NAME
disklabel,
readdisklabel,
writedisklabel,
setdisklabel,
bounds_check_with_label —
disk label management
routines
SYNOPSIS
#include
<sys/param.h>
#include <sys/disklabel.h>
int
readdisklabel(dev_t
dev, void (*strat)(struct
buf *), struct disklabel
*lp, int
spoofonly);
int
writedisklabel(dev_t
dev, void (*strat)(struct
buf *), struct disklabel
*lp);
int
setdisklabel(struct
disklabel *olp, struct
disklabel *nlp, u_int
openmask);
int
bounds_check_with_label(struct
buf *bp, struct disklabel
*lp);
DESCRIPTION
This collection of routines provides a disklabel management interface to kernel device drivers. These routines are classified as machine- or architecture-dependent because of restrictions imposed by the machine architecture and boot-strapping code on the location of the label, or because cooperation with other operating systems requires specialized conversion code.
readdisklabel()
attempts to read a disklabel from the device identified by
dev, using the device strategy routine passed in
strat. Note that a buffer structure is required to
pass to the strategy routine; it needs to be acquired and parametrized for
the intended I/O operation, and disposed of when the operation has
completed. Some fields in the disklabel passed in lp
may be pre-initialized by the caller in order to meet device driver
requirements for the I/O operation initiated to get to the disklabel data on
the medium. In particular, the field “d_secsize”, if non-zero,
is used by readdisklabel() to get an appropriately
sized buffer to pass to the device strategy routine. Unspecified fields in
lp should be set to zero. If the medium does not
contain a native disklabel that can be read in directly or
spoofonly argument is a true value, If a disk label is
found or can be constructed a value of 0 is returned. Otherwise the value of
the I/O errno encountered is returned.
writedisklabel()
stores disk label information contained in the disk label structure given by
lp on the device identified by
dev. Like readdisklabel(), it
acquires and sets up an I/O buffer to pass to the strategy routine
strat. writedisklabel()
returns 0 on success and EINVAL if the disk label
specifies invalid or unconvertible values. Otherwise, any error condition
reported by the device strategy routine in the buffer's
“b_error” field is returned.
setdisklabel()
checks a proposed new disk label passed in nlp for
some amount of basic sanity. This includes a check on attempts to change the
location, or reduce the size, of an existing disk partition that is
currently in use by the system. The current disposition of the disk
partitions is made available through olp and
openmask, which provide, respectively, the existing
disk label and a bit mask identifying the partitions that are currently in
use. Failure to pass on “basic sanity”, results in a
EINVAL return value, while a vetoed update of the
partition layout is signalled by a EBUSY return
value. Otherwise, 0 is returned.
bounds_check_with_label()
is used to check whether a device transfer described by
bp to the device identified by
dev, is properly contained within a disk partition of
the disk with label lp. If this check fails,
bounds_check_with_label() sets the buffer's
“b_error” field to
EINVAL and sets the B_ERROR
flag in “b_flags”. A value of -1 is
returned if any of the bound checks failed, a null transfer was attempted,
or transfer was attempted exactly at the end of the disk partition.
Otherwise the value of 0 is returned.