NAME
path_to_handle, path_to_fshandle, fd_to_handle, handle_to_fshandle,
open_by_handle, readlink_by_handle, attr_multi_by_handle,
attr_list_by_handle, fssetdm_by_handle, free_handle,
getparents_by_handle, getparentpaths_by_handle - file handle operations
C SYNOPSIS
#include <sys/types.h>
#include <xfs/handle.h>
int path_to_handle(char *path, void **hanp, size_t *hlen);
int path_to_fshandle(char *path, void **hanp, size_t *hlen);
int fd_to_handle(int fd, void **hanp, size_t *hlen);
int handle_to_fshandle(void *hanp, size_t hlen, void **fshanp, size_t
*fshlen);
int open_by_handle(void *hanp, size_t hlen, int oflag);
int readlink_by_handle(void *hanp, size_t hlen, void *buf, size_t bs);
int attr_multi_by_handle(void *hanp, size_t hlen, void *buf, int
rtrvcnt, int flags);
int attr_list_by_handle(void *hanp, size_t hlen, char *buf, size_t
bufsiz, int flags, struct attrlist_cursor *cursor);
int fssetdm_by_handle(void *hanp, size_t hlen, struct fsdmidata
*fssetdm);
void free_handle(void *hanp, size_t hlen);
int getparents_by_handle(void *hanp, size_t hlen, parent_t *buf, size_t
bufsiz, parent_cursor_t *cursor, unsigned int *count, unsigned
int *more);
int getparentpaths_by_handle(void *hanp, size_t hlen, parent_t *buf,
size_t bufsiz, parent_cursor_t *cursor, unsigned int *count,
unsigned int *more);
DESCRIPTION
These functions provide a way to perform certain filesystem operations
without using a file descriptor to access filesystem objects. They are
intended for use by a limited set of system utilities such as backup
programs. They are supported only by the XFS filesystem. Link with the
libhandle library to access these functions.
A handle, hanp, uniquely identifies a filesystem object or an entire
filesystem. There is one and only one handle per filesystem or
filesystem object. Handles consist of some number of bytes. The size
of a handle (i.e. the number of bytes comprising it) varies by the type
of handle and may vary for different objects of the same type. The
content of a handle is opaque to applications. Since handle sizes vary
and their contents are opaque, handles are described by two quantities,
a pointer (hanp) and a size (hlen). The size, hlen, indicates the
number of bytes in the handle which are pointed to by the pointer.
The path_to_handle() function returns the handle for the object given
by the path argument. If the final component of the path name is a
symbolic link, the handle returned is that of the link itself.
The path_to_fshandle() function returns the handle for the filesystem
in which the object given by the path argument resides.
The fd_to_handle() function returns the handle for the object
referenced by the fd argument, which must be a valid file descriptor.
The handle_to_fshandle() function returns the handle for the filesystem
in which the object referenced by the handle given by the hanp and hlen
arguments resides.
The open_by_handle() function opens a file descriptor for the object
referenced by a handle. It is analogous and identical to open(2) with
the exception of accepting handles instead of path names.
The readlink_by_handle() function returns the contents of a symbolic
link referenced by a handle.
The attr_multi_by_handle() function manipulates multiple user
attributes on a filesystem object. It is analogous and identical to
attr_multif(3) except that a handle is specified instead of a file
descriptor.
The attr_list_by_handle() function returns the names of the user
attributes of a filesystem object. It is analogous and identical to
attr_listf(3) except that a handle is specified instead of a file
descriptor.
The fssetdm_by_handle() function sets the di_dmevmask and di_dmstate
fields in an XFS on-disk inode. It is analogous to the XFS_IOC_FSSETDM
xfsctl(3) command, except that a handle is specified instead of a file.
The free_handle() function frees the storage allocated for handles
returned by the following functions: path_to_handle(),
path_to_fshandle(), fd_to_handle(), and handle_to_fshandle().
The getparents_by_handle() function returns an array of parent_t
structures for each hardlink to the inode represented by the given
handle. The parent structure encodes the parent inode number,
generation number and the basename of the link. This function is not
operational on Linux.
The getparentpaths_by_handle() function is identical to the
getparents_by_handle() function except that instead of returning the
basename it returns the path of the link up to the mount point. This
function is also not operational on Linux.
RETURN VALUE
The function free_handle() has no failure indication. The other
functions return the value 0 to the calling process if they succeed;
otherwise, they return the value -1 and set errno to indicate the
error.
ERRORS
EACCES Search permission was denied for a component of path.
EBADF fd is not a valid and open file descriptor.
EFAULT An argument pointed to an invalid address.
EINVAL path is in a filesystem that does not support these functions.
ELOOP Too many symbolic links were encountered in translating the path
name.
ENAMETOOLONG
A component of path or the entire length of path exceeds
filesystem limits.
ENOENT A component of path does not exist.
EPERM The caller does not have sufficient privileges.
SEE ALSO
open(2), readlink(2), attr_multi(3), attr_list(3), xfsctl(3), xfs(5).
HANDLE(3)