libdiskmgt/common/cache.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2002, 2012, Oracle and/or its affiliates. All rights reserved.
 */

#include <fcntl.h>
#include <libdevinfo.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libintl.h>
#include <synch.h>
#include <sys/sunddi.h>
#include <sys/types.h>
#include <libgen.h>
#include <syslog.h>

#include "libdiskmgt.h"
#include "disks_private.h"
#include "partition.h"

#define ALIASES     0
#define DEVPATHS    1

/*
 * Set DM_LIBDISKMGT_DEBUG in the environment.  Two levels of debugging:
 *    1 - errors, warnings and minimal tracing information
 *    2 - verbose information
 * All output prints on stderr.
 */
int dm_debug = 0;

/* Lock protecting the cached data */
static rwlock_t     cache_lock = DEFAULTRWLOCK;
static disk_t       *disk_listp = NULL;
static controller_t *controller_listp = NULL;
static bus_t        *bus_listp = NULL;
static int      cache_loaded = 0;

static rwlock_t     desc_lock = DEFAULTRWLOCK;
descriptor_t        *desc_listp = NULL;

static void     clear_descriptors(void *gp);
static void     clr_ctrl_disk_ptr(controller_t *cp, disk_t *dp);
static void     clr_path_disk_ptr(path_t *pp, disk_t *dp);
static void     del_drive(disk_t *dp);
static void     del_drive_by_name(char *name);
static descriptor_t *have_desc(int type, void *gp, char *name, char *mname);
static int      initialize();
static int      make_descriptors(int type);
static int      match_disk(disk_t *oldp, disk_t *newp);
static int      match_aliases(disk_t *d1p, disk_t *d2p);
static int      match_alias(alias_t *ap, alias_t *listp);
static descriptor_t *new_descriptor(dm_desc_type_t type, void *op,
                char *name, char *mname);
static void     rewalk_tree();
static void     update_desc(descriptor_t *descp, disk_t *newdisksp,
                controller_t *newctrlp, bus_t *newbusp);
static void     update_desc_busp(descriptor_t *descp, bus_t *busp);
static void     update_desc_ctrlp(descriptor_t *descp,
                controller_t *newstrlp);
static void     update_desc_diskp(descriptor_t *descp,
                disk_t *newdisksp);
static void     update_desc_pathp(descriptor_t *descp,
                controller_t *newctrlp);

/*
 * We only cache some of the data that we can obtain.  For much of the data
 * (e.g. slices & disks getting repartitioned) there are no events which would
 * enable us to cache.  As more events are added we can cache more information.
 *
 * Currently we cache the information we get from the dev tree walk.  This is
 * basically the information about the drives, aliases, devpaths, controllers
 * and paths.  We do not cache any information related to media, partitions
 * or slices.
 *
 * A fundamental part of the API design is that the application can hold on
 * to a set of descriptors for an indeterminate amount of time.  Even if the
 * application does not hold descriptors there is a window of time between the
 * call that gets the descriptor and the use of the descriptor to get more
 * information.  Because of this, the cache design must work even if the object
 * that the descriptor refers to no longer exists.
 *
 * Given this requirement, the code implements a two level cache.  The
 * descriptors that the application gets are really pointers into the first
 * level of the cache.  This first level contains the actual descriptors.
 * These descriptors in turn refer to the objects we build from the dev tree
 * walk which represent the drives and controllers.  This is the second level
 * in the cache.
 *
 * When we update the second level of the cache (the drives and controllers)
 * we go through the first level (the descriptors) and update the pointers
 * in those descriptors to refer to the new objects in the second level.  If
 * the object that the descriptor referred to is no longer in existence, we
 * just null out the pointer in the descriptor.  In this way the code that
 * uses the descriptors knows that the object referred to by the descriptor
 * no longer exists.
 *
 * We keep a reference count in the descriptors.  This is incremented when
 * we hand out a pointer to the descriptor and decremented when the application
 * frees the descriptor it has.  When the reference count goes to 0 we garbage
 * collect the descriptors.  In this way we only have to update active
 * descriptors when we refresh the cache after an event.
 *
 * An example of the flow when we create descriptors:
 *    dm_get_descriptors            libdiskmgt.c
 *  drive_get_descriptors           drive.c
 *      cache_get_descriptors       cache.c
 *      make_descriptors        cache.c
 *          drive_make_descriptors  drive.c
 *          cache_load_desc     cache.c
 *      {update refcnts on descriptors & return them}
 *
 * The idea behind cache_get_descriptors and cache_load_desc is that we
 * separate the act of making the descriptor within the cache (which requires
 * us to call back out to one of the object functions - drive_make_descriptors)
 * from the act of handing out the descriptor (which requires us to increment
 * the refcnt).  In this way we keep all of the refcnt handling centralized
 * in one function instead of forcing each object to ensure it replicates
 * the refcnt handling correctly.
 *
 * Descriptors use two different kinds of indrection to refer to their
 * corresponding object.  For objects we cache (controllers, paths & drives)
 * the descriptor keeps a pointer to that object.  For objects that we
 * dynamically build, the descriptor uses a combination of a pointer to the
 * base object (usually the drive) along with a name (e.g. the media name or
 * the alias).  For objects that are based on media (e.g. a slice) we actually
 * have to maintain a pointer (to the disk) and two names (e.g. the slice name
 * and the media name which is the secondary name).
 */

void
cache_free_alias(alias_t *aliasp)
{
    slice_t *dp;

    if (aliasp->alias_cxtydz != NULL)
        free(aliasp->alias_cxtydz);
    if (aliasp->alias_did != NULL)
        free(aliasp->alias_did);
    free(aliasp->kstat_name);
    free(aliasp->wwn);

    /* free devpaths */
    dp = aliasp->devpaths;
    while (dp != NULL) {
        slice_t *nextp;

        nextp = dp->next;
        free(dp->devpath);
        free(dp);
        dp = nextp;
    }

    /* free orig_paths */
    dp = aliasp->orig_paths;
    while (dp != NULL) {
    slice_t *nextp;

        nextp = dp->next;
        free(dp->devpath);
        free(dp);
        dp = nextp;
    }

    free(aliasp);
}

void
cache_free_bus(bus_t *bp)
{
    free(bp->name);
    free(bp->btype);
    free(bp->kstat_name);
    free(bp->pname);
    free(bp->controllers);
    free(bp);
}

void
cache_free_controller(controller_t *cp)
{
    free(cp->name);
    free(cp->kstat_name);
    free(cp->disks);
    if (cp->paths != NULL) {
        int i;

        for (i = 0; cp->paths[i]; i++) {
            /* free the path since it can't exist w/o the ctrlr */
            cache_free_path(cp->paths[i]);
        }
        free(cp->paths);
    }

    free(cp);
}

void
cache_free_descriptor(descriptor_t *desc)
{
    int locked;

    if (!cache_is_valid_desc(desc)) {
        return;
    }

    desc_wlock(&locked);
    desc->refcnt--;

    if (desc->refcnt <= 0) {
        free(desc->name);
        free(desc->secondary_name);
        if (desc->prev == NULL) {
            /* this is the first descriptor, update head ptr */
            desc_listp = desc->next;
        } else {
            desc->prev->next = desc->next;
        }
        if (desc->next != NULL) {
            desc->next->prev = desc->prev;
        }
        free(desc);
    }

    desc_unlock(&locked);
}

void
cache_free_descriptors(descriptor_t **desc_list)
{
    int i;

    for (i = 0; desc_list[i]; i++) {
        cache_free_descriptor(desc_list[i]);
    }

    free(desc_list);
}

void
cache_free_disk(disk_t *dp)
{
    alias_t *ap;

    free(dp->device_id);
    if (dp->devid != NULL) {
        devid_free(dp->devid);
    }
    free(dp->kernel_name);
    free(dp->product_id);
    free(dp->vendor_id);
    free(dp->controllers);
    /* the path objects are freed when we free the controller */
    free(dp->paths);
    ap = dp->aliases;
    while (ap != NULL) {
        alias_t *nextp;

        nextp = ap->next;
        cache_free_alias(ap);
        ap = nextp;
    }

    free(dp);
}

void
cache_free_path(path_t *pp)
{
    free(pp->name);
    free(pp->disks);
    free(pp->states);

    if (pp->wwns) {
        int i;

        for (i = 0; pp->wwns[i]; i++) {
            free(pp->wwns[i]);
        }
        free(pp->wwns);
    }

    free(pp);
}

bus_t *
cache_get_buslist()
{
    if (initialize() != 0) {
        return (NULL);
    }

    return (bus_listp);
}

controller_t *
cache_get_controllerlist()
{
    if (initialize() != 0) {
        return (NULL);
    }

    return (controller_listp);
}

/*
 * This routine will either get the existing descriptor from the descriptor
 * cache or make make a new descriptor and put it in the descriptor cache and
 * return a pointer to that descriptor.  We increment the refcnt when we hand
 * out the descriptor.
 */
descriptor_t *
cache_get_desc(int type, void *gp, char *name, char *secondary_name, int *errp)
{
    descriptor_t    *dp;

    *errp = 0;
    if ((dp = have_desc(type, gp, name, secondary_name)) == NULL) {
        /* make a new desc */
        if ((dp = new_descriptor(type, gp, name, secondary_name))
            == NULL) {
            *errp = ENOMEM;
        }
    }

    if (dp != NULL) {
        dp->refcnt++;
    }

    return (dp);
}

descriptor_t **
cache_get_descriptors(int type, int *errp)
{
    descriptor_t    **descs;
    descriptor_t    *descp;
    int     cnt = 0;
    int     pos;
    int     locked;

    if ((*errp = make_descriptors(type)) != 0) {
        return (NULL);
    }

    desc_rlock(&locked);
    /* count the number of active descriptors in the descriptor cache */
    descp = desc_listp;
    while (descp != NULL) {
        if (descp->type == type && descp->p.generic != NULL) {
            cnt++;
        }
        descp = descp->next;
    }

    descs = (descriptor_t **)calloc(cnt + 1, sizeof (descriptor_t *));
    if (descs == NULL) {
        desc_unlock(&locked);
        *errp = ENOMEM;
        return (NULL);
    }

    pos = 0;
    descp = desc_listp;
    while (descp != NULL) {
        if (descp->type == type && descp->p.generic != NULL) {
            /* update refcnts before handing out the descriptors */
            descp->refcnt++;
            descs[pos++] = descp;
        }
        descp = descp->next;
    }
    descs[pos] = NULL;

    desc_unlock(&locked);
    *errp = 0;
    return (descs);
}

disk_t *
cache_get_disklist()
{
    if (initialize() != 0) {
        return (NULL);
    }

    return (disk_listp);
}

int
cache_is_valid_desc(descriptor_t *d)
{
    descriptor_t    *descp;
    int     valid = 0;
    int     locked;

    desc_rlock(&locked);
    for (descp = desc_listp; descp != NULL; descp = descp->next) {
        if ((valid = (descp == d)) != 0)
            break;
    }
    desc_unlock(&locked);

    return (valid);
}

/*
 * This function is called by the *_make_descriptors function
 * (e.g. drive_make_descriptors) within each of the objects.  This function
 * makes sure that the descriptor is built in the descriptor cache but
 * it does not hand out the descriptors, so the refcnt is never incremented.
 */
void
cache_load_desc(int type, void *gp, char *name, char *secondary_name, int *errp)
{
    *errp = 0;
    if (have_desc(type, gp, name, secondary_name) == NULL) {
        /* make a new desc */
        if (new_descriptor(type, gp, name, secondary_name) == NULL) {
            *errp = ENOMEM;
        }
    }
}

void
cache_rlock(int *state)
{
    if (RW_READ_HELD(&cache_lock) || RW_WRITE_HELD(&cache_lock))
        *state = 0;
    else if (rw_rdlock(&cache_lock) == 0)
        *state = 1;
    else
        abort();
}

void
cache_wlock(int *state)
{
    if (RW_WRITE_HELD(&cache_lock))
        *state = 0;
    else if (rw_wrlock(&cache_lock) == 0)
        *state = 1;
    else
        abort();
}

void
cache_unlock(int *state)
{
    if (*state == 1) {
        (void) rw_unlock(&cache_lock);
        *state = 0;
    }
}

void
desc_rlock(int *state)
{
    if (RW_READ_HELD(&desc_lock) || RW_WRITE_HELD(&desc_lock))
        *state = 0;
    else if (rw_rdlock(&desc_lock) == 0)
        *state = 1;
    else
        abort();
}

void
desc_wlock(int *state)
{
    if (RW_WRITE_HELD(&desc_lock))
        *state = 0;
    else if (rw_wrlock(&desc_lock) == 0)
        *state = 1;
    else
        abort();
}

void
desc_unlock(int *state)
{
    if (*state == 1) {
        (void) rw_unlock(&desc_lock);
        *state = 0;
    }
}

/*
 * This function is called when we get a devtree event.  Type is either add
 * or delete of a drive.
 *
 * For delete, we need to clean up the 2nd level structures and clean up
 * the pointers between the them.  We also clear the descriptor ptr.
 */
void
dm_cache_update(dm_event_type_t ev_type, char *devname)
{
    char *orig_name;
    int clocked;
    int dlocked;

    cache_wlock(&clocked);
    desc_wlock(&dlocked);

    /* update the cache */
    switch (ev_type) {
    case DM_EV_DISK_ADD:
        rewalk_tree();
        events_new_event(devname, DM_DRIVE, DM_EV_TADD);
        break;
    case DM_EV_DISK_DELETE:
        orig_name = devname;
        devname = basename(devname);
        del_drive_by_name(devname);
        events_new_event(orig_name, DM_DRIVE, DM_EV_TREMOVE);
        break;
    }

    libdiskmgt_destroy_inuse_cache();

    desc_unlock(&dlocked);
    cache_unlock(&clocked);
}

/*
 * Clear any descriptors that point at the specified cached object.
 * We must go through the whole list since there can be multiple descriptors
 * referencing the same object (i.e. drive/media/slice descriptors all point
 * to the same drive object).  The list is usually small (0 size) so this
 * is not a big deal.
 */
static void
clear_descriptors(void *gp)
{
    descriptor_t    *descp;
    int     locked;

    desc_wlock(&locked);
    for (descp = desc_listp; descp != NULL; descp = descp->next) {
        if (descp->p.generic == gp) {
            /* clear descriptor */
            descp->p.generic = NULL;
        }
    }
    desc_unlock(&locked);
}

/* remove the ptr from the controller to the specified disk */
static void
clr_ctrl_disk_ptr(controller_t *cp, disk_t *dp)
{
    int i;

    for (i = 0; cp->disks[i]; i++) {
        if (dp == cp->disks[i]) {
            int j;

            for (j = i; cp->disks[j]; j++) {
                cp->disks[j] = cp->disks[j + 1];
            }
            return;
        }
    }
}

/* remove the ptr from the path to the specified disk */
static void
clr_path_disk_ptr(path_t *pp, disk_t *dp)
{
    int i;

    for (i = 0; pp->disks[i]; i++) {
        if (dp == pp->disks[i]) {
            int j;

            for (j = i; pp->disks[j]; j++) {
                pp->disks[j] = pp->disks[j + 1];
            }
            return;
        }
    }
}

static void
del_drive(disk_t *dp)
{
    int i;
    disk_t  *listp;
    disk_t  *prev = NULL;

    clear_descriptors(dp);

    /* clear any ptrs from controllers to this drive */
    if (dp->controllers != NULL) {
        for (i = 0; dp->controllers[i]; i++) {
            clr_ctrl_disk_ptr(dp->controllers[i], dp);
        }
    }

    /* clear any ptrs from paths to this drive */
    if (dp->paths != NULL) {
        for (i = 0; dp->paths[i]; i++) {
            clr_path_disk_ptr(dp->paths[i], dp);
        }
    }

    /* clear drive from disk list */
    for (listp = disk_listp; listp != NULL; listp = listp->next) {
        if (dp == listp) {
            if (prev == NULL) {
                disk_listp = dp->next;
            } else {
                prev->next = dp->next;
            }

            break;
        }

        if (prev == NULL) {
            prev = disk_listp;
        } else {
            prev = prev->next;
        }
    }

    cache_free_disk(dp);
}

/*
 * Delete cached drive info when we get a devtree drive delete event.
 */
static void
del_drive_by_name(char *name)
{
    disk_t  *listp;

    for (listp = disk_listp; listp != NULL; listp = listp->next) {
        alias_t *ap;

        for (ap = listp->aliases; ap; ap = ap->next) {
            if (libdiskmgt_str_eq(name, ap->alias_cxtydz) ||
                libdiskmgt_str_eq(name, ap->alias_did)) {
                del_drive(listp);
                return;
            }
        }
    }
}

static descriptor_t *
have_desc(int type, void *gp, char *name, char *secondary_name)
{
    descriptor_t    *descp;
    int     locked;

    if (name != NULL && name[0] == 0) {
        name = NULL;
    }

    if (secondary_name != NULL && secondary_name[0] == 0) {
        secondary_name = NULL;
    }

    desc_rlock(&locked);
    descp = desc_listp;
    while (descp != NULL) {
        if (descp->type == type && descp->p.generic == gp &&
            libdiskmgt_str_eq(descp->name, name)) {
            if (type == DM_SLICE || type == DM_PARTITION ||
                type == DM_PATH)
                if (libdiskmgt_str_eq(descp->secondary_name,
                    secondary_name))
                    break;
            else
                break;
        }
        descp = descp->next;
    }
    desc_unlock(&locked);

    return (descp);
}

static int
initialize()
{
    struct search_args  args;

    if (cache_loaded) {
        return (0);
    }

    libdiskmgt_init_debug();

    findevs(&args);

    if (args.dev_walk_status != 0) {
        return (args.dev_walk_status);
    }

    disk_listp = args.disk_listp;
    controller_listp = args.controller_listp;
    bus_listp = args.bus_listp;

    cache_loaded = 1;

    /*
     * Only start the event thread if we are not doing an install
     */
    if (getenv("_LIBDISKMGT_INSTALL") == NULL) {
        if (events_start_event_watcher() != 0) {
            /*
             * Log a message about the failure to start
             * sysevents and continue on.
             */
            syslog(LOG_WARNING, dgettext(TEXT_DOMAIN,
                "libdiskmgt: sysevent thread for cache "
                "events failed to start\n"));
        }
    }
    return (0);
}

static int
make_descriptors(int type)
{
    int error;

    if ((error = initialize()) != 0) {
        return (error);
    }

    switch (type) {
    case DM_DRIVE:
        error = drive_make_descriptors();
        break;
    case DM_BUS:
        error = bus_make_descriptors();
        break;
    case DM_CONTROLLER:
        error = controller_make_descriptors();
        break;
    case DM_PATH:
        error = path_make_descriptors();
        break;
    case DM_ALIAS:
        error = alias_make_descriptors();
        break;
    case DM_MEDIA:
        error = media_make_descriptors();
        break;
    case DM_PARTITION:
        error = partition_make_descriptors();
        break;
    case DM_SLICE:
        error = slice_make_descriptors();
        break;
    }

    return (error);
}

static int
match_alias(alias_t *ap, alias_t *listp)
{
    if ((ap->alias_cxtydz == NULL) && (ap->alias_did == NULL)) {
        return (0);
    }

    while (listp != NULL) {
        if (libdiskmgt_str_eq(ap->alias_cxtydz, listp->alias_cxtydz) ||
            libdiskmgt_str_eq(ap->alias_cxtydz, listp->alias_did) ||
            libdiskmgt_str_eq(ap->alias_did, listp->alias_cxtydz) ||
            libdiskmgt_str_eq(ap->alias_did, listp->alias_did)) {
            return (1);
        }
        listp = listp->next;
    }

    return (0);
}

static int
match_aliases(disk_t *d1p, disk_t *d2p)
{
    alias_t *ap;

    if (d1p->aliases == NULL || d2p->aliases == NULL) {
        return (0);
    }

    ap = d1p->aliases;
    while (ap != NULL) {
        if (match_alias(ap, d2p->aliases)) {
            return (1);
        }
        ap = ap->next;
    }

    return (0);
}

static int
match_disk(disk_t *oldp, disk_t *newp)
{
    if (oldp->devid != NULL) {
        if (newp->devid != NULL &&
            devid_compare(oldp->devid, newp->devid) == 0) {
            return (1);
        }

    } else {
        /* oldp device id is null */
        if (newp->devid == NULL) {
            /* both disks have no device id, check aliases */
            if (match_aliases(oldp, newp)) {
                return (1);
            }
        }
    }

    return (0);
}

static descriptor_t *
new_descriptor(dm_desc_type_t type, void *op, char *name, char *secondary_name)
{
    descriptor_t    *d;
    int     locked;

    if (name != NULL && name[0] == 0) {
        name = NULL;
    }

    if (secondary_name != NULL && secondary_name[0] == 0) {
        secondary_name = NULL;
    }

    d = (descriptor_t *)malloc(sizeof (descriptor_t));
    if (d == NULL) {
        return (NULL);
    }
    d->type = type;
    switch (type) {
    case DM_CONTROLLER:
        d->p.controller = op;
        break;
    case DM_BUS:
        d->p.bus = op;
        break;
    default:
        d->p.disk = op;
        break;
    }
    if (name != NULL) {
        d->name = strdup(name);
        if (d->name == NULL) {
            free(d);
            return (NULL);
        }
    } else {
        d->name = NULL;
    }

    if (type == DM_SLICE || type == DM_PARTITION) {
        if (secondary_name != NULL) {
            d->secondary_name = strdup(secondary_name);
            if (d->secondary_name == NULL) {
                free(d->name);
                free(d);
                return (NULL);
            }
        } else {
            d->secondary_name = NULL;
        }
    } else {
        d->secondary_name = NULL;
    }

    d->refcnt = 0;

    desc_wlock(&locked);
    /* add this descriptor to the head of the list */
    if (desc_listp != NULL) {
        desc_listp->prev = d;
    }
    d->prev = NULL;
    d->next = desc_listp;
    desc_listp = d;
    desc_unlock(&locked);

    return (d);
}

static void
rewalk_tree()
{
    struct search_args  args;
    disk_t          *free_disklistp;
    controller_t        *free_controllerlistp;
    bus_t           *free_buslistp;

    findevs(&args);

    if (args.dev_walk_status == 0) {
        descriptor_t    *descp;

        /* walk the existing descriptors and update the ptrs */
        descp = desc_listp;
        while (descp != NULL) {
            update_desc(descp, args.disk_listp,
                args.controller_listp, args.bus_listp);
            descp = descp->next;
        }

        /* update the cached object ptrs */
        free_disklistp = disk_listp;
        free_controllerlistp = controller_listp;
        free_buslistp = bus_listp;
        disk_listp = args.disk_listp;
        controller_listp = args.controller_listp;
        bus_listp = args.bus_listp;

    } else {
        free_disklistp = args.disk_listp;
        free_controllerlistp = args.controller_listp;
        free_buslistp = args.bus_listp;
    }

    /*
     * Free the memory from either the old cached objects or the failed
     * update objects.
     */
    while (free_disklistp != NULL) {
        disk_t *nextp;

        nextp = free_disklistp->next;
        cache_free_disk(free_disklistp);
        free_disklistp = nextp;
    }
    while (free_controllerlistp != NULL) {
        controller_t *nextp;

        nextp = free_controllerlistp->next;
        cache_free_controller(free_controllerlistp);
        free_controllerlistp = nextp;
    }
    while (free_buslistp != NULL) {
        bus_t *nextp;

        nextp = free_buslistp->next;
        cache_free_bus(free_buslistp);
        free_buslistp = nextp;
    }
}

/*
 * Walk the new set of cached objects and update the descriptor ptr to point
 * to the correct new object.  If there is no object any more, set the desc
 * ptr to null.
 */
static void
update_desc(descriptor_t *descp, disk_t *newdisksp, controller_t *newctrlp,
    bus_t *newbusp)
{
    /* if the descriptor is already dead, we're done */
    if (descp->p.generic == NULL) {
        return;
    }

    /*
     * All descriptors use a disk ptr except for controller descriptors
     * and path descriptors.
     */

    switch (descp->type) {
    case DM_BUS:
        update_desc_busp(descp, newbusp);
        break;
    case DM_CONTROLLER:
        update_desc_ctrlp(descp, newctrlp);
        break;
    case DM_PATH:
        update_desc_pathp(descp, newctrlp);
        break;
    default:
        update_desc_diskp(descp, newdisksp);
        break;
    }
}

static void
update_desc_busp(descriptor_t *descp, bus_t *busp)
{
    /* walk the new objects and find the correct bus */
    for (; busp; busp = busp->next) {
        if (libdiskmgt_str_eq(descp->p.bus->name, busp->name)) {
            descp->p.bus = busp;
            return;
        }
    }

    /* we did not find the controller any more, clear the ptr in the desc */
    descp->p.bus = NULL;
}

static void
update_desc_ctrlp(descriptor_t *descp, controller_t *newctrlp)
{
    /* walk the new objects and find the correct controller */
    for (; newctrlp; newctrlp = newctrlp->next) {
        if (libdiskmgt_str_eq(descp->p.controller->name,
            newctrlp->name)) {
            descp->p.controller = newctrlp;
            return;
        }
    }

    /* we did not find the controller any more, clear the ptr in the desc */
    descp->p.controller = NULL;
}

static void
update_desc_diskp(descriptor_t *descp, disk_t *newdisksp)
{
    /* walk the new objects and find the correct disk */
    for (; newdisksp; newdisksp = newdisksp->next) {
        if (match_disk(descp->p.disk, newdisksp)) {
            descp->p.disk = newdisksp;
            return;
        }
    }

    /* we did not find the disk any more, clear the ptr in the descriptor */
    descp->p.disk = NULL;
}

static void
update_desc_pathp(descriptor_t *descp, controller_t *newctrlp)
{
    /* walk the new objects and find the correct path */
    for (; newctrlp; newctrlp = newctrlp->next) {
        path_t  **pp;

        pp = newctrlp->paths;
        if (pp != NULL) {
            int i;

            for (i = 0; pp[i]; i++) {
                if (libdiskmgt_str_eq(descp->p.path->name,
                    pp[i]->name)) {
                    descp->p.path = pp[i];
                    return;
                }
            }
        }
    }

    /* we did not find the path any more, clear the ptr in the desc */
    descp->p.path = NULL;
}