt.Sprintf("%T.GetParentDentryAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return VirtualDentry{}, "", err } } @@ -257,14 +263,14 @@ func (vfs *VirtualFilesystem) LinkAt(ctx context.Context, creds *auth.Credential } if !newpop.Path.Begin.Ok() { - oldVD.DecRef() + oldVD.DecRef(ctx) if newpop.Path.Absolute { return syserror.EEXIST } return syserror.ENOENT } if newpop.FollowFinalSymlink { - oldVD.DecRef() + oldVD.DecRef(ctx) ctx.Warningf("VirtualFilesystem.LinkAt: file creation paths can't follow final symlink") return syserror.EINVAL } @@ -273,8 +279,8 @@ func (vfs *VirtualFilesystem) LinkAt(ctx context.Context, creds *auth.Credential for { err := rp.mount.fs.impl.LinkAt(ctx, rp, oldVD) if err == nil { - vfs.putResolvingPath(rp) - oldVD.DecRef() + vfs.putResolvingPath(ctx, rp) + oldVD.DecRef(ctx) return nil } if checkInvariants { @@ -282,9 +288,9 @@ func (vfs *VirtualFilesystem) LinkAt(ctx context.Context, creds *auth.Credential panic(fmt.Sprintf("%T.LinkAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) - oldVD.DecRef() + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) + oldVD.DecRef(ctx) return err } } @@ -293,6 +299,8 @@ func (vfs *VirtualFilesystem) LinkAt(ctx context.Context, creds *auth.Credential // MkdirAt creates a directory at the given path. func (vfs *VirtualFilesystem) MkdirAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *MkdirOptions) error { if !pop.Path.Begin.Ok() { + // pop.Path should not be empty in operations that create/delete files. + // This is consistent with mkdirat(dirfd, "", mode). if pop.Path.Absolute { return syserror.EEXIST } @@ -310,7 +318,7 @@ func (vfs *VirtualFilesystem) MkdirAt(ctx context.Context, creds *auth.Credentia for { err := rp.mount.fs.impl.MkdirAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } if checkInvariants { @@ -318,8 +326,8 @@ func (vfs *VirtualFilesystem) MkdirAt(ctx context.Context, creds *auth.Credentia panic(fmt.Sprintf("%T.MkdirAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -329,6 +337,8 @@ func (vfs *VirtualFilesystem) MkdirAt(ctx context.Context, creds *auth.Credentia // error from the syserror package. func (vfs *VirtualFilesystem) MknodAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *MknodOptions) error { if !pop.Path.Begin.Ok() { + // pop.Path should not be empty in operations that create/delete files. + // This is consistent with mknodat(dirfd, "", mode, dev). if pop.Path.Absolute { return syserror.EEXIST } @@ -343,7 +353,7 @@ func (vfs *VirtualFilesystem) MknodAt(ctx context.Context, creds *auth.Credentia for { err := rp.mount.fs.impl.MknodAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } if checkInvariants { @@ -351,8 +361,8 @@ func (vfs *VirtualFilesystem) MknodAt(ctx context.Context, creds *auth.Credentia panic(fmt.Sprintf("%T.MknodAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -405,31 +415,31 @@ func (vfs *VirtualFilesystem) OpenAt(ctx context.Context, creds *auth.Credential for { fd, err := rp.mount.fs.impl.OpenAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) if opts.FileExec { if fd.Mount().Flags.NoExec { - fd.DecRef() + fd.DecRef(ctx) return nil, syserror.EACCES } // Only a regular file can be executed. stat, err := fd.Stat(ctx, StatOptions{Mask: linux.STATX_TYPE}) if err != nil { - fd.DecRef() + fd.DecRef(ctx) return nil, err } if stat.Mask&linux.STATX_TYPE == 0 || stat.Mode&linux.S_IFMT != linux.S_IFREG { - fd.DecRef() + fd.DecRef(ctx) return nil, syserror.EACCES } } - fd.Dentry().InotifyWithParent(linux.IN_OPEN, 0, PathEvent) + fd.Dentry().InotifyWithParent(ctx, linux.IN_OPEN, 0, PathEvent) return fd, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return nil, err } } @@ -441,11 +451,11 @@ func (vfs *VirtualFilesystem) ReadlinkAt(ctx context.Context, creds *auth.Creden for { target, err := rp.mount.fs.impl.ReadlinkAt(ctx, rp) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return target, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return "", err } } @@ -469,19 +479,19 @@ func (vfs *VirtualFilesystem) RenameAt(ctx context.Context, creds *auth.Credenti return err } if oldName == "." || oldName == ".." { - oldParentVD.DecRef() + oldParentVD.DecRef(ctx) return syserror.EBUSY } if !newpop.Path.Begin.Ok() { - oldParentVD.DecRef() + oldParentVD.DecRef(ctx) if newpop.Path.Absolute { return syserror.EBUSY } return syserror.ENOENT } if newpop.FollowFinalSymlink { - oldParentVD.DecRef() + oldParentVD.DecRef(ctx) ctx.Warningf("VirtualFilesystem.RenameAt: destination path can't follow final symlink") return syserror.EINVAL } @@ -494,8 +504,8 @@ func (vfs *VirtualFilesystem) RenameAt(ctx context.Context, creds *auth.Credenti for { err := rp.mount.fs.impl.RenameAt(ctx, rp, oldParentVD, oldName, renameOpts) if err == nil { - vfs.putResolvingPath(rp) - oldParentVD.DecRef() + vfs.putResolvingPath(ctx, rp) + oldParentVD.DecRef(ctx) return nil } if checkInvariants { @@ -503,9 +513,9 @@ func (vfs *VirtualFilesystem) RenameAt(ctx context.Context, creds *auth.Credenti panic(fmt.Sprintf("%T.RenameAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) - oldParentVD.DecRef() + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) + oldParentVD.DecRef(ctx) return err } } @@ -514,6 +524,8 @@ func (vfs *VirtualFilesystem) RenameAt(ctx context.Context, creds *auth.Credenti // RmdirAt removes the directory at the given path. func (vfs *VirtualFilesystem) RmdirAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation) error { if !pop.Path.Begin.Ok() { + // pop.Path should not be empty in operations that create/delete files. + // This is consistent with unlinkat(dirfd, "", AT_REMOVEDIR). if pop.Path.Absolute { return syserror.EBUSY } @@ -528,7 +540,7 @@ func (vfs *VirtualFilesystem) RmdirAt(ctx context.Context, creds *auth.Credentia for { err := rp.mount.fs.impl.RmdirAt(ctx, rp) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } if checkInvariants { @@ -536,8 +548,8 @@ func (vfs *VirtualFilesystem) RmdirAt(ctx context.Context, creds *auth.Credentia panic(fmt.Sprintf("%T.RmdirAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -549,11 +561,11 @@ func (vfs *VirtualFilesystem) SetStatAt(ctx context.Context, creds *auth.Credent for { err := rp.mount.fs.impl.SetStatAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -565,11 +577,11 @@ func (vfs *VirtualFilesystem) StatAt(ctx context.Context, creds *auth.Credential for { stat, err := rp.mount.fs.impl.StatAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return stat, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return linux.Statx{}, err } } @@ -582,11 +594,11 @@ func (vfs *VirtualFilesystem) StatFSAt(ctx context.Context, creds *auth.Credenti for { statfs, err := rp.mount.fs.impl.StatFSAt(ctx, rp) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return statfs, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return linux.Statfs{}, err } } @@ -595,6 +607,8 @@ func (vfs *VirtualFilesystem) StatFSAt(ctx context.Context, creds *auth.Credenti // SymlinkAt creates a symbolic link at the given path with the given target. func (vfs *VirtualFilesystem) SymlinkAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, target string) error { if !pop.Path.Begin.Ok() { + // pop.Path should not be empty in operations that create/delete files. + // This is consistent with symlinkat(oldpath, newdirfd, ""). if pop.Path.Absolute { return syserror.EEXIST } @@ -609,7 +623,7 @@ func (vfs *VirtualFilesystem) SymlinkAt(ctx context.Context, creds *auth.Credent for { err := rp.mount.fs.impl.SymlinkAt(ctx, rp, target) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } if checkInvariants { @@ -617,8 +631,8 @@ func (vfs *VirtualFilesystem) SymlinkAt(ctx context.Context, creds *auth.Credent panic(fmt.Sprintf("%T.SymlinkAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -627,6 +641,8 @@ func (vfs *VirtualFilesystem) SymlinkAt(ctx context.Context, creds *auth.Credent // UnlinkAt deletes the non-directory file at the given path. func (vfs *VirtualFilesystem) UnlinkAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation) error { if !pop.Path.Begin.Ok() { + // pop.Path should not be empty in operations that create/delete files. + // This is consistent with unlinkat(dirfd, "", 0). if pop.Path.Absolute { return syserror.EBUSY } @@ -641,7 +657,7 @@ func (vfs *VirtualFilesystem) UnlinkAt(ctx context.Context, creds *auth.Credenti for { err := rp.mount.fs.impl.UnlinkAt(ctx, rp) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } if checkInvariants { @@ -649,8 +665,8 @@ func (vfs *VirtualFilesystem) UnlinkAt(ctx context.Context, creds *auth.Credenti panic(fmt.Sprintf("%T.UnlinkAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -658,17 +674,11 @@ func (vfs *VirtualFilesystem) UnlinkAt(ctx context.Context, creds *auth.Credenti // BoundEndpointAt gets the bound endpoint at the given path, if one exists. func (vfs *VirtualFilesystem) BoundEndpointAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *BoundEndpointOptions) (transport.BoundEndpoint, error) { - if !pop.Path.Begin.Ok() { - if pop.Path.Absolute { - return nil, syserror.ECONNREFUSED - } - return nil, syserror.ENOENT - } rp := vfs.getResolvingPath(creds, pop) for { bep, err := rp.mount.fs.impl.BoundEndpointAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return bep, nil } if checkInvariants { @@ -676,21 +686,21 @@ func (vfs *VirtualFilesystem) BoundEndpointAt(ctx context.Context, creds *auth.C panic(fmt.Sprintf("%T.BoundEndpointAt() consumed all path components and returned %v", rp.mount.fs.impl, err)) } } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return nil, err } } } -// ListxattrAt returns all extended attribute names for the file at the given +// ListXattrAt returns all extended attribute names for the file at the given // path. -func (vfs *VirtualFilesystem) ListxattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, size uint64) ([]string, error) { +func (vfs *VirtualFilesystem) ListXattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, size uint64) ([]string, error) { rp := vfs.getResolvingPath(creds, pop) for { - names, err := rp.mount.fs.impl.ListxattrAt(ctx, rp, size) + names, err := rp.mount.fs.impl.ListXattrAt(ctx, rp, size) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return names, nil } if err == syserror.ENOTSUP { @@ -698,61 +708,61 @@ func (vfs *VirtualFilesystem) ListxattrAt(ctx context.Context, creds *auth.Crede // fs/xattr.c:vfs_listxattr() falls back to allowing the security // subsystem to return security extended attributes, which by // default don't exist. - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return nil, err } } } -// GetxattrAt returns the value associated with the given extended attribute +// GetXattrAt returns the value associated with the given extended attribute // for the file at the given path. -func (vfs *VirtualFilesystem) GetxattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *GetxattrOptions) (string, error) { +func (vfs *VirtualFilesystem) GetXattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *GetXattrOptions) (string, error) { rp := vfs.getResolvingPath(creds, pop) for { - val, err := rp.mount.fs.impl.GetxattrAt(ctx, rp, *opts) + val, err := rp.mount.fs.impl.GetXattrAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return val, nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return "", err } } } -// SetxattrAt changes the value associated with the given extended attribute +// SetXattrAt changes the value associated with the given extended attribute // for the file at the given path. -func (vfs *VirtualFilesystem) SetxattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *SetxattrOptions) error { +func (vfs *VirtualFilesystem) SetXattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, opts *SetXattrOptions) error { rp := vfs.getResolvingPath(creds, pop) for { - err := rp.mount.fs.impl.SetxattrAt(ctx, rp, *opts) + err := rp.mount.fs.impl.SetXattrAt(ctx, rp, *opts) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } } -// RemovexattrAt removes the given extended attribute from the file at rp. -func (vfs *VirtualFilesystem) RemovexattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, name string) error { +// RemoveXattrAt removes the given extended attribute from the file at rp. +func (vfs *VirtualFilesystem) RemoveXattrAt(ctx context.Context, creds *auth.Credentials, pop *PathOperation, name string) error { rp := vfs.getResolvingPath(creds, pop) for { - err := rp.mount.fs.impl.RemovexattrAt(ctx, rp, name) + err := rp.mount.fs.impl.RemoveXattrAt(ctx, rp, name) if err == nil { - vfs.putResolvingPath(rp) + vfs.putResolvingPath(ctx, rp) return nil } - if !rp.handleError(err) { - vfs.putResolvingPath(rp) + if !rp.handleError(ctx, err) { + vfs.putResolvingPath(ctx, rp) return err } } @@ -774,11 +784,67 @@ func (vfs *VirtualFilesystem) SyncAllFilesystems(ctx context.Context) error { if err := fs.impl.Sync(ctx); err != nil && retErr == nil { retErr = err } - fs.DecRef() + fs.DecRef(ctx) } return retErr } +// MkdirAllAt recursively creates non-existent directories on the given path +// (including the last component). +func (vfs *VirtualFilesystem) MkdirAllAt(ctx context.Context, currentPath string, root VirtualDentry, creds *auth.Credentials, mkdirOpts *MkdirOptions) error { + pop := &PathOperation{ + Root: root, + Start: root, + Path: fspath.Parse(currentPath), + } + stat, err := vfs.StatAt(ctx, creds, pop, &StatOptions{Mask: linux.STATX_TYPE}) + switch err { + case nil: + if stat.Mask&linux.STATX_TYPE == 0 || stat.Mode&linux.FileTypeMask != linux.ModeDirectory { + return syserror.ENOTDIR + } + // Directory already exists. + return nil + case syserror.ENOENT: + // Expected, we will create the dir. + default: + return fmt.Errorf("stat failed for %q during directory creation: %w", currentPath, err) + } + + // Recurse to ensure parent is created and then create the final directory. + if err := vfs.MkdirAllAt(ctx, path.Dir(currentPath), root, creds, mkdirOpts); err != nil { + return err + } + if err := vfs.MkdirAt(ctx, creds, pop, mkdirOpts); err != nil { + return fmt.Errorf("failed to create directory %q: %w", currentPath, err) + } + return nil +} + +// MakeSyntheticMountpoint creates parent directories of target if they do not +// exist and attempts to create a directory for the mountpoint. If a +// non-directory file already exists there then we allow it. +func (vfs *VirtualFilesystem) MakeSyntheticMountpoint(ctx context.Context, target string, root VirtualDentry, creds *auth.Credentials) error { + mkdirOpts := &MkdirOptions{Mode: 0777, ForSyntheticMountpoint: true} + + // Make sure the parent directory of target exists. + if err := vfs.MkdirAllAt(ctx, path.Dir(target), root, creds, mkdirOpts); err != nil { + return fmt.Errorf("failed to create parent directory of mountpoint %q: %w", target, err) + } + + // Attempt to mkdir the final component. If a file (of any type) exists + // then we let allow mounting on top of that because we do not require the + // target to be an existing directory, unlike Linux mount(2). + if err := vfs.MkdirAt(ctx, creds, &PathOperation{ + Root: root, + Start: root, + Path: fspath.Parse(target), + }, mkdirOpts); err != nil && err != syserror.EEXIST { + return fmt.Errorf("failed to create mountpoint %q: %w", target, err) + } + return nil +} + // A VirtualDentry represents a node in a VFS tree, by combining a Dentry // (which represents a node in a Filesystem's tree) and a Mount (which // represents the Filesystem's position in a VFS mount tree). @@ -828,9 +894,9 @@ func (vd VirtualDentry) IncRef() { // DecRef decrements the reference counts on the Mount and Dentry represented // by vd. -func (vd VirtualDentry) DecRef() { - vd.dentry.DecRef() - vd.mount.DecRef() +func (vd VirtualDentry) DecRef(ctx context.Context) { + vd.dentry.DecRef(ctx) + vd.mount.DecRef(ctx) } // Mount returns the Mount associated with vd. It does not take a reference on |