libmount: revert X-* and x-* meaning

Let's hope this is last change necessary to cleanup x-* usage:

  x-*  persistent option, stored in utab, available for umount, etc.
  X-*  fstab comment only

mount(8) supports x-mount.mkdir= as well as newly recommended X-mount.mkdir=

Advantages:

 * less invasive
 * does not require exception for x-systemd
 * does not require rename x-initrd to X-initrd

The systemd and dracut users will get the new (=fixed) functionality without a
change in fstab configuration. This is the primary goal.

Disadvantages:

 * not 100% compatible libmount behavior, x-* options have not been
   previously stored in utab. The API is the same, options will be still
   available, but on x-* libmount will write to /run/mount/utab. For now
   it seems only systemd uses x-*, and they like this behavior, so...

Addresses: https://github.com/systemd/systemd/pull/4515
Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 16 insertions, 14 deletions

diff --git a/sys-utils/mount.8 b/sys-utils/mount.8
index f80b20252..54ad0d8d0 100644
--- a/sys-utils/mount.8
+++ b/sys-utils/mount.8
@@ -1142,32 +1142,34 @@ This option implies the options
 (unless overridden by subsequent options, as in the option line
 .BR users,exec,dev,suid ).
 .TP
-.B x-*
-All options prefixed with "x-" are interpreted as comments or as userspace
+.B X-*
+All options prefixed with "X-" are interpreted as comments or as userspace
 application-specific options.  These options are not stored in the user space (e.g. mtab file),
 nor sent to the mount.\fItype\fR helpers nor to the
 .BR mount (2)
-system call.  The suggested format is \fBx-\fIappname\fR.\fIoption\fR.
+system call.  The suggested format is \fBX-\fIappname\fR.\fIoption\fR.
 .TP
-.B X-*
-The same as \fBx-*\fR options, but stored permanently in the user space. It
+.B x-*
+The same as \fBX-*\fR options, but stored permanently in the user space. It
 means the options are also available for umount or another operations.  Note
-that maintain mount options in user space is a bad idea, because it's necessary
-to link all tools that use the options with libmount and there is no guarantee that the
-options will be always available (for example after a move mount operation or in
-unshared namespace).
-
-Note that x-systemd mount options are maintained as X-* options, the rename is
-unnecessary to keep existing fstab settings backwardly compatible.
+that maintain mount options in user space is tricky, because it's necessary use
+libmount based tools and there is no guarantee that the options will be always
+available (for example after a move mount operation or in unshared namespace).
 
+Note that before util-linux v2.30 the x-* options have not been maintained by
+libmount and stored in user space (functionality was the same as have X-* now),
+but due to growing number of use-cases (in initrd, systemd etc.) the
+functionality have been extended to keep existing fstab configurations usable
+without a change.
 .TP
-.BR x-mount.mkdir [ = \fImode\fR ]
+.BR X-mount.mkdir [ = \fImode\fR ]
 Allow to make a target directory (mountpoint).  The optional argument
 .I mode
 specifies the filesystem access mode used for
 .BR mkdir (2)
 in octal notation.  The default mode is 0755.  This functionality is supported
-only for root users.
+only for root users.  The option is also supported as x-mount.mkdir, this notation
+is deprecated for mount.mkdir since v2.30.
 
 .SH "FILESYSTEM-SPECIFIC MOUNT OPTIONS"
 The following options apply only to certain filesystems.