/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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.
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/errno.h>
#include <sys/jail.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/rmlock.h>
#include <sys/sx.h>
#include <sys/queue.h>
#include <sys/proc.h>
#include <sys/osd.h>

/* OSD (Object Specific Data) */

/*
 * Lock key:
 *  (m) osd_module_lock
 *  (o) osd_object_lock
 *  (l) osd_list_lock
 */
struct osd_master {
	struct sx		 osd_module_lock;
	struct rmlock		 osd_object_lock;
	struct mtx		 osd_list_lock;
	LIST_HEAD(, osd)	 osd_list;		/* (l) */
	osd_destructor_t	*osd_destructors;	/* (o) */
	osd_method_t		*osd_methods;		/* (m) */
	u_int			 osd_ntslots;		/* (m) */
	const u_int		 osd_nmethods;
};

static MALLOC_DEFINE(M_OSD, "osd", "Object Specific Data");

static int osd_debug = 0;
SYSCTL_INT(_debug, OID_AUTO, osd, CTLFLAG_RWTUN, &osd_debug, 0, "OSD debug level");

#define	OSD_DEBUG(...)	do {						\
	if (osd_debug) {						\
		printf("OSD (%s:%u): ", __func__, __LINE__);		\
		printf(__VA_ARGS__);					\
		printf("\n");						\
	}								\
} while (0)

static void do_osd_del(u_int type, struct osd *osd, u_int slot,
    int list_locked);

/*
 * List of objects with OSD.
 */
struct osd_master osdm[OSD_LAST + 1] = {
	[OSD_JAIL] = { .osd_nmethods = PR_MAXMETHOD },
};

static void
osd_default_destructor(void *value __unused)
{
	/* Do nothing. */
}

int
osd_register(u_int type, osd_destructor_t destructor, osd_method_t *methods)
{
	void *newptr;
	u_int i, m;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));

	/*
	 * If no destructor is given, use default one. We need to use some
	 * destructor, because NULL destructor means unused slot.
	 */
	if (destructor == NULL)
		destructor = osd_default_destructor;

	sx_xlock(&osdm[type].osd_module_lock);
	/*
	 * First, we try to find unused slot.
	 */
	for (i = 0; i < osdm[type].osd_ntslots; i++) {
		if (osdm[type].osd_destructors[i] == NULL) {
			OSD_DEBUG("Unused slot found (type=%u, slot=%u).",
			    type, i + 1);
			break;
		}
	}
	/*
	 * If no unused slot was found, allocate one.
	 */
	if (i == osdm[type].osd_ntslots) {
		osdm[type].osd_ntslots++;
		if (osdm[type].osd_nmethods != 0)
			osdm[type].osd_methods = realloc(osdm[type].osd_methods,
			    sizeof(osd_method_t) * osdm[type].osd_ntslots *
			    osdm[type].osd_nmethods, M_OSD, M_WAITOK);
		newptr = malloc(sizeof(osd_destructor_t) *
		    osdm[type].osd_ntslots, M_OSD, M_WAITOK);
		rm_wlock(&osdm[type].osd_object_lock);
		bcopy(osdm[type].osd_destructors, newptr,
		    sizeof(osd_destructor_t) * i);
		free(osdm[type].osd_destructors, M_OSD);
		osdm[type].osd_destructors = newptr;
		rm_wunlock(&osdm[type].osd_object_lock);
		OSD_DEBUG("New slot allocated (type=%u, slot=%u).",
		    type, i + 1);
	}

	osdm[type].osd_destructors[i] = destructor;
	if (osdm[type].osd_nmethods != 0) {
		for (m = 0; m < osdm[type].osd_nmethods; m++)
			osdm[type].osd_methods[i * osdm[type].osd_nmethods + m]
			    = methods != NULL ? methods[m] : NULL;
	}
	sx_xunlock(&osdm[type].osd_module_lock);
	return (i + 1);
}

void
osd_deregister(u_int type, u_int slot)
{
	struct osd *osd, *tosd;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
	KASSERT(slot > 0, ("Invalid slot."));

	sx_xlock(&osdm[type].osd_module_lock);
	rm_wlock(&osdm[type].osd_object_lock);
	KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

	/*
	 * Free all OSD for the given slot.
	 */
	mtx_lock(&osdm[type].osd_list_lock);
	LIST_FOREACH_SAFE(osd, &osdm[type].osd_list, osd_next, tosd)
		do_osd_del(type, osd, slot, 1);
	mtx_unlock(&osdm[type].osd_list_lock);

	/*
	 * Set destructor to NULL to free the slot.  We don't bother actually
	 * freeing any memory here because we'll gracefully reuse any freed
	 * slots, and reallocating the arrays as a smaller chunk of memory isn't
	 * actually guaranteed to succeed.  As such, we'll err on the side of
	 * caution and just leave it be since these are generally modestly sized
	 * allocations.
	 */
	osdm[type].osd_destructors[slot - 1] = NULL;
	OSD_DEBUG("Slot deregistration (type=%u, slot=%u).", type, slot);

	rm_wunlock(&osdm[type].osd_object_lock);
	sx_xunlock(&osdm[type].osd_module_lock);
}

int
osd_set(u_int type, struct osd *osd, u_int slot, void *value)
{

	return (osd_set_reserved(type, osd, slot, NULL, value));
}

void **
osd_reserve(u_int slot)
{

	KASSERT(slot > 0, ("Invalid slot."));

	OSD_DEBUG("Reserving slot array (slot=%u).", slot);
	return (malloc(sizeof(void *) * slot, M_OSD, M_WAITOK | M_ZERO));
}

int
osd_set_reserved(u_int type, struct osd *osd, u_int slot, void **rsv,
    void *value)
{
	struct rm_priotracker tracker;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
	KASSERT(slot > 0, ("Invalid slot."));

	rm_rlock(&osdm[type].osd_object_lock, &tracker);
	KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

	if (slot > osd->osd_nslots) {
		void **newptr;

		if (value == NULL) {
			OSD_DEBUG(
			    "Not allocating null slot (type=%u, slot=%u).",
			    type, slot);
			rm_runlock(&osdm[type].osd_object_lock, &tracker);
			if (rsv)
				osd_free_reserved(rsv);
			return (0);
		}

		/*
		 * Too few slots allocated here, so we need to extend or create
		 * the array.
		 */
		if (rsv) {
			/*
			 * Use the reserve passed in (assumed to be
			 * the right size).
			 */
			newptr = rsv;
			if (osd->osd_nslots != 0) {
				memcpy(newptr, osd->osd_slots,
				    sizeof(void *) * osd->osd_nslots);
				free(osd->osd_slots, M_OSD);
			}
		} else {
			newptr = realloc(osd->osd_slots, sizeof(void *) * slot,
			    M_OSD, M_NOWAIT | M_ZERO);
			if (newptr == NULL) {
				rm_runlock(&osdm[type].osd_object_lock,
				    &tracker);
				return (ENOMEM);
			}
		}
		if (osd->osd_nslots == 0) {
			/*
			 * First OSD for this object, so we need to put it
			 * onto the list.
			 */
			mtx_lock(&osdm[type].osd_list_lock);
			LIST_INSERT_HEAD(&osdm[type].osd_list, osd, osd_next);
			mtx_unlock(&osdm[type].osd_list_lock);
			OSD_DEBUG("Setting first slot (type=%u).", type);
		} else
			OSD_DEBUG("Growing slots array (type=%u).", type);
		osd->osd_slots = newptr;
		osd->osd_nslots = slot;
	} else if (rsv)
		osd_free_reserved(rsv);
	OSD_DEBUG("Setting slot value (type=%u, slot=%u, value=%p).", type,
	    slot, value);
	osd->osd_slots[slot - 1] = value;
	rm_runlock(&osdm[type].osd_object_lock, &tracker);
	return (0);
}

void
osd_free_reserved(void **rsv)
{

	OSD_DEBUG("Discarding reserved slot array.");
	free(rsv, M_OSD);
}

void *
osd_get_unlocked(u_int type, struct osd *osd, u_int slot)
{
	void *value;

	KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

	if (slot > osd->osd_nslots) {
		value = NULL;
		OSD_DEBUG("Slot doesn't exist (type=%u, slot=%u).", type, slot);
	} else {
		value = atomic_load_ptr(&osd->osd_slots[slot - 1]);
		OSD_DEBUG("Returning slot value (type=%u, slot=%u, value=%p).",
		    type, slot, value);
	}
	return (value);
}

void *
osd_get(u_int type, struct osd *osd, u_int slot)
{
	struct rm_priotracker tracker;
	void *value;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
	KASSERT(slot > 0, ("Invalid slot."));

	rm_rlock(&osdm[type].osd_object_lock, &tracker);
	value = osd_get_unlocked(type, osd, slot);
	rm_runlock(&osdm[type].osd_object_lock, &tracker);
	return (value);
}

void
osd_del(u_int type, struct osd *osd, u_int slot)
{
	struct rm_priotracker tracker;

	rm_rlock(&osdm[type].osd_object_lock, &tracker);
	do_osd_del(type, osd, slot, 0);
	rm_runlock(&osdm[type].osd_object_lock, &tracker);
}

static void
do_osd_del(u_int type, struct osd *osd, u_int slot, int list_locked)
{
	int i;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
	KASSERT(slot > 0, ("Invalid slot."));
	KASSERT(osdm[type].osd_destructors[slot - 1] != NULL, ("Unused slot."));

	OSD_DEBUG("Deleting slot (type=%u, slot=%u).", type, slot);

	if (slot > osd->osd_nslots) {
		OSD_DEBUG("Slot doesn't exist (type=%u, slot=%u).", type, slot);
		return;
	}
	if (osd->osd_slots[slot - 1] != NULL) {
		osdm[type].osd_destructors[slot - 1](osd->osd_slots[slot - 1]);
		osd->osd_slots[slot - 1] = NULL;
	}
	for (i = osd->osd_nslots - 1; i >= 0; i--) {
		if (osd->osd_slots[i] != NULL) {
			OSD_DEBUG("Slot still has a value (type=%u, slot=%u).",
			    type, i + 1);
			break;
		}
	}
	if (i == -1) {
		/* No values left for this object. */
		OSD_DEBUG("No more slots left (type=%u).", type);
		if (!list_locked)
			mtx_lock(&osdm[type].osd_list_lock);
		LIST_REMOVE(osd, osd_next);
		if (!list_locked)
			mtx_unlock(&osdm[type].osd_list_lock);
		free(osd->osd_slots, M_OSD);
		osd->osd_slots = NULL;
		osd->osd_nslots = 0;
	} else if (slot == osd->osd_nslots) {
		/* This was the last slot. */
		osd->osd_slots = realloc(osd->osd_slots,
		    sizeof(void *) * (i + 1), M_OSD, M_NOWAIT | M_ZERO);
		/*
		 * We always reallocate to smaller size, so we assume it will
		 * always succeed.
		 */
		KASSERT(osd->osd_slots != NULL, ("realloc() failed"));
		osd->osd_nslots = i + 1;
		OSD_DEBUG("Reducing slots array to %u (type=%u).",
		    osd->osd_nslots, type);
	}
}

int
osd_call(u_int type, u_int method, void *obj, void *data)
{
	osd_method_t methodfun;
	int error, i;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));
	KASSERT(method < osdm[type].osd_nmethods, ("Invalid method."));

	/*
	 * Call this method for every slot that defines it, stopping if an
	 * error is encountered.
	 */
	error = 0;
	sx_slock(&osdm[type].osd_module_lock);
	for (i = 0; i < osdm[type].osd_ntslots; i++) {
		/* Hole in the slot map; avoid dereferencing. */
		if (osdm[type].osd_destructors[i] == NULL)
			continue;
		methodfun = osdm[type].osd_methods[i * osdm[type].osd_nmethods +
		    method];
		if (methodfun != NULL && (error = methodfun(obj, data)) != 0)
			break;
	}
	sx_sunlock(&osdm[type].osd_module_lock);
	return (error);
}

void
osd_exit(u_int type, struct osd *osd)
{
	struct rm_priotracker tracker;
	u_int i;

	KASSERT(type >= OSD_FIRST && type <= OSD_LAST, ("Invalid type."));

	if (osd->osd_nslots == 0) {
		KASSERT(osd->osd_slots == NULL, ("Non-null osd_slots."));
		/* No OSD attached, just leave. */
		return;
	}

	rm_rlock(&osdm[type].osd_object_lock, &tracker);
	for (i = 1; i <= osd->osd_nslots; i++) {
		if (osdm[type].osd_destructors[i - 1] != NULL)
			do_osd_del(type, osd, i, 0);
		else
			OSD_DEBUG("Unused slot (type=%u, slot=%u).", type, i);
	}
	rm_runlock(&osdm[type].osd_object_lock, &tracker);
	OSD_DEBUG("Object exit (type=%u).", type);
}

static void
osd_init(void *arg __unused)
{
	u_int i;

	for (i = OSD_FIRST; i <= OSD_LAST; i++) {
		sx_init(&osdm[i].osd_module_lock, "osd_module");
		rm_init(&osdm[i].osd_object_lock, "osd_object");
		mtx_init(&osdm[i].osd_list_lock, "osd_list", NULL, MTX_DEF);
		LIST_INIT(&osdm[i].osd_list);
		osdm[i].osd_destructors = NULL;
		osdm[i].osd_ntslots = 0;
		osdm[i].osd_methods = NULL;
	}
}
SYSINIT(osd, SI_SUB_LOCK, SI_ORDER_ANY, osd_init, NULL);