Trait Filesystem 

pub trait Filesystem {
    // Provided methods
    fn init(&self, req: RequestInfo, config: &mut KernelConfig) -> ResultEmpty { ... }
    fn destroy(&self) { ... }
    fn getattr(
        &self,
        req: RequestInfo,
        path: &EntryRef,
        fh: Option<u64>,
    ) -> ResultEntry { ... }
    fn chmod(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: Option<u64>,
        mode: u32,
    ) -> ResultEmpty { ... }
    fn chown(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: Option<u64>,
        uid: Option<u32>,
        gid: Option<u32>,
    ) -> ResultEmpty { ... }
    fn truncate(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: Option<u64>,
        size: u64,
    ) -> ResultEmpty { ... }
    fn utimens(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: Option<u64>,
        atime: Option<SystemTime>,
        mtime: Option<SystemTime>,
    ) -> ResultEmpty { ... }
    fn utimens_macos(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: Option<u64>,
        crtime: Option<SystemTime>,
        chgtime: Option<SystemTime>,
        bkuptime: Option<SystemTime>,
        flags: Option<u32>,
    ) -> ResultEmpty { ... }
    fn readlink(&self, req: RequestInfo, path: &ResolvedPath) -> ResultData { ... }
    fn mknod(
        &self,
        req: RequestInfo,
        entry: &EntryName,
        mode: u32,
        rdev: u32,
    ) -> ResultEntry { ... }
    fn mkdir(
        &self,
        req: RequestInfo,
        entry: &EntryName,
        mode: u32,
    ) -> ResultEntry { ... }
    fn unlink(&self, req: RequestInfo, entry: &EntryName) -> ResultEmpty { ... }
    fn rmdir(&self, req: RequestInfo, entry: &EntryName) -> ResultEmpty { ... }
    fn symlink(
        &self,
        req: RequestInfo,
        entry: &EntryName,
        target: &Path,
    ) -> ResultEntry { ... }
    fn rename(
        &self,
        req: RequestInfo,
        entry: &EntryName,
        new_entry: &EntryName,
    ) -> ResultEmpty { ... }
    fn link(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        new_entry: &EntryName,
    ) -> ResultEntry { ... }
    fn open(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        flags: u32,
    ) -> ResultOpen { ... }
    fn read(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        offset: u64,
        size: u32,
        callback: impl FnOnce(ResultSlice<'_>) -> CallbackResult,
    ) -> CallbackResult { ... }
    fn write(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        offset: u64,
        data: Vec<u8>,
        flags: u32,
    ) -> ResultWrite { ... }
    fn flush(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        lock_owner: u64,
    ) -> ResultEmpty { ... }
    fn release(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        flags: u32,
        lock_owner: u64,
        flush: bool,
    ) -> ResultEmpty { ... }
    fn fsync(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        datasync: bool,
    ) -> ResultEmpty { ... }
    fn opendir(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        flags: u32,
    ) -> ResultOpen { ... }
    fn readdir(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
    ) -> ResultReaddir { ... }
    fn releasedir(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        flags: u32,
    ) -> ResultEmpty { ... }
    fn fsyncdir(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        fh: u64,
        datasync: bool,
    ) -> ResultEmpty { ... }
    fn statfs(&self, req: RequestInfo, path: &ResolvedPath) -> ResultStatfs { ... }
    fn setxattr(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        name: &OsStr,
        value: &[u8],
        flags: u32,
        position: u32,
    ) -> ResultEmpty { ... }
    fn getxattr(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        name: &OsStr,
        size: u32,
    ) -> ResultXattr { ... }
    fn listxattr(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        size: u32,
    ) -> ResultXattr { ... }
    fn removexattr(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        name: &OsStr,
    ) -> ResultEmpty { ... }
    fn access(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        mask: u32,
    ) -> ResultEmpty { ... }
    fn create(
        &self,
        req: RequestInfo,
        path: &ResolvedPath,
        mode: u32,
        flags: u32,
    ) -> ResultCreate { ... }
}

This trait must be implemented to implement a filesystem with FuserNG.

Methods have default ENOSYS implementations, so a filesystem can implement only the operations it supports.

use std::io;
use std::time::{Duration, SystemTime};

use fuser_ng::{EntryRef, FileAttr, FileType, Filesystem, RequestInfo, ResultEntry};

struct RootOnly;

impl Filesystem for RootOnly {
    fn getattr(&self, _req: RequestInfo, path: &EntryRef, _fh: Option<u64>) -> ResultEntry {
        if path.full_path() != std::path::Path::new("/") {
            return Err(io::Error::from_raw_os_error(libc::ENOENT));
        }

        let now = SystemTime::now();

        Ok((
            Duration::from_secs(1),
            FileAttr {
                size: 0,
                blocks: 0,
                atime: now,
                mtime: now,
                ctime: now,
                crtime: now,
                kind: FileType::Directory,
                perm: 0o755,
                nlink: 2,
                uid: 0,
                gid: 0,
                rdev: 0,
                blksize: 512,
                flags: 0,
            },
        ))
    }
}

Provided Methods

fn init(&self, req: RequestInfo, config: &mut KernelConfig) -> ResultEmpty

Called on mount, before any other function.

fn destroy(&self)

Called on filesystem unmount.

fn getattr( &self, req: RequestInfo, path: &EntryRef, fh: Option<u64>, ) -> ResultEntry

Get the attributes of a filesystem entry.

• fh: a file handle if this is called on an open file.

fn chmod( &self, req: RequestInfo, path: &ResolvedPath, fh: Option<u64>, mode: u32, ) -> ResultEmpty

Change the mode of a filesystem entry.

• fh: a file handle if this is called on an open file.
• mode: the mode to change the file to.

fn chown( &self, req: RequestInfo, path: &ResolvedPath, fh: Option<u64>, uid: Option<u32>, gid: Option<u32>, ) -> ResultEmpty

Change the owner UID and/or group GID of a filesystem entry.

• fh: a file handle if this is called on an open file.
• uid: user ID to change the file’s owner to. If None, leave the UID unchanged.
• gid: group ID to change the file’s group to. If None, leave the GID unchanged.

fn truncate( &self, req: RequestInfo, path: &ResolvedPath, fh: Option<u64>, size: u64, ) -> ResultEmpty

Set the length of a file.

• fh: a file handle if this is called on an open file.
• size: size in bytes to set as the file’s length.

fn utimens( &self, req: RequestInfo, path: &ResolvedPath, fh: Option<u64>, atime: Option<SystemTime>, mtime: Option<SystemTime>, ) -> ResultEmpty

Set timestamps of a filesystem entry.

• fh: a file handle if this is called on an open file.
• atime: the time of last access.
• mtime: the time of last modification.

fn utimens_macos( &self, req: RequestInfo, path: &ResolvedPath, fh: Option<u64>, crtime: Option<SystemTime>, chgtime: Option<SystemTime>, bkuptime: Option<SystemTime>, flags: Option<u32>, ) -> ResultEmpty

Set timestamps of a filesystem entry (with extra options only used on MacOS).

fn readlink(&self, req: RequestInfo, path: &ResolvedPath) -> ResultData

Read a symbolic link.

fn mknod( &self, req: RequestInfo, entry: &EntryName, mode: u32, rdev: u32, ) -> ResultEntry

Create a special file.

• parent: path to the directory to make the entry under.
• name: name of the entry.
• mode: mode for the new entry.
• rdev: if mode has the bits S_IFCHR or S_IFBLK set, this is the major and minor numbers for the device file. Otherwise it should be ignored.

fn mkdir(&self, req: RequestInfo, entry: &EntryName, mode: u32) -> ResultEntry

Create a directory.

• parent: path to the directory to make the directory under.
• name: name of the directory.
• mode: permissions for the new directory.

fn unlink(&self, req: RequestInfo, entry: &EntryName) -> ResultEmpty

Remove a file.

• parent: path to the directory containing the file to delete.
• name: name of the file to delete.

fn rmdir(&self, req: RequestInfo, entry: &EntryName) -> ResultEmpty

Remove a directory.

• parent: path to the directory containing the directory to delete.
• name: name of the directory to delete.

fn symlink( &self, req: RequestInfo, entry: &EntryName, target: &Path, ) -> ResultEntry

Create a symbolic link.

• parent: path to the directory to make the link in.
• name: name of the symbolic link.
• target: path (may be relative or absolute) to the target of the link.

fn rename( &self, req: RequestInfo, entry: &EntryName, new_entry: &EntryName, ) -> ResultEmpty

Rename a filesystem entry.

• parent: path to the directory containing the existing entry.
• name: name of the existing entry.
• newparent: path to the directory it should be renamed into (may be the same as parent).
• newname: name of the new entry.

fn link( &self, req: RequestInfo, path: &ResolvedPath, new_entry: &EntryName, ) -> ResultEntry

Create a hard link.

• path: path to an existing file.
• newparent: path to the directory for the new link.
• newname: name for the new link.

fn open(&self, req: RequestInfo, path: &ResolvedPath, flags: u32) -> ResultOpen

Open a file.

• path: path to the file.
• flags: one of O_RDONLY, O_WRONLY, or O_RDWR, plus maybe additional flags.

Return a tuple of (file handle, flags). The file handle will be passed to any subsequent calls that operate on the file, and can be any value you choose, though it should allow your filesystem to identify the file opened even without any path info.

fn read( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, offset: u64, size: u32, callback: impl FnOnce(ResultSlice<'_>) -> CallbackResult, ) -> CallbackResult

Read from a file.

Note that it is not an error for this call to request to read past the end of the file, and you should only return data up to the end of the file (i.e. the number of bytes returned will be fewer than requested; possibly even zero). Do not extend the file in this case.

• path: path to the file.
• fh: file handle returned from the open call.
• offset: offset into the file to start reading.
• size: number of bytes to read.
• callback: a callback that must be invoked to return the result of the operation: either the result data as a slice, or an error code.

Return the return value from the callback function.

fn write( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, offset: u64, data: Vec<u8>, flags: u32, ) -> ResultWrite

Write to a file.

• path: path to the file.
• fh: file handle returned from the open call.
• offset: offset into the file to start writing.
• data: the data to write
• flags:

Return the number of bytes written.

fn flush( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, lock_owner: u64, ) -> ResultEmpty

Called each time a program calls close on an open file.

Note that because file descriptors can be duplicated (by dup, dup2, fork) this may be called multiple times for a given file handle. The main use of this function is if the filesystem would like to return an error to the close call. Note that most programs ignore the return value of close, though.

• path: path to the file.
• fh: file handle returned from the open call.
• lock_owner: if the filesystem supports locking (setlk, getlk), remove all locks belonging to this lock owner.

fn release( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, flags: u32, lock_owner: u64, flush: bool, ) -> ResultEmpty

Called when an open file is closed.

There will be one of these for each open call. After release, no more calls will be made with the given file handle.

• path: path to the file.
• fh: file handle returned from the open call.
• flags: the flags passed when the file was opened.
• lock_owner: if the filesystem supports locking (setlk, getlk), remove all locks belonging to this lock owner.
• flush: whether pending data must be flushed or not.

fn fsync( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, datasync: bool, ) -> ResultEmpty

Write out any pending changes of a file.

When this returns, data should be written to persistent storage.

• path: path to the file.
• fh: file handle returned from the open call.
• datasync: if false, also write metadata, otherwise just write file data.

fn opendir( &self, req: RequestInfo, path: &ResolvedPath, flags: u32, ) -> ResultOpen

Open a directory.

Analogous to the opend call.

• path: path to the directory.
• flags: file access flags. Will contain O_DIRECTORY at least.

Return a tuple of (file handle, flags). The file handle will be passed to any subsequent calls that operate on the directory, and can be any value you choose, though it should allow your filesystem to identify the directory opened even without any path info.

fn readdir( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, ) -> ResultReaddir

Get the entries of a directory.

• path: path to the directory.
• fh: file handle returned from the opendir call.

Return all the entries of the directory.

fn releasedir( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, flags: u32, ) -> ResultEmpty

Close an open directory.

This will be called exactly once for each opendir call.

• path: path to the directory.
• fh: file handle returned from the opendir call.
• flags: the file access flags passed to the opendir call.

fn fsyncdir( &self, req: RequestInfo, path: &ResolvedPath, fh: u64, datasync: bool, ) -> ResultEmpty

Write out any pending changes to a directory.

Analogous to the fsync call.

fn statfs(&self, req: RequestInfo, path: &ResolvedPath) -> ResultStatfs

Get filesystem statistics.

• path: path to some folder in the filesystem.

See the Statfs struct for more details.

fn setxattr( &self, req: RequestInfo, path: &ResolvedPath, name: &OsStr, value: &[u8], flags: u32, position: u32, ) -> ResultEmpty

Set a file extended attribute.

• path: path to the file.
• name: attribute name.
• value: the data to set the value to.
• flags: can be either XATTR_CREATE or XATTR_REPLACE.
• position: offset into the attribute value to write data.

fn getxattr( &self, req: RequestInfo, path: &ResolvedPath, name: &OsStr, size: u32, ) -> ResultXattr

Get a file extended attribute.

• path: path to the file
• name: attribute name.
• size: the maximum number of bytes to read.

If size is 0, return Xattr::Size(n) where n is the size of the attribute data. Otherwise, return Xattr::Data(data) with the requested data.

fn listxattr( &self, req: RequestInfo, path: &ResolvedPath, size: u32, ) -> ResultXattr

List extended attributes for a file.

• path: path to the file.
• size: maximum number of bytes to return.

If size is 0, return Xattr::Size(n) where n is the size required for the list of attribute names. Otherwise, return Xattr::Data(data) where data is all the null-terminated attribute names.

fn removexattr( &self, req: RequestInfo, path: &ResolvedPath, name: &OsStr, ) -> ResultEmpty

Remove an extended attribute for a file.

• path: path to the file.
• name: name of the attribute to remove.

fn access( &self, req: RequestInfo, path: &ResolvedPath, mask: u32, ) -> ResultEmpty

Check for access to a file.

• path: path to the file.
• mask: mode bits to check for access to.

Return Ok(()) if all requested permissions are allowed, otherwise return Err(EACCES) or other error code as appropriate (e.g. ENOENT if the file doesn’t exist).

fn create( &self, req: RequestInfo, path: &ResolvedPath, mode: u32, flags: u32, ) -> ResultCreate

Create and open a new file.

• parent: path to the directory to create the file in.
• name: name of the file to be created.
• mode: the mode to set on the new file.
• flags: flags like would be passed to open.

Return a CreatedEntry (which contains the new file’s attributes as well as a file handle – see documentation on open for more info on that).

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors