manuals: Fix some "missing section argument"

These were reported by `mandoc -T lint ...` as warnings.

Signed-off-by:	Graham Percival <gperciva@tarsnap.com>
Reviewed by:	mhorne, Alexander Ziaee <concussious.bugzilla@runbox.com>
Sponsored by:	Tarsnap Backup Inc.
Pull Request:	https://github.com/freebsd/freebsd-src/pull/1467

lib/libdevctl/devctl.3

@@ -209,7 +209,7 @@ method to construct the path.
 The
 .Fa buffer
 pointer is updated with an allocated buffer that must be freed with
-.Xr free .
+.Xr free 3 .
 .Pp
 The
 .Fn devctl_freeze

lib/libthr/libthr.3

@@ -217,7 +217,7 @@ recycle it at any moment, making this sysctl less useful than it sounds.
 .It Dv kern.ipc.umtx_max_robust
 The maximal number of robust mutexes allowed for one thread.
 The kernel will not unlock more mutexes than specified, see
-.Xr _umtx_op
+.Xr _umtx_op 2
 for more details.
 The default value is large enough for most useful applications.
 .It Dv debug.umtx.robust_faults_verbose

share/man/man4/disk.4

@@ -57,7 +57,7 @@ Operations to block devices such as
 .Xr lseek 2 ,
 .Xr read 2 ,
 and
-.Xr write
+.Xr write 2
 may only be performed at file offsets that are integral multiple of
 this size.
 .It Dv DIOCGMEDIASIZE

share/man/man4/ng_iface.4

@@ -153,8 +153,8 @@ to the desired level of nesting.
 .Xr netgraph 4 ,
 .Xr ng_cisco 4 ,
 .Xr ifconfig 8 ,
-.Xr ngctl 8
-.Xr sysctl
+.Xr ngctl 8 ,
+.Xr sysctl 8
 .Sh HISTORY
 The
 .Nm iface

share/man/man4/ng_nat.4

@@ -265,7 +265,7 @@ In case of
 .Nm
 failed to retrieve a certain counter
 from its
-.Xr libalias
+.Xr libalias 3
 instance, the corresponding field is returned as
 .Va UINT32_MAX .
 .It Dv NGM_NAT_SET_DLT Pq Ic setdlt

share/man/man4/qat.4

@@ -105,7 +105,7 @@ Following variables may be used to reconfigure the QAT device.\&
 For configuration persistence those variables may be set before loading the driver, either via
 .Xr kenv 1
 or
-.Xr loader.conf(5).
+.Xr loader.conf 5 .
 The device specific configuration options are prefixed with
 .Va dev.qat.X\&.
 where X is the device number.

share/man/man4/watchdog.4

@@ -42,7 +42,7 @@ supports several optional
 .Xr ioctl 2
 calls for configuration, and
 responds to a single operational
-.Xr ioctl
+.Xr ioctl 2
 call,
 .Dv WDIOCPATPAT .
 It takes a single argument which represents a timeout value specified as a
@@ -84,7 +84,7 @@ The watchdog might
 still be armed!
 .Pp
 The optional configuration
-.Xr ioctl
+.Xr ioctl 2
 commands are listed here, along with the type of the parameter used.
 Examples of their use can be found in
 .Xr watchdogd 8 .
@@ -127,7 +127,7 @@ printf(9)
 .Sh RETURN VALUES
 The
 .Dv WDIOCPATPAT
-.Xr ioctl
+.Xr ioctl 2
 returns zero on success and non-zero on failure.
 .Bl -tag -width Er
 .It Bq Er EOPNOTSUPP
@@ -141,7 +141,7 @@ Invalid flag combination passed.
 .El
 .Pp
 The configuration
-.Xr ioctl
+.Xr ioctl 2
 operations return zero on success and non-zero on failure.
 .Sh EXAMPLES
 .Bd -literal -offset indent

share/man/man9/VOP_ADVISE.9

@@ -39,7 +39,7 @@
 .Sh DESCRIPTION
 This call applies advice for a range of a file's data.
 It is used to implement the
-.Xr posix_fadvise
+.Xr posix_fadvise 2
 system call.
 .Pp
 Its arguments are:

share/man/man9/VOP_ALLOCATE.9

@@ -45,7 +45,7 @@
 .Sh DESCRIPTION
 This call allocates storage for a range of offsets in a file.
 It is used to implement the
-.Xr posix_fallocate
+.Xr posix_fallocate 2
 system call.
 .Pp
 Its arguments are:

share/man/man9/contigmalloc.9

@@ -105,7 +105,7 @@ The
 .Fn contigfree
 function is deprecated.
 Use
-.Xr free(9)
+.Xr free 9
 instead.
 .Sh IMPLEMENTATION NOTES
 The

share/man/man9/osd.9

@@ -396,7 +396,7 @@ API.
 .Pp
 .Fn osd_get
 only acquires an
-.Xr rmlock
+.Xr rmlock 9
 in read mode, therefore making it safe to use in the majority of contexts within
 the kernel including most fast paths.
 .Sh RETURN VALUES