Here is an improved version, after a lot of feedback from jmc@.
Quick list of changes:
* the unmount description moved closer to the top, since we
mention it in flags description anyway;
* list of mount options is now sorted;
* the description of the MNT_RELOAD flag was added;
* the descriptions of the MNT_FORCE and MNT_UPDATE flags were reworked
and moved to separate paragraphs.
Okay to commit?
--
WBR,
Vadim Zhukov
Index: mount.2
===================================================================
RCS file: /cvs/src/lib/libc/sys/mount.2,v
retrieving revision 1.46
diff -u -p -r1.46 mount.2
--- mount.2 27 May 2016 19:45:04 -0000 1.46
+++ mount.2 17 Jul 2016 22:13:06 -0000
@@ -70,31 +70,41 @@ at the time
of a successful mount are swept under the carpet, so to speak, and
are unavailable until the filesystem is unmounted.
.Pp
+The
+.Fn unmount
+function disassociates the filesystem from the specified
+mount point
+.Fa dir .
+.Pp
The following
.Fa flags
-may be specified to
-suppress default semantics which affect filesystem access.
+may be specified to change default behaviour:
.Bl -tag -width MNT_SYNCHRONOUS
-.It Dv MNT_RDONLY
-The filesystem should be treated as read-only:
-even the superuser may not write to it.
+.It Dv MNT_ASYNC
+All I/O to the filesystem should be done asynchronously.
.It Dv MNT_NOATIME
Do not update the access time on files in the filesystem unless
the modification or status change times are also being updated.
+.It Dv MNT_NODEV
+Do not interpret special files on the filesystem.
.It Dv MNT_NOEXEC
Do not allow files to be executed from the filesystem.
.It Dv MNT_NOSUID
Do not honor setuid or setgid bits on files when executing them.
-.It Dv MNT_NODEV
-Do not interpret special files on the filesystem.
-.It Dv MNT_SYNCHRONOUS
-All I/O to the filesystem should be done synchronously.
-.It Dv MNT_ASYNC
-All I/O to the filesystem should be done asynchronously.
+.It Dv MNT_RDONLY
+The filesystem should be treated as read-only:
+even the superuser may not write to it.
+.It Dv MNT_RELOAD
+Reload a MNT_RDONLY filesystem.
+Used, for example, by
+.Xr fsck 8
+after modification of on-disk structures.
.It Dv MNT_SOFTDEP
Use soft dependencies.
Applies to FFS filesystems only (see 'softdep' in
.Xr mount 8 ) .
+.It Dv MNT_SYNCHRONOUS
+All I/O to the filesystem should be done synchronously.
.It MNT_WXALLOWED
Processes that ask for memory to be made writeable plus executable
using the
@@ -108,10 +118,13 @@ The option is typically used on the
filesystem.
.El
.Pp
-The flag
+Two more flags affect the behaviour of system calls themselves,
+and not the behaviour of the corresponding filesystem:
+.Pp
+The
.Dv MNT_UPDATE
-indicates that the mount command is being applied
-to an already mounted filesystem.
+flag indicates that the mount command is being applied to an already
+mounted filesystem.
This allows the mount flags to be changed without requiring
that the filesystem be unmounted and remounted.
Some filesystems may not allow all flags to be changed.
@@ -119,6 +132,18 @@ For example,
most filesystems will not allow a change from read-write to read-only.
.Pp
The
+.Dv MNT_FORCE
+flag, if used together with
+.Dv MNT_UPDATE ,
+allows transition from read-write to read-only,
+even if there are files open for writing.
+And when used on unmount, it specifies that the filesystem
+should be forcibly unmounted even if files are still active;
+active special devices continue to work,
+but any further access to any other active files result in errors,
+even if the filesystem is later remounted.
+.Pp
+The
.Fa type
argument defines the type of the filesystem.
The types of filesystems known to the system are defined in
@@ -237,22 +262,6 @@ struct udf_args {
char *fspec; /* block special device to mount */
};
.Ed
-.Pp
-The
-.Fn unmount
-function call disassociates the filesystem from the specified
-mount point
-.Fa dir .
-.Pp
-The
-.Fa flags
-argument may specify
-.Dv MNT_FORCE
-to specify that the filesystem should be forcibly unmounted even if files are
-still active.
-Active special devices continue to work,
-but any further accesses to any other active files result in errors
-even if the filesystem is later remounted.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
