UKFS(3) | Library Functions Manual | UKFS(3) |
ukfs
—
#include <rump/ukfs.h>
ukfs
library provides direct access to file systems
without having to specially mount a file system. Therefore, accessing a file
system through ukfs
requires no special kernel support
apart from standard POSIX functionality. As ukfs
is
built upon rump(3) kernels, all
kernel file systems which are supported by rump kernels are available. It
allows to write utilities for accessing file systems without having to
duplicate file system internals knowledge already present in kernel file
system drivers.
ukfs
provides a high-level pathname based
interface for accessing file systems. If a lower level interface it desired,
rump(3) kernels should be used
directly. However, much like system calls, the interfaces of
ukfs
are self-contained and require no tracking and
release of resources. The only exception is the file system handle
struct ukfs which should be released after use.
ukfs_init
()ukfs_modload
(const char
*fname)ukfs_modload_dir
(const char
*dirname)ukfs_vfstypes
(char *buf,
size_t buflen)ukfs_mount
(const char
*vfsname, const char *devpath,
const char *mountpath, int
mntflags, void *arg, size_t
alen)ukfs_mount_disk
(const char
*vfsname, const char *devpath,
int partition, const char
*mountpath, int mntflags, void
*arg, size_t alen)ukfs_release
(struct ukfs
*ukfs, int flags)ukfs_init
() initializes the library and
must be called once per process using ukfs
.
ukfs_modload
() is used at runtime to
dynamically load a library which contains a file system module. For this to
succeed, the rump(3) kernel and
the module targetted must be compiled with compatible kernel versions and
the application must be dynamically linked. Additionally, since this routine
does not handle dependencies, all the dependencies of the library must be
loaded beforehand. The routine returns -1 for fatal error, 0 for dependency
failure and 1 for success.
ukfs_modload_dir
() loads all
rump(3) kernel file system
components in directory dirname. It looks for
libraries which begin with librumpfs_ and end in
.so. The routine tries to handle dependencies by
retrying to load libraries which failed due to dependencies.
ukfs_modload_dir
() returns the number of vfs modules
loaded or sets errno and returns -1 in case of a fatal error in directory
searching. In case a fatal error occurs after some modules have already been
loaded, the number of loaded module is returned. Fatal errors in loading the
modules themselves are ignored and ukfs_modload
()
should be used directly if finegrained error reporting is desired.
It should be noted that the above routines affect the whole
process, not just a specific instance of ukfs
. It is
preferable to call them from only one thread, as the underlying dynamic
library interfaces may not be threadsafe.
ukfs_vfstypes
() queries the available file
system types and returns a nul-terminated list of types separated by spaces
in buf. The format of the list is equivalent to the
one returned by sysctl(3) on
the name vfs.generic.fstypes. The function returns
the length of the string without the trailing nul or -1 for error. Notably,
the return value 0 means there are no file systems available. If there is
not enough room in the caller's buffer for all file system types, as many as
fit will be returned.
ukfs_mount
() initializes a file system
image. The handle resulting from the operation is passed to all other
routines and identifies the instance of the mount analoguous to what a
pathname specifies in a normally mounted file system. The parameters are the
following:
MOUNT_FFS
.UKFS_DEFAULTMP
is the correct path.MNT_RDONLY
. In addition to generic
parameters, file system specific parameters such as
MNT_LOG
(ffs) may be passed here.The ukfs_mount_disk
() function must be
used to mount disk-based file systems. It takes the same arguments as
ukfs_mount
(), except for an additional argument
signifying the partition number. If the image
devpath contains a disklabel, this value specifies the
number of the partition within the image used as the file system backend. If
devpath does not contain a disklabel, the value
UKFS_PARTITION_NONE
must be used to signal that the
file system backend is the entire image.
ukfs_release
() unmounts the file system
and releases the resources associated with ukfs. The
return value signals the return value of the unmount operation. If non-zero,
ukfs will continue to remain valid. The possible
values for flags are:
UKFS_RELFLAG_NOUNMOUNT
UKFS_RELFLAG_FORCE
ukfs_chdir
()) will be ignored. Release always
succeeds.ukfs_chdir
(struct ukfs
*ukfs, const char *path)ukfs_getdents
(struct ukfs
*ukfs, const char *dirname,
off_t *off, uint8_t *buf,
size_t bufsize)ukfs_read
(struct ukfs *ukfs,
const char *filename, off_t
off, uint8_t *buf, size_t
bufsize)ukfs_write
(struct ukfs
*ukfs, const char *filename,
off_t off, uint8_t *buf,
size_t bufsize)ukfs_create
(struct ukfs
*ukfs, const char *filename,
mode_t mode)ukfs_mknod
(struct ukfs
*ukfs, const char *path,
mode_t mode, dev_t dev)ukfs_mkfifo
(struct ukfs
*ukfs, const char *path,
mode_t mode)ukfs_mkdir
(struct ukfs
*ukfs, const char *filename,
mode_t mode)ukfs_remove
(struct ukfs
*ukfs, const char *filename)ukfs_rmdir
(struct ukfs
*ukfs, const char *filename)ukfs_link
(struct ukfs *ukfs,
const char *filename, const char
*f_create)ukfs_symlink
(struct ukfs
*ukfs, const char *filename,
const char *linkname)ukfs_readlink
(struct ukfs
*ukfs, const char *filename,
char *linkbuf, size_t
buflen)ukfs_rename
(struct ukfs
*ukfs, const char *from, const
char *to)ukfs_stat
(struct ukfs *ukfs,
const char *filename, struct stat
*file_stat)ukfs_lstat
(struct ukfs
*ukfs, const char *filename,
struct stat *file_stat)ukfs_chmod
(struct ukfs
*ukfs, const char *filename,
mode_t mode)ukfs_lchmod
(struct ukfs
*ukfs, const char *filename,
mode_t mode)ukfs_chown
(struct ukfs
*ukfs, const char *filename,
uid_t uid, gid_t gid)ukfs_lchown
(struct ukfs
*ukfs, const char *filename,
uid_t uid, gid_t gid)ukfs_chflags
(struct ukfs
*ukfs, const char *filename,
u_long flags)ukfs_lchflags
(struct ukfs
*ukfs, const char *filename,
u_long flags)ukfs_utimes
(struct ukfs
*ukfs, const char *filename,
const struct timeval *tptr)ukfs_lutimes
(struct ukfs
*ukfs, const char *filename,
const struct timeval *tptr)The above routines operate like their system call counterparts and the system call manual pages without the ukfs_ prefix should be referred to for further information on the parameters.
The only call which modifies ukfs state is
ukfs_chdir
(). It works like
chdir(2) in the sense that it
affects the interpretation of relative paths. If succesful, all relative
pathnames will be resolved starting from the current directory. Currently
the call affects all accesses to that particular ukfs,
but it might be later changed to be thread private.
ukfs_util_builddirs
(struct ukfs
*ukfs, const char *pathname,
mode_t mode)Builds a directory hierarchy. Unlike mkdir, the pathname argument may contain multiple levels of hierarchy. It is not considered an error if any of the directories specified exist already.
ukfs
first appeared in NetBSD
5.0.
ukfs
was an early attempt at an interface for kernel
file systems running in userspace.
March 12, 2018 | NetBSD 9.2 |