Re: [PATCH 2/2 V2] man2: New page documenting filesystem get/set label ioctls

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

Hello Eric,

So it seems like this feature eventually got merged in Linux 4.18. Is
this page up to date with what went into the kernel?

Thanks,

Michael

On Thu, 10 May 2018 at 19:29, Eric Sandeen <sandeen@sandeen.net> wrote:
>
> This documents the proposed new vfs-level ioctls which can
> get or set a mounted filesytem's label.
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>
> V2: make primary file ioctl_getfslabel, link ioctl_setfslabel to it
>     note that getfslabel requires CAP_SYS_ADMIN
>
> diff --git a/man2/ioctl_getfslabel.2 b/man2/ioctl_getfslabel.2
> new file mode 100644
> index 0000000..2c3375c
> --- /dev/null
> +++ b/man2/ioctl_getfslabel.2
> @@ -0,0 +1,87 @@
> +.\" Copyright (c) 2018, Red Hat, Inc.  All rights reserved.
> +.\"
> +.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
> +.\" This is free documentation; you can redistribute it and/or
> +.\" modify it under the terms of the GNU General Public License as
> +.\" published by the Free Software Foundation; either version 2 of
> +.\" the License, or (at your option) any later version.
> +.\"
> +.\" The GNU General Public License's references to "object code"
> +.\" and "executables" are to be interpreted as the output of any
> +.\" document formatting or typesetting system, including
> +.\" intermediate and printed output.
> +.\"
> +.\" This manual is distributed in the hope that it will be useful,
> +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
> +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +.\" GNU General Public License for more details.
> +.\"
> +.\" You should have received a copy of the GNU General Public
> +.\" License along with this manual; if not, see
> +.\" <http://www.gnu.org/licenses/>.
> +.\" %%%LICENSE_END
> +.TH IOCTL-FSLABEL 2 2018-05-02 "Linux" "Linux Programmer's Manual"
> +.SH NAME
> +ioctl_fslabel \- get or set a filesystem label
> +.SH SYNOPSIS
> +.br
> +.B #include <sys/ioctl.h>
> +.br
> +.B #include <linux/fs.h>
> +.sp
> +.BI "int ioctl(int " fd ", FS_IOC_GETFSLABEL, char " label [FSLABEL_MAX]);
> +.br
> +.BI "int ioctl(int " fd ", FS_IOC_SETFSLABEL, char " label [FSLABEL_MAX]);
> +.SH DESCRIPTION
> +If a filesystem supports online label manipulation, these
> +.BR ioctl (2)
> +operations can be used to get or set the filesystem label for the filesystem
> +on which
> +.B fd
> +resides.
> +The
> +.B FS_IOC_SETFSLABEL
> +operation requires privilege
> +.RB ( CAP_SYS_ADMIN ).
> +.SH RETURN VALUE
> +On success zero is returned.  On error, \-1 is returned, and
> +.I errno
> +is set to indicate the error.
> +.PP
> +.SH ERRORS
> +Error codes can be one of, but are not limited to, the following:
> +.TP
> +.B EINVAL
> +The specified label exceeds the maximum label length for the filesystem.
> +.TP
> +.B ENOTTY
> +This can appear if the filesystem does not support online label manipulation.
> +.TP
> +.B EPERM
> +The calling process does not have sufficient permissions to set the label.
> +.TP
> +.B EFAULT
> +.I label
> +references an inaccessible memory area.
> +.SH VERSIONS
> +These ioctl operations first appeared in Linux 4.18.
> +They were previously known as
> +.B BTRFS_IOC_GET_FSLABEL
> +and
> +.B BTRFS_IOC_SET_FSLABEL
> +and were private to Btrfs.
> +.SH CONFORMING TO
> +This API is Linux-specific.
> +.SH NOTES
> +The maximum string length for this interface is
> +.BR FSLABEL_MAX ,
> +including the terminating null byte (\(aq\\0\(aq).
> +Filesystems have differing maximum label lengths, which may or
> +may not include the terminating null.  The string provided to
> +.B FS_IOC_SETFSLABEL
> +must always be null-terminated, and the string returned by
> +.B FS_IOC_GETFSLABEL
> +will always be null-terminated.
> +.SH SEE ALSO
> +.BR ioctl (2),
> +.BR blkid (8)
> diff --git a/man2/ioctl_setfslabel.2 b/man2/ioctl_setfslabel.2
> new file mode 100644
> index 0000000..2119835
> --- /dev/null
> +++ b/man2/ioctl_setfslabel.2
> @@ -0,0 +1 @@
> +.so man2/ioctl_getfslabel.2
>


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/