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authorKonstantin Belousov <kib@FreeBSD.org>2018-12-07 15:17:29 +0000
committerKonstantin Belousov <kib@FreeBSD.org>2018-12-07 15:17:29 +0000
commitd1fd400a8048db0a958b0f441ae542fb5e9e16e7 (patch)
tree1a5af3dd642ba46c0e6de52d6d890c2cd80f1cfc /lib/libc/sys/fhlink.2
parentb1fbffe73cd7dca2c79e31bfc48a242b41d1020b (diff)
downloadsrc-d1fd400a8048db0a958b0f441ae542fb5e9e16e7.tar.gz
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Add new file handle system calls.
Namely, getfhat(2), fhlink(2), fhlinkat(2), fhreadlink(2). The syscalls are provided for a NFS userspace server (nfs-ganesha). Submitted by: Jack Halford <jack@gandi.net> Sponsored by: Gandi.net Tested by: pho Feedback from: brooks, markj MFC after: 1 week Differential revision: https://reviews.freebsd.org/D18359
Notes
Notes: svn path=/head/; revision=341689
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+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.\" Copyright (c) 2018 Gandi
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd November 29, 2018
+.Dt FHLINK 2
+.Os
+.Sh NAME
+.Nm fhlink ,
+.Nm fhlinkat
+.Nd make a hard file link
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In unistd.h
+.Ft int
+.Fn fhlink "fhandle_t *fhp" "const char *to"
+.Ft int
+.Fn fhlinkat "fhandle_t *fhp" "int tofd" "const char *to"
+.Fc
+.Sh DESCRIPTION
+The
+.Fn fhlink
+system call
+atomically creates the specified directory entry (hard link)
+.Fa to
+with the attributes of the underlying object pointed at by
+.Fa fhp .
+If the link is successful: the link count of the underlying object
+is incremented;
+.Fa fhp
+and
+.Fa to
+share equal access and rights
+to the
+underlying object.
+.Pp
+If
+.Fa fhp
+is removed, the file
+.Fa to
+is not deleted and the link count of the
+underlying object is
+decremented.
+.Pp
+The object pointed at by the
+.Fa fhp
+argument
+must exist for the hard link to
+succeed and
+both
+.Fa fhp
+and
+.Fa to
+must be in the same file system.
+The
+.Fa fhp
+argument
+may not be a directory.
+.Pp
+The
+.Fn fhlinkat
+system call is equivalent to
+.Fa fhlink
+except in the case where
+.Fa to
+is a relative paths.
+In this case a relative path
+.Fa to
+is interpreted relative to
+the directory associated with the file descriptor
+.Fa tofd
+instead of the current working directory.
+.Pp
+Values for
+.Fa flag
+are constructed by a bitwise-inclusive OR of flags from the following
+list, defined in
+.In fcntl.h :
+.Bl -tag -width indent
+.It Dv AT_SYMLINK_FOLLOW
+If
+.Fa fhp
+names a symbolic link, a new link for the target of the symbolic link is
+created.
+.It Dv AT_BENEATH
+Only allow to link to a file which is beneath of the topping directory.
+See the description of the
+.Dv O_BENEATH
+flag in the
+.Xr open 2
+manual page.
+.El
+.Pp
+If
+.Fn fhlinkat
+is passed the special value
+.Dv AT_FDCWD
+in the
+.Fa tofd
+parameter, the current working directory is used for the
+.Fa to
+argument.
+If
+.Fa tofd
+has value
+.Dv AT_FDCWD ,
+the behavior is identical to a call to
+.Fn link .
+Unless
+.Fa flag
+contains the
+.Dv AT_SYMLINK_FOLLOW
+flag, if
+.Fa fhp
+names a symbolic link, a new link is created for the symbolic link
+.Fa fhp
+and not its target.
+.Sh RETURN VALUES
+.Rv -std link
+.Sh ERRORS
+The
+.Fn fhlink
+system call
+will fail and no link will be created if:
+.Bl -tag -width Er
+.It Bq Er ENOTDIR
+A component of
+.Fa to
+prefix is not a directory.
+.It Bq Er ENAMETOOLONG
+A component of
+.Fa to
+exceeded 255 characters,
+or entire length of
+.Fa to
+name exceeded 1023 characters.
+.It Bq Er ENOENT
+A component of
+.Fa to
+prefix does not exist.
+.It Bq Er EOPNOTSUPP
+The file system containing the file pointed at by
+.Fa fhp
+does not support links.
+.It Bq Er EMLINK
+The link count of the file pointed at by
+.Fa fhp
+would exceed 32767.
+.It Bq Er EACCES
+A component of
+.Fa to
+prefix denies search permission.
+.It Bq Er EACCES
+The requested link requires writing in a directory with a mode
+that denies write permission.
+.It Bq Er ELOOP
+Too many symbolic links were encountered in translating one of the pathnames.
+.It Bq Er ENOENT
+The file pointed at by
+.Fa fhp
+does not exist.
+.It Bq Er EEXIST
+The link named by
+.Fa to
+does exist.
+.It Bq Er EPERM
+The file pointed at by
+.Fa fhp
+is a directory.
+.It Bq Er EPERM
+The file pointed at by
+.Fa fhp
+has its immutable or append-only flag set, see the
+.Xr chflags 2
+manual page for more information.
+.It Bq Er EPERM
+The parent directory of the file named by
+.Fa to
+has its immutable flag set.
+.It Bq Er EXDEV
+The link named by
+.Fa to
+and the file pointed at by
+.Fa fhp
+are on different file systems.
+.It Bq Er ENOSPC
+The directory in which the entry for the new link is being placed
+cannot be extended because there is no space left on the file
+system containing the directory.
+.It Bq Er EDQUOT
+The directory in which the entry for the new link
+is being placed cannot be extended because the
+user's quota of disk blocks on the file system
+containing the directory has been exhausted.
+.It Bq Er EIO
+An I/O error occurred while reading from or writing to
+the file system to make the directory entry.
+.It Bq Er EROFS
+The requested link requires writing in a directory on a read-only file
+system.
+.It Bq Er EFAULT
+One of the pathnames specified
+is outside the process's allocated address space.
+.It Bq Er ESTALE
+The file handle
+.Fa fhp
+is no longer valid
+.El
+.Pp
+In addition to the errors returned by the
+.Fn fhlink ,
+the
+.Fn fhlinkat
+system call may fail if:
+.Bl -tag -width Er
+.It Bq Er EBADF
+The
+.Fa fhp
+or
+.Fa to
+argument does not specify an absolute path and the
+.Fa tofd
+argument, is not
+.Dv AT_FDCWD
+nor a valid file descriptor open for searching.
+.It Bq Er EINVAL
+The value of the
+.Fa flag
+argument is not valid.
+.It Bq Er ENOTDIR
+The
+.Fa fhp
+or
+.Fa to
+argument is not an absolute path and
+.Fa tofd
+is not
+.Dv AT_FDCWD
+nor a file descriptor associated with a directory.
+.El
+.Sh SEE ALSO
+.Xr fhstat 2 ,
+.Xr fhreadlink 2 ,
+.Xr fhopen 2 ,