Disklabel separation work - Generally shift all disklabel-specific

[dragonfly/vkernel-mp.git] / sys / kern / subr_diskslice.c

/*-
 * Copyright (c) 1994 Bruce D. Evans.
 * All rights reserved.
 *
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * Copyright (c) 1982, 1986, 1988 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)wd.c  7.2 (Berkeley) 5/9/91
 *      from: wd.c,v 1.55 1994/10/22 01:57:12 phk Exp $
 *      from: @(#)ufs_disksubr.c        7.16 (Berkeley) 5/4/91
 *      from: ufs_disksubr.c,v 1.8 1994/06/07 01:21:39 phk Exp $
 * $FreeBSD: src/sys/kern/subr_diskslice.c,v 1.82.2.6 2001/07/24 09:49:41 dd Exp $
 * $DragonFly: src/sys/kern/subr_diskslice.c,v 1.45 2007/06/17 23:50:16 dillon Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/disklabel.h>
#include <sys/diskslice.h>
#include <sys/disk.h>
#include <sys/diskmbr.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>
#include <sys/stat.h>
#include <sys/syslog.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/device.h>
#include <sys/thread2.h>

#include <vfs/ufs/dinode.h>     /* XXX used only for fs.h */
#include <vfs/ufs/fs.h>         /* XXX used only to get BBSIZE/SBSIZE */

static void dsiodone (struct bio *bio);
static int  dsreadandsetlabel(cdev_t dev, u_int flags,
                           struct diskslices *ssp, struct diskslice *sp,
                           struct disk_info *info);
static void free_ds_label (struct diskslices *ssp, int slice);
static void set_ds_label (struct diskslices *ssp, int slice,
                              struct disklabel *lp);
static void set_ds_wlabel (struct diskslices *ssp, int slice, int wlabel);

/*
 * Determine the size of the transfer, and make sure it is
 * within the boundaries of the partition. Adjust transfer
 * if needed, and signal errors or early completion.
 *
 * XXX TODO:
 *      o Split buffers that are too big for the device.
 *      o Check for overflow.
 *      o Finish cleaning this up.
 *
 * This function returns 1 on success, 0 if transfer equates
 * to EOF (end of disk) or -1 on failure.  The appropriate 
 * 'errno' value is also set in bp->b_error and bp->b_flags
 * is marked with B_ERROR.
 */
struct bio *
dscheck(cdev_t dev, struct bio *bio, struct diskslices *ssp)
{
        struct buf *bp = bio->bio_buf;
        struct bio *nbio;
        struct disklabel *lp;
        char *msg;
        long nsec;
        u_int64_t secno;
        u_int64_t endsecno;
        u_int64_t slicerel_secno;
        struct diskslice *sp;
        u_int32_t part;
        u_int32_t slice;
        int shift;
        int mask;
        int snoop;

        slice = dkslice(dev);
        part  = dkpart(dev);

        if (bio->bio_offset < 0) {
                kprintf("dscheck(%s): negative bio_offset %lld\n", 
                        devtoname(dev), bio->bio_offset);
                goto bad;
        }
        if (slice >= ssp->dss_nslices) {
                kprintf("dscheck(%s): slice too large %d/%d\n",
                        devtoname(dev), slice, ssp->dss_nslices);
                goto bad;
        }
        sp = &ssp->dss_slices[slice];

        /*
         * Calculate secno and nsec
         */
        if (ssp->dss_secmult == 1) {
                shift = DEV_BSHIFT;
                goto doshift;
        } else if (ssp->dss_secshift != -1) {
                shift = DEV_BSHIFT + ssp->dss_secshift;
doshift:
                mask = (1 << shift) - 1;
                if ((int)bp->b_bcount & mask)
                        goto bad_bcount;
                if ((int)bio->bio_offset & mask)
                        goto bad_blkno;
                secno = bio->bio_offset >> shift;
                nsec = bp->b_bcount >> shift;
        } else {
                if (bp->b_bcount % ssp->dss_secsize)
                        goto bad_bcount;
                if (bio->bio_offset % ssp->dss_secsize)
                        goto bad_blkno;
                secno = bio->bio_offset / ssp->dss_secsize;
                nsec = bp->b_bcount / ssp->dss_secsize;
        }

        /*
         * Calculate slice-relative sector number end slice-relative
         * limit.
         */
        if (slice == WHOLE_DISK_SLICE) {
                /*
                 * Labels have not been allowed on whole-disks for a while.
                 * This really puts the nail in the coffin... no disk
                 * snooping will occur even if you tried to write a label
                 * without a slice structure.
                 *
                 * Accesses to the WHOLE_DISK_SLICE do not use a disklabel
                 * and partition numbers are special-cased.  Currently numbers
                 * less then 128 are not allowed.  Partition numbers >= 128
                 * are encoded in the high 8 bits of the 64 bit buffer offset
                 * and are fed directly through to the device with no
                 * further interpretation.  In particular, no sector
                 * translation interpretation should occur because the
                 * sector size for the special raw access may not be the
                 * same as the nominal sector size for the device.
                 */
                lp = NULL;
                if (part < 128) {
                        kprintf("dscheck(%s): illegal partition number (%d) "
                                "for WHOLE_DISK_SLICE access\n",
                                devtoname(dev), part);
                        goto bad;
                } else if (part != WHOLE_SLICE_PART) {
                        nbio = push_bio(bio);
                        nbio->bio_offset = bio->bio_offset |
                                           (u_int64_t)part << 56;
                        return(nbio);
                }

                /*
                 * sp->ds_size is for the whole disk in the WHOLE_DISK_SLICE,
                 * there are no reserved areas.
                 */
                endsecno = sp->ds_size;
                slicerel_secno = secno;
                snoop = 0;
        } else if (part == WHOLE_SLICE_PART) {
                /* 
                 * We are accessing a slice.  Enable snooping of the bsd
                 * label.  Note that snooping only occurs if ds_reserved
                 * is also non-zero.  ds_reserved will be non-zero if
                 * an in-core label is present or snooping has been
                 * explicitly requested via an ioctl().
                 *
                 * NOTE! opens on a whole-slice partition will not attempt
                 * to read a disklabel in, so there may not be an in-core
                 * disklabel even if there is one on the disk.
                 */
                endsecno = sp->ds_size;
                slicerel_secno = secno;
                snoop = 1;
        } else if ((lp = sp->ds_label) != NULL) {
                /*
                 * A label is present, extract the partition.  Snooping of
                 * the disklabel is not supported even if accessible.  Of
                 * course, the reserved area is still write protected.
                 */
                if (getpartbounds(lp, part, &slicerel_secno, &endsecno)) {
                        kprintf("dscheck(%s): partition %d out of bounds\n",
                                devtoname(dev), part);
                        goto bad;
                }
                slicerel_secno += secno;
                snoop = 0;
        } else {
                /*
                 * Attempt to access partition when no disklabel present
                 */
                kprintf("dscheck(%s): attempt to access non-existant partition\n",
                        devtoname(dev));
                goto bad;
        }

        /*
         * Disallow writes to reserved areas unless ds_wlabel allows it.
         */
        if (slicerel_secno < sp->ds_reserved && nsec &&
            bp->b_cmd != BUF_CMD_READ && sp->ds_wlabel == 0) {
                bp->b_error = EROFS;
                goto error;
        }

        /*
         * If we get here, bio_offset must be on a block boundary and
         * the sector size must be a power of 2.
         */
        if ((bio->bio_offset & (ssp->dss_secsize - 1)) ||
            (ssp->dss_secsize ^ (ssp->dss_secsize - 1)) !=
            ((ssp->dss_secsize << 1) - 1)) {
                kprintf("%s: invalid BIO offset, not sector aligned or"
                        " invalid sector size (not power of 2) %08llx %d\n",
                        devtoname(dev), bio->bio_offset, ssp->dss_secsize);
                goto bad;
        }

        /*
         * EOF handling
         */
        if (secno + nsec > endsecno) {
                /*
                 * Return an error if beyond the end of the disk, or
                 * if B_BNOCLIP is set.  Tell the system that we do not
                 * need to keep the buffer around.
                 */
                if (secno > endsecno || (bp->b_flags & B_BNOCLIP))
                        goto bad;

                /*
                 * If exactly at end of disk, return an EOF.  Throw away
                 * the buffer contents, if any, by setting B_INVAL.
                 */
                if (secno == endsecno) {
                        bp->b_resid = bp->b_bcount;
                        bp->b_flags |= B_INVAL;
                        goto done;
                }

                /*
                 * Else truncate
                 */
                nsec = endsecno - secno;
                bp->b_bcount = nsec * ssp->dss_secsize;
        }

        nbio = push_bio(bio);
        nbio->bio_offset = (off_t)(sp->ds_offset + slicerel_secno) * 
                           ssp->dss_secsize;

        /*
         * Snoop reads and writes to the label area - only done if
         * snoop is non-zero, ds_reserved is non-zero, and the
         * read covers the label sector.
         */
        if (snoop && slicerel_secno < sp->ds_reserved &&
            slicerel_secno <= LABELSECTOR &&
            nsec && slicerel_secno + nsec > LABELSECTOR) {
                /* 
                 * Set up our own callback on I/O completion to handle
                 * undoing the fixup we did for the write as well as
                 * doing the fixup for a read.
                 *
                 * Set info2.offset to the offset within the buffer containing
                 * the start of the label.
                 */
                nbio->bio_done = dsiodone;
                nbio->bio_caller_info1.ptr = sp;
                nbio->bio_caller_info2.offset =
                        (LABELSECTOR - slicerel_secno) * ssp->dss_secsize;
                if (bp->b_cmd != BUF_CMD_READ) {
                        msg = fixlabel(
                                NULL, sp,
                               (struct disklabel *)
                               (bp->b_data + (int)nbio->bio_caller_info2.offset),
                               TRUE);
                        if (msg != NULL) {
                                kprintf("dscheck(%s): %s\n", 
                                    devtoname(dev), msg);
                                bp->b_error = EROFS;
                                pop_bio(nbio);
                                goto error;
                        }
                }
        }
        return (nbio);

bad_bcount:
        kprintf(
        "dscheck(%s): b_bcount %d is not on a sector boundary (ssize %d)\n",
            devtoname(dev), bp->b_bcount, ssp->dss_secsize);
        goto bad;

bad_blkno:
        kprintf(
        "dscheck(%s): bio_offset %lld is not on a sector boundary (ssize %d)\n",
            devtoname(dev), bio->bio_offset, ssp->dss_secsize);
bad:
        bp->b_error = EINVAL;
        /* fall through */
error:
        /*
         * Terminate the I/O with a ranging error.  Since the buffer is
         * either illegal or beyond the file EOF, mark it B_INVAL as well.
         */
        bp->b_resid = bp->b_bcount;
        bp->b_flags |= B_ERROR | B_INVAL;
done:
        /*
         * Caller must biodone() the originally passed bio if NULL is
         * returned.
         */
        return (NULL);
}

void
dsclose(cdev_t dev, int mode, struct diskslices *ssp)
{
        u_int32_t part;
        u_int32_t slice;
        struct diskslice *sp;

        slice = dkslice(dev);
        part  = dkpart(dev);
        if (slice < ssp->dss_nslices) {
                sp = &ssp->dss_slices[slice];
                dsclrmask(sp, part);
        }
}

void
dsgone(struct diskslices **sspp)
{
        int slice;
        struct diskslice *sp;
        struct diskslices *ssp;

        for (slice = 0, ssp = *sspp; slice < ssp->dss_nslices; slice++) {
                sp = &ssp->dss_slices[slice];
                free_ds_label(ssp, slice);
        }
        kfree(ssp, M_DEVBUF);
        *sspp = NULL;
}

/*
 * For the "write" commands (DIOCSDINFO and DIOCWDINFO), this
 * is subject to the same restriction as dsopen().
 */
int
dsioctl(cdev_t dev, u_long cmd, caddr_t data, int flags,
        struct diskslices **sspp, struct disk_info *info)
{
        int error;
        struct disklabel *lp;
        int old_wlabel;
        u_int32_t openmask[DKMAXPARTITIONS/(sizeof(u_int32_t)*8)];
        u_int64_t old_reserved;
        int part;
        int slice;
        struct diskslice *sp;
        struct diskslices *ssp;

        slice = dkslice(dev);
        part = dkpart(dev);
        ssp = *sspp;
        if (slice >= ssp->dss_nslices)
                return (EINVAL);
        sp = &ssp->dss_slices[slice];
        lp = sp->ds_label;

        switch (cmd) {
        case DIOCGDVIRGIN:
                /*
                 * You can only retrieve a virgin disklabel on the whole
                 * disk slice or whole-slice partition.
                 */
                if (slice != WHOLE_DISK_SLICE &&
                    part != WHOLE_SLICE_PART) {
                        return(EINVAL);
                }

                lp = (struct disklabel *)data;
                makevirginlabel(lp, ssp, sp, info);
                return (0);

        case DIOCGDINFO:
                /*
                 * You can only retrieve a disklabel on the whole
                 * slice partition.
                 *
                 * We do not support labels directly on whole-disks
                 * any more (that is, disks without slices), unless the
                 * device driver has asked for a compatible label (e.g.
                 * for a CD) to allow booting off of storage that is
                 * otherwise unlabeled.
                 */
                error = 0;
                if (part != WHOLE_SLICE_PART)
                        return(EINVAL);
                if (slice == WHOLE_DISK_SLICE &&
                    (info->d_dsflags & DSO_COMPATLABEL) == 0) {
                        return (ENODEV);
                }
                if (sp->ds_label == NULL) {
                        error = dsreadandsetlabel(dev, info->d_dsflags,
                                                  ssp, sp, info);
                }
                if (error == 0)
                        *(struct disklabel *)data = *sp->ds_label;
                return (error);

        case DIOCGPART:
                {
                        struct partinfo *dpart = (void *)data;

                        /*
                         * The disk management layer may not have read the
                         * disklabel yet because simply opening a slice no
                         * longer 'probes' the disk that way.  Be sure we
                         * have tried.
                         *
                         * We ignore any error.
                         */
                        if (sp->ds_label == NULL && part == WHOLE_SLICE_PART &&
                            slice != WHOLE_DISK_SLICE) {
                                dsreadandsetlabel(dev, info->d_dsflags,
                                                  ssp, sp, info);
                        }

                        bzero(dpart, sizeof(*dpart));
                        dpart->media_offset   = (u_int64_t)sp->ds_offset *
                                                info->d_media_blksize;
                        dpart->media_size     = (u_int64_t)sp->ds_size *
                                                info->d_media_blksize;
                        dpart->media_blocks   = sp->ds_size;
                        dpart->media_blksize  = info->d_media_blksize;
                        dpart->reserved_blocks= sp->ds_reserved;

                        if (slice != WHOLE_DISK_SLICE &&
                            part != WHOLE_SLICE_PART) {
                                u_int64_t start;
                                u_int64_t blocks;
                                if (lp == NULL)
                                        return(EINVAL);
                                if (getpartbounds(lp, part, &start, &blocks))
                                        return(EINVAL);
                                dpart->fstype = getpartfstype(lp, part);
                                dpart->media_offset += start *
                                                       info->d_media_blksize;
                                dpart->media_size = blocks *
                                                    info->d_media_blksize;
                                dpart->media_blocks = blocks;

                                /*
                                 * partition starting sector (p_offset)
                                 * requires slice's reserved areas to be
                                 * adjusted.
                                 */
                                if (dpart->reserved_blocks > start)
                                        dpart->reserved_blocks -= start;
                                else
                                        dpart->reserved_blocks = 0;
                        }

                        /*
                         * Load remaining fields from the info structure
                         */
                        dpart->d_nheads =       info->d_nheads;
                        dpart->d_ncylinders =   info->d_ncylinders;
                        dpart->d_secpertrack =  info->d_secpertrack;
                        dpart->d_secpercyl =    info->d_secpercyl;
                }
                return (0);

        case DIOCGSLICEINFO:
                bcopy(ssp, data, (char *)&ssp->dss_slices[ssp->dss_nslices] -
                                 (char *)ssp);
                return (0);

        case DIOCSDINFO:
                /*
                 * You can write a disklabel on the whole disk slice or
                 * whole-slice partition.
                 */
                if (slice != WHOLE_DISK_SLICE &&
                    part != WHOLE_SLICE_PART) {
                        return(EINVAL);
                }

                /*
                 * We no longer support writing disklabels directly to media
                 * without there being a slice.  Keep this as a separate
                 * conditional.
                 */
                if (slice == WHOLE_DISK_SLICE)
                        return (ENODEV);

                if (!(flags & FWRITE))
                        return (EBADF);
                lp = kmalloc(sizeof *lp, M_DEVBUF, M_WAITOK);
                if (sp->ds_label == NULL)
                        bzero(lp, sizeof *lp);
                else
                        bcopy(sp->ds_label, lp, sizeof *lp);
                if (sp->ds_label == NULL) {
                        bzero(openmask, sizeof(openmask));
                } else {
                        bcopy(sp->ds_openmask, openmask, sizeof(openmask));
                }
                error = setdisklabel(lp, (struct disklabel *)data,
                                     sp, openmask);
                if (error != 0) {
                        kfree(lp, M_DEVBUF);
                        return (error);
                }
                free_ds_label(ssp, slice);
                set_ds_label(ssp, slice, lp);
                return (0);

        case DIOCSYNCSLICEINFO:
                /*
                 * This ioctl can only be done on the whole disk
                 */
                if (slice != WHOLE_DISK_SLICE || part != WHOLE_SLICE_PART)
                        return (EINVAL);

                if (*(int *)data == 0) {
                        for (slice = 0; slice < ssp->dss_nslices; slice++) {
                                struct diskslice *ds = &ssp->dss_slices[slice];

                                switch(dscountmask(ds)) {
                                case 0:
                                        break;
                                case 1:
                                        if (slice != WHOLE_DISK_SLICE)
                                                return (EBUSY);
                                        if (!dschkmask(ds, RAW_PART))
                                                return (EBUSY);
                                        break;
                                default:
                                        return (EBUSY);
                                }
                        }
                }

                /*
                 * Temporarily forget the current slices struct and read
                 * the current one.
                 *
                 * NOTE:
                 *
                 * XXX should wait for current accesses on this disk to
                 * complete, then lock out future accesses and opens.
                 */
                *sspp = NULL;
                lp = kmalloc(sizeof *lp, M_DEVBUF, M_WAITOK);
                *lp = *ssp->dss_slices[WHOLE_DISK_SLICE].ds_label;
                error = dsopen(dev, S_IFCHR, ssp->dss_oflags, sspp, info);
                if (error != 0) {
                        kfree(lp, M_DEVBUF);
                        *sspp = ssp;
                        return (error);
                }

                /*
                 * Reopen everything.  This is a no-op except in the "force"
                 * case and when the raw bdev and cdev are both open.  Abort
                 * if anything fails.
                 */
                for (slice = 0; slice < ssp->dss_nslices; slice++) {
                        for (part = 0; part < DKMAXPARTITIONS; ++part) {
                                if (!dschkmask(&ssp->dss_slices[slice], part))
                                        continue;
                                error = dsopen(dkmodslice(dkmodpart(dev, part),
                                                          slice),
                                               S_IFCHR, ssp->dss_oflags, sspp,
                                               info);
                                if (error != 0) {
                                        kfree(lp, M_DEVBUF);
                                        *sspp = ssp;
                                        return (EBUSY);
                                }
                        }
                }

                kfree(lp, M_DEVBUF);
                dsgone(&ssp);
                return (0);

        case DIOCWDINFO:
                error = dsioctl(dev, DIOCSDINFO, data, flags, &ssp, info);
                if (error != 0)
                        return (error);

                /*
                 * Set the reserved area
                 */
                old_wlabel = sp->ds_wlabel;
                set_ds_wlabel(ssp, slice, TRUE);
                old_reserved = sp->ds_reserved;
                sp->ds_reserved = SBSIZE / ssp->dss_secsize;
                error = writedisklabel(dev, sp->ds_label);
                set_ds_wlabel(ssp, slice, old_wlabel);
                sp->ds_reserved = old_reserved;
                /* XXX should invalidate in-core label if write failed. */
                return (error);

        case DIOCSETSNOOP:
                /*
                 * Set label snooping even if there is no label present.
                 */
                if (slice == WHOLE_DISK_SLICE || part != WHOLE_SLICE_PART)
                        return (EINVAL);
                if (lp == NULL) {
                        if (*(int *)data) {
                                sp->ds_reserved = SBSIZE / ssp->dss_secsize;
                        } else {
                                sp->ds_reserved = 0;
                        }
                }
                return (0);

        case DIOCWLABEL:
                if (slice == WHOLE_DISK_SLICE)
                        return (ENODEV);
                if (!(flags & FWRITE))
                        return (EBADF);
                set_ds_wlabel(ssp, slice, *(int *)data != 0);
                return (0);

        default:
                return (ENOIOCTL);
        }
}

/*
 * Chain the bio_done.  b_cmd remains valid through such chaining.
 */
static void
dsiodone(struct bio *bio)
{
        struct buf *bp = bio->bio_buf;
        char *msg;

        if (bp->b_cmd != BUF_CMD_READ
            || (!(bp->b_flags & B_ERROR) && bp->b_error == 0)) {
                msg = fixlabel(NULL, bio->bio_caller_info1.ptr,
                               (struct disklabel *)
                               (bp->b_data + (int)bio->bio_caller_info2.offset),
                               FALSE);
                if (msg != NULL)
                        kprintf("%s\n", msg);
        }
        biodone(bio->bio_prev);
}

int
dsisopen(struct diskslices *ssp)
{
        int slice;

        if (ssp == NULL)
                return (0);
        for (slice = 0; slice < ssp->dss_nslices; slice++) {
                if (dscountmask(&ssp->dss_slices[slice]))
                        return (1);
        }
        return (0);
}

/*
 * Allocate a slices "struct" and initialize it to contain only an empty
 * compatibility slice (pointing to itself), a whole disk slice (covering
 * the disk as described by the label), and (nslices - BASE_SLICES) empty
 * slices beginning at BASE_SLICE.
 *
 * Note that the compatibility slice is no longer really a compatibility
 * slice.  It is slice 0 if a GPT label is present, and the dangerously
 * dedicated slice if no slice table otherwise exists.  Else it is 0-sized.
 */
struct diskslices *
dsmakeslicestruct(int nslices, struct disk_info *info)
{
        struct diskslice *sp;
        struct diskslices *ssp;

        ssp = kmalloc(offsetof(struct diskslices, dss_slices) +
                     nslices * sizeof *sp, M_DEVBUF, M_WAITOK);
        ssp->dss_first_bsd_slice = COMPATIBILITY_SLICE;
        ssp->dss_nslices = nslices;
        ssp->dss_oflags = 0;

        /*
         * Figure out if we can use shifts or whether we have to
         * use mod/multply to translate byte offsets into sector numbers.
         */
        if ((info->d_media_blksize ^ (info->d_media_blksize - 1)) ==
             (info->d_media_blksize << 1) - 1) {
                ssp->dss_secmult = info->d_media_blksize / DEV_BSIZE;
                if (ssp->dss_secmult & (ssp->dss_secmult - 1))
                        ssp->dss_secshift = -1;
                else
                        ssp->dss_secshift = ffs(ssp->dss_secmult) - 1;
        } else {
                ssp->dss_secmult = 0;
                ssp->dss_secshift = -1;
        }
        ssp->dss_secsize = info->d_media_blksize;
        sp = &ssp->dss_slices[0];
        bzero(sp, nslices * sizeof *sp);
        sp[WHOLE_DISK_SLICE].ds_size = info->d_media_blocks;
        return (ssp);
}

char *
dsname(cdev_t dev, int unit, int slice, int part, char *partname)
{
        static char name[32];
        const char *dname;
        int used;

        dname = dev_dname(dev);
        if (strlen(dname) > 16)
                dname = "nametoolong";
        ksnprintf(name, sizeof(name), "%s%d", dname, unit);
        partname[0] = '\0';
        used = strlen(name);

        if (slice != WHOLE_DISK_SLICE) {
                /*
                 * slice or slice + partition.  BASE_SLICE is s1, but
                 * the compatibility slice (0) needs to be s0.
                 */
                used += ksnprintf(name + used, sizeof(name) - used,
                                  "s%d", (slice ? slice - BASE_SLICE + 1 : 0));
                if (part != WHOLE_SLICE_PART) {
                        used += ksnprintf(name + used, sizeof(name) - used,
                                          "%c", 'a' + part);
                        partname[0] = 'a' + part;
                        partname[1] = 0;
                }
        } else if (part == WHOLE_SLICE_PART) {
                /*
                 * whole-disk-device, raw access to disk
                 */
                /* no string extension */
        } else if (part > 128) {
                /*
                 * whole-disk-device, extended raw access partitions.
                 * (typically used to access CD audio tracks)
                 */
                used += ksnprintf(name + used, sizeof(name) - used,
                                          "t%d", part - 128);
        } else {
                /*
                 * whole-disk-device, illegal partition number
                 */
                used += ksnprintf(name + used, sizeof(name) - used,
                                          "?%d", part);
        }
        return (name);
}

/*
 * This should only be called when the unit is inactive and the strategy
 * routine should not allow it to become active unless we call it.  Our
 * strategy routine must be special to allow activity.
 */
int
dsopen(cdev_t dev, int mode, u_int flags, 
        struct diskslices **sspp, struct disk_info *info)
{
        cdev_t dev1;
        int error;
        int need_init;
        struct diskslice *sp;
        struct diskslices *ssp;
        int slice;
        int part;

        dev->si_bsize_phys = info->d_media_blksize;

        /*
         * Do not attempt to read the slice table or disk label when
         * accessing the whole-disk slice or a while-slice partition.
         */
        if (dkslice(dev) == WHOLE_DISK_SLICE)
                flags |= DSO_ONESLICE | DSO_NOLABELS;
        if (dkpart(dev) == WHOLE_SLICE_PART)
                flags |= DSO_NOLABELS;

        /*
         * Reinitialize the slice table unless there is an open device
         * on the unit.
         *
         * It would be nice if we didn't have to do this but when a
         * user is slicing and partitioning up a disk it is a lot safer
         * to not take any chances.
         */
        ssp = *sspp;
        need_init = !dsisopen(ssp);
        if (ssp != NULL && need_init)
                dsgone(sspp);
        if (need_init) {
                /*
                 * Allocate a minimal slices "struct".  This will become
                 * the final slices "struct" if we don't want real slices
                 * or if we can't find any real slices.
                 *
                 * Then scan the disk
                 */
                *sspp = dsmakeslicestruct(BASE_SLICE, info);

                if ((flags & DSO_ONESLICE) == 0) {
                        error = mbrinit(dev, info, sspp);
                        if (error != 0) {
                                dsgone(sspp);
                                return (error);
                        }
                }
                ssp = *sspp;
                ssp->dss_oflags = flags;

                /*
                 * If there are no real slices, then make the compatiblity
                 * slice cover the whole disk.
                 */
                if (ssp->dss_nslices == BASE_SLICE) {
                        sp = &ssp->dss_slices[COMPATIBILITY_SLICE];

                        sp->ds_size = info->d_media_blocks;
                        sp->ds_reserved = 0;
                }

                /*
                 * Set dss_first_bsd_slice to point at the first BSD
                 * slice, if any.
                 */
                for (slice = BASE_SLICE; slice < ssp->dss_nslices; slice++) {
                        sp = &ssp->dss_slices[slice];
                        if (sp->ds_type == DOSPTYP_386BSD /* XXX */) {
#if 0
                                struct diskslice *csp;
#endif

                                ssp->dss_first_bsd_slice = slice;
#if 0
                                /*
                                 * no longer supported, s0 is a real slice
                                 * for GPT
                                 */
                                csp = &ssp->dss_slices[COMPATIBILITY_SLICE];
                                csp->ds_offset = sp->ds_offset;
                                csp->ds_size = sp->ds_size;
                                csp->ds_type = sp->ds_type;
                                csp->ds_reserved = sp->ds_reserved;
#endif
                                break;
                        }
                }

                /*
                 * By definition accesses via the whole-disk device do not
                 * specify any reserved areas.  The whole disk may be read
                 * or written by the whole-disk device.
                 *
                 * ds_label for a whole-disk device is only used as a
                 * template.
                 */
                sp = &ssp->dss_slices[WHOLE_DISK_SLICE];
                sp->ds_label = clone_label(info, NULL);
                sp->ds_wlabel = TRUE;
                sp->ds_reserved = 0;
        }

        /*
         * Load the disklabel for the slice being accessed unless it is
         * a whole-disk-slice or a whole-slice-partition (as determined
         * by DSO_NOLABELS).
         *
         * We could scan all slices here and try to load up their
         * disklabels, but that would cause us to access slices that
         * the user may otherwise not intend us to access, or corrupted
         * slices, etc.
         *
         * XXX if there are no opens on the slice we may want to re-read
         * the disklabel anyway, even if we have one cached.
         */
        slice = dkslice(dev);
        if (slice >= ssp->dss_nslices)
                return (ENXIO);
        sp = &ssp->dss_slices[slice];
        part = dkpart(dev);

        if ((flags & DSO_NOLABELS) == 0 && sp->ds_label == NULL) {
                dev1 = dkmodslice(dkmodpart(dev, WHOLE_SLICE_PART), slice);

                /*
                 * If opening a raw disk we do not try to
                 * read the disklabel now.  No interpretation of raw disks
                 * (e.g. like 'da0') ever occurs.  We will try to read the
                 * disklabel for a raw slice if asked to via DIOC* ioctls.
                 *
                 * Access to the label area is disallowed by default.  Note
                 * however that accesses via WHOLE_DISK_SLICE, and accesses
                 * via WHOLE_SLICE_PART for slices without valid disklabels,
                 * will allow writes and ignore the flag.
                 */
                set_ds_wlabel(ssp, slice, FALSE);
                dsreadandsetlabel(dev1, flags, ssp, sp, info);
        }

        /*
         * If opening a particular partition the disklabel must exist and
         * the partition must be present in the label.
         *
         * If the partition is the special whole-disk-slice no partition
         * table need exist.
         */
        if (part != WHOLE_SLICE_PART && slice != WHOLE_DISK_SLICE) {
                if (sp->ds_label == NULL || part >= getnumparts(sp->ds_label))
                        return (EINVAL);
        }
        dssetmask(sp, part);

        /*
         * Do not allow special raw-extension partitions to be opened
         * if the device doesn't support them.  Raw-extension partitions
         * are typically used to handle CD tracks.
         */
        if (slice == WHOLE_DISK_SLICE && part >= 128 &&
            part != WHOLE_SLICE_PART) {
                if ((info->d_dsflags & DSO_RAWEXTENSIONS) == 0)
                        return (EINVAL);
        }
        return (0);
}

/*
 * Attempt to read the disklabel.  If successful, store it in sp->ds_label.
 *
 * If we cannot read the disklabel and DSO_COMPATLABEL is set, we construct
 * a fake label covering the whole disk.
 */
static
int
dsreadandsetlabel(cdev_t dev, u_int flags,
                  struct diskslices *ssp, struct diskslice *sp,
                  struct disk_info *info)
{
        struct disklabel *lp1;
        const char *msg;
        const char *sname;
        char partname[2];
        int slice = dkslice(dev);
        u_int64_t old_reserved;

        sname = dsname(dev, dkunit(dev), slice, WHOLE_SLICE_PART, partname);
        lp1 = clone_label(info, sp);
        old_reserved = sp->ds_reserved;
        sp->ds_reserved = 0;
        msg = readdisklabel(dev, lp1);
        sp->ds_reserved = old_reserved;

        if (msg != NULL && (flags & DSO_COMPATLABEL)) {
                msg = NULL;
                kfree(lp1, M_DEVBUF);
                lp1 = clone_label(info, sp);
        }
        if (msg == NULL)
                msg = fixlabel(sname, sp, lp1, FALSE);
        if (msg != NULL) {
                if (sp->ds_type == DOSPTYP_386BSD /* XXX */)
                        log(LOG_WARNING, "%s: cannot find label (%s)\n",
                            sname, msg);
                kfree(lp1, M_DEVBUF);
        } else {
                set_ds_label(ssp, slice, lp1);
                set_ds_wlabel(ssp, slice, FALSE);
        }
        return (msg ? EINVAL : 0);
}

int64_t
dssize(cdev_t dev, struct diskslices **sspp)
{
        struct disklabel *lp;
        int part;
        int slice;
        struct diskslices *ssp;
        u_int64_t start;
        u_int64_t blocks;

        slice = dkslice(dev);
        part = dkpart(dev);
        ssp = *sspp;
        if (ssp == NULL || slice >= ssp->dss_nslices
            || !dschkmask(&ssp->dss_slices[slice], part)) {
                if (dev_dopen(dev, FREAD, S_IFCHR, proc0.p_ucred) != 0)
                        return (-1);
                dev_dclose(dev, FREAD, S_IFCHR);
                ssp = *sspp;
        }
        lp = ssp->dss_slices[slice].ds_label;
        if (lp == NULL)
                return (-1);
        if (getpartbounds(lp, part, &start, &blocks))
                return (-1);
        return ((int64_t)blocks);
}

static void
free_ds_label(struct diskslices *ssp, int slice)
{
        struct disklabel *lp;
        struct diskslice *sp;

        sp = &ssp->dss_slices[slice];
        lp = sp->ds_label;
        if (lp == NULL)
                return;
        kfree(lp, M_DEVBUF);
        set_ds_label(ssp, slice, (struct disklabel *)NULL);
}

static void
set_ds_label(struct diskslices *ssp, int slice, struct disklabel *lp)
{
        struct diskslice *sp = &ssp->dss_slices[slice];

        sp->ds_label = lp;
        adjust_label_reserved(ssp, slice, sp);
}

static void
set_ds_wlabel(struct diskslices *ssp, int slice, int wlabel)
{
        ssp->dss_slices[slice].ds_wlabel = wlabel;
}