/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2017, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ldlm/ldlm_inodebits.c
 *
 * Author: Peter Braam <braam@clusterfs.com>
 * Author: Phil Schwan <phil@clusterfs.com>
 */

/**
 * This file contains implementation of IBITS lock type
 *
 * IBITS lock type contains a bit mask determining various properties of an
 * object. The meanings of specific bits are specific to the caller and are
 * opaque to LDLM code.
 *
 * Locks with intersecting bitmasks and conflicting lock modes (e.g.  LCK_PW)
 * are considered conflicting.  See the lock mode compatibility matrix
 * in lustre_dlm.h.
 */

#define DEBUG_SUBSYSTEM S_LDLM

#include <lustre_dlm.h>
#include <obd_support.h>
#include <lustre_lib.h>
#include <obd_class.h>

#include "ldlm_internal.h"

#ifdef HAVE_SERVER_SUPPORT

/**
 * It should iterate through all waiting locks on a given resource queue and
 * attempt to grant them. An optimization is to check only heads waitintg
 * locks for each inodebit type.
 *
 * Must be called with resource lock held.
 */
int ldlm_reprocess_inodebits_queue(struct ldlm_resource *res,
				   struct list_head *queue,
				   struct list_head *work_list,
				   enum ldlm_process_intention intention,
				   struct ldlm_lock *hint)
{
	__u64 flags;
	int rc = LDLM_ITER_CONTINUE;
	enum ldlm_error err;
	LIST_HEAD(bl_ast_list);
	struct ldlm_ibits_queues *queues = res->lr_ibits_queues;
	int i;

	ENTRY;

	check_res_locked(res);

	LASSERT(res->lr_type == LDLM_IBITS);
	LASSERT(intention == LDLM_PROCESS_RESCAN ||
		intention == LDLM_PROCESS_RECOVERY);

	if (intention == LDLM_PROCESS_RECOVERY)
		return ldlm_reprocess_queue(res, queue, work_list, intention,
					    NULL);

restart:
	CDEBUG(D_DLMTRACE, "--- Reprocess resource "DLDLMRES" (%p)\n",
	       PLDLMRES(res), res);

	for (i = 0; i < MDS_INODELOCK_NUMBITS; i++) {
		LIST_HEAD(rpc_list);
		struct list_head *head = &queues->liq_waiting[i];
		struct ldlm_lock *pending;
		struct ldlm_ibits_node *node;

		if (list_empty(head))
			continue;
		if (hint && !(hint->l_policy_data.l_inodebits.bits & (1 << i)))
			continue;

		node = list_entry(head->next, struct ldlm_ibits_node,
				  lin_link[i]);

		pending = node->lock;
		LDLM_DEBUG(pending, "Reprocessing lock from queue %d", i);

		flags = 0;
		rc = ldlm_process_inodebits_lock(pending, &flags, intention,
						 &err, &rpc_list);
		if (ldlm_is_granted(pending)) {
			list_splice(&rpc_list, work_list);
			/* Try to grant more locks from current queue */
			i--;
		} else {
			list_splice(&rpc_list, &bl_ast_list);
		}
	}

	if (!list_empty(&bl_ast_list)) {
		unlock_res(res);

		rc = ldlm_run_ast_work(ldlm_res_to_ns(res), &bl_ast_list,
				       LDLM_WORK_BL_AST);

		lock_res(res);
		if (rc == -ERESTART)
			GOTO(restart, rc);
	}

	if (!list_empty(&bl_ast_list))
		ldlm_discard_bl_list(&bl_ast_list);

	RETURN(rc);
}

/**
 * Determine if the lock is compatible with all locks on the queue.
 *
 * If \a work_list is provided, conflicting locks are linked there.
 * If \a work_list is not provided, we exit this function on first conflict.
 *
 * \retval 0 if there are conflicting locks in the \a queue
 * \retval 1 if the lock is compatible to all locks in \a queue
 *
 * IBITS locks in granted queue are organized in bunches of
 * same-mode/same-bits locks called "skip lists". The First lock in the
 * bunch contains a pointer to the end of the bunch.  This allows us to
 * skip an entire bunch when iterating the list in search for conflicting
 * locks if first lock of the bunch is not conflicting with us.
 */
static int
ldlm_inodebits_compat_queue(struct list_head *queue, struct ldlm_lock *req,
			    struct list_head *work_list)
{
	struct list_head *tmp;
	struct ldlm_lock *lock;
	__u64 req_bits = req->l_policy_data.l_inodebits.bits;
	__u64 *try_bits = &req->l_policy_data.l_inodebits.try_bits;
	int compat = 1;

	ENTRY;

	/* There is no sense in lock with no bits set. Also such a lock
	 * would be compatible with any other bit lock.
	 * Meanwhile that can be true if there were just try_bits and all
	 * are failed, so just exit gracefully and let the caller to care.
	 */
	if ((req_bits | *try_bits) == 0)
		RETURN(0);

	list_for_each(tmp, queue) {
		struct list_head *mode_tail;

		lock = list_entry(tmp, struct ldlm_lock, l_res_link);

		/* We stop walking the queue if we hit ourselves so we don't
		 * take conflicting locks enqueued after us into account,
		 * or we'd wait forever. */
		if (req == lock)
			RETURN(compat);

		/* last lock in mode group */
		LASSERT(lock->l_sl_mode.prev != NULL);
		mode_tail = &list_entry(lock->l_sl_mode.prev, struct ldlm_lock,
					l_sl_mode)->l_res_link;

		/* if request lock is not COS_INCOMPAT and COS is disabled,
		 * they are compatible, IOW this request is from a local
		 * transaction on a DNE system. */
		if (lock->l_req_mode == LCK_COS && !ldlm_is_cos_incompat(req) &&
		    !ldlm_is_cos_enabled(req)) {
			/* jump to last lock in mode group */
			tmp = mode_tail;
			continue;
		}

		/* locks' mode are compatible, bits don't matter */
		if (lockmode_compat(lock->l_req_mode, req->l_req_mode)) {
			/* jump to last lock in mode group */
			tmp = mode_tail;
			continue;
		}

		for (;;) {
			struct list_head *head;

			/* Advance loop cursor to last lock in policy group. */
			tmp = &list_entry(lock->l_sl_policy.prev,
					  struct ldlm_lock,
					  l_sl_policy)->l_res_link;

			/* New lock's try_bits are filtered out by ibits
			 * of all locks in both granted and waiting queues.
			 */
			*try_bits &= ~(lock->l_policy_data.l_inodebits.bits |
				lock->l_policy_data.l_inodebits.try_bits);

			if ((req_bits | *try_bits) == 0)
				RETURN(0);

			/* The new lock ibits is more preferable than try_bits
			 * of waiting locks so drop conflicting try_bits in
			 * the waiting queue.
			 * Notice that try_bits of granted locks must be zero.
			 */
			lock->l_policy_data.l_inodebits.try_bits &= ~req_bits;

			/* Locks with overlapping bits conflict. */
			if (lock->l_policy_data.l_inodebits.bits & req_bits) {
				/* COS lock mode has a special compatibility
				 * requirement: it is only compatible with
				 * locks from the same client. */
				if (lock->l_req_mode == LCK_COS &&
				    !ldlm_is_cos_incompat(req) &&
				    ldlm_is_cos_enabled(req) &&
				    lock->l_client_cookie == req->l_client_cookie)
					goto not_conflicting;

				/* Found a conflicting policy group. */
				if (!work_list)
					RETURN(0);

				compat = 0;

				/* Add locks of the policy group to @work_list
				 * as blocking locks for @req */
				if (lock->l_blocking_ast)
					ldlm_add_ast_work_item(lock, req,
							       work_list);
				head = &lock->l_sl_policy;
				list_for_each_entry(lock, head, l_sl_policy)
					if (lock->l_blocking_ast)
						ldlm_add_ast_work_item(lock,
								req, work_list);
			}
not_conflicting:
			if (tmp == mode_tail)
				break;

			tmp = tmp->next;
			lock = list_entry(tmp, struct ldlm_lock, l_res_link);
		} /* Loop over policy groups within one mode group. */
	} /* Loop over mode groups within @queue. */

	RETURN(compat);
}

/**
 * Process a granting attempt for IBITS lock.
 * Must be called with ns lock held
 *
 * This function looks for any conflicts for \a lock in the granted or
 * waiting queues. The lock is granted if no conflicts are found in
 * either queue.
 */
int ldlm_process_inodebits_lock(struct ldlm_lock *lock, __u64 *flags,
				enum ldlm_process_intention intention,
				enum ldlm_error *err,
				struct list_head *work_list)
{
	struct ldlm_resource *res = lock->l_resource;
	struct list_head *grant_work = intention == LDLM_PROCESS_ENQUEUE ?
							NULL : work_list;
	int rc;

	ENTRY;

	LASSERT(!ldlm_is_granted(lock));
	check_res_locked(res);

	if (intention == LDLM_PROCESS_RESCAN) {
		struct list_head *bl_list;

		if (*flags & LDLM_FL_BLOCK_NOWAIT) {
			bl_list = NULL;
			*err = ELDLM_LOCK_WOULDBLOCK;
		} else {
			bl_list = work_list;
			*err = ELDLM_LOCK_ABORTED;
		}

		LASSERT(lock->l_policy_data.l_inodebits.bits != 0);

		/* It is possible that some of granted locks was not canceled
		 * but converted and is kept in granted queue. So there is
		 * a window where lock with 'ast_sent' might become granted
		 * again. Meanwhile a new lock may appear in that window and
		 * conflicts with the converted lock so the following scenario
		 * is possible:
		 *
		 * 1) lock1 conflicts with lock2
		 * 2) bl_ast was sent for lock2
		 * 3) lock3 comes and conflicts with lock2 too
		 * 4) no bl_ast sent because lock2->l_bl_ast_sent is 1
		 * 5) lock2 was converted for lock1 but not for lock3
		 * 6) lock1 granted, lock3 still is waiting for lock2, but
		 *    there will never be another bl_ast for that
		 *
		 * To avoid this scenario the work_list is used below to collect
		 * any blocked locks from granted queue during every reprocess
		 * and bl_ast will be sent if needed.
		 */
		rc = ldlm_inodebits_compat_queue(&res->lr_granted, lock,
						 bl_list);
		if (!rc)
			RETURN(LDLM_ITER_STOP);
		rc = ldlm_inodebits_compat_queue(&res->lr_waiting, lock, NULL);
		if (!rc)
			RETURN(LDLM_ITER_STOP);

		/* grant also try_bits if any */
		if (lock->l_policy_data.l_inodebits.try_bits != 0) {
			lock->l_policy_data.l_inodebits.bits |=
				lock->l_policy_data.l_inodebits.try_bits;
			lock->l_policy_data.l_inodebits.try_bits = 0;
			*flags |= LDLM_FL_LOCK_CHANGED;
		}
		ldlm_resource_unlink_lock(lock);
		ldlm_grant_lock(lock, grant_work);

		*err = ELDLM_OK;
		RETURN(LDLM_ITER_CONTINUE);
	}

	rc = ldlm_inodebits_compat_queue(&res->lr_granted, lock, work_list);
	rc += ldlm_inodebits_compat_queue(&res->lr_waiting, lock, work_list);

	if (rc != 2) {
		/* if there were only bits to try and all are conflicting */
		if ((lock->l_policy_data.l_inodebits.bits |
		     lock->l_policy_data.l_inodebits.try_bits) == 0) {
			*err = ELDLM_LOCK_WOULDBLOCK;
		} else {
			*err = ELDLM_OK;
		}
	} else {
		/* grant also all remaining try_bits */
		if (lock->l_policy_data.l_inodebits.try_bits != 0) {
			lock->l_policy_data.l_inodebits.bits |=
				lock->l_policy_data.l_inodebits.try_bits;
			lock->l_policy_data.l_inodebits.try_bits = 0;
			*flags |= LDLM_FL_LOCK_CHANGED;
		}
		LASSERT(lock->l_policy_data.l_inodebits.bits);
		ldlm_resource_unlink_lock(lock);
		ldlm_grant_lock(lock, grant_work);
		*err = ELDLM_OK;
	}

	RETURN(LDLM_ITER_CONTINUE);
}
#endif /* HAVE_SERVER_SUPPORT */

void ldlm_ibits_policy_wire_to_local(const union ldlm_wire_policy_data *wpolicy,
				     union ldlm_policy_data *lpolicy)
{
	lpolicy->l_inodebits.bits = wpolicy->l_inodebits.bits;
	lpolicy->l_inodebits.try_bits = wpolicy->l_inodebits.try_bits;
}

void ldlm_ibits_policy_local_to_wire(const union ldlm_policy_data *lpolicy,
				     union ldlm_wire_policy_data *wpolicy)
{
	memset(wpolicy, 0, sizeof(*wpolicy));
	wpolicy->l_inodebits.bits = lpolicy->l_inodebits.bits;
	wpolicy->l_inodebits.try_bits = lpolicy->l_inodebits.try_bits;
}

/**
 * Attempt to convert already granted IBITS lock with several bits set to
 * a lock with less bits (downgrade).
 *
 * Such lock conversion is used to keep lock with non-blocking bits instead of
 * cancelling it, introduced for better support of DoM files.
 */
int ldlm_inodebits_drop(struct ldlm_lock *lock, __u64 to_drop)
{
	ENTRY;

	check_res_locked(lock->l_resource);

	/* Just return if there are no conflicting bits */
	if ((lock->l_policy_data.l_inodebits.bits & to_drop) == 0) {
		LDLM_WARN(lock, "try to drop unset bits %#llx/%#llx",
			  lock->l_policy_data.l_inodebits.bits, to_drop);
		/* nothing to do */
		RETURN(0);
	}

	/* remove lock from a skiplist and put in the new place
	 * according with new inodebits */
	ldlm_resource_unlink_lock(lock);
	lock->l_policy_data.l_inodebits.bits &= ~to_drop;
	ldlm_grant_lock_with_skiplist(lock);
	RETURN(0);
}
EXPORT_SYMBOL(ldlm_inodebits_drop);

/* convert single lock */
int ldlm_cli_dropbits(struct ldlm_lock *lock, __u64 drop_bits)
{
	struct lustre_handle lockh;
	__u32 flags = 0;
	int rc;

	ENTRY;

	LASSERT(drop_bits);
	LASSERT(!lock->l_readers && !lock->l_writers);

	LDLM_DEBUG(lock, "client lock convert START");

	ldlm_lock2handle(lock, &lockh);
	lock_res_and_lock(lock);
	/* check if all bits are blocked */
	if (!(lock->l_policy_data.l_inodebits.bits & ~drop_bits)) {
		unlock_res_and_lock(lock);
		/* return error to continue with cancel */
		GOTO(exit, rc = -EINVAL);
	}

	/* check if no common bits, consider this as successful convert */
	if (!(lock->l_policy_data.l_inodebits.bits & drop_bits)) {
		unlock_res_and_lock(lock);
		GOTO(exit, rc = 0);
	}

	/* check if there is race with cancel */
	if (ldlm_is_canceling(lock) || ldlm_is_cancel(lock)) {
		unlock_res_and_lock(lock);
		GOTO(exit, rc = -EINVAL);
	}

	/* clear cbpending flag early, it is safe to match lock right after
	 * client convert because it is downgrade always.
	 */
	ldlm_clear_cbpending(lock);
	ldlm_clear_bl_ast(lock);

	/* If lock is being converted already, check drop bits first */
	if (ldlm_is_converting(lock)) {
		/* raced lock convert, lock inodebits are remaining bits
		 * so check if they are conflicting with new convert or not.
		 */
		if (!(lock->l_policy_data.l_inodebits.bits & drop_bits)) {
			unlock_res_and_lock(lock);
			GOTO(exit, rc = 0);
		}
		/* Otherwise drop new conflicting bits in new convert */
	}
	ldlm_set_converting(lock);
	/* from all bits of blocking lock leave only conflicting */
	drop_bits &= lock->l_policy_data.l_inodebits.bits;
	/* save them in cancel_bits, so l_blocking_ast will know
	 * which bits from the current lock were dropped. */
	lock->l_policy_data.l_inodebits.cancel_bits = drop_bits;
	/* Finally clear these bits in lock ibits */
	ldlm_inodebits_drop(lock, drop_bits);
	unlock_res_and_lock(lock);
	/* Finally call cancel callback for remaining bits only.
	 * It is important to have converting flag during that
	 * so blocking_ast callback can distinguish convert from
	 * cancels.
	 */
	if (lock->l_blocking_ast)
		lock->l_blocking_ast(lock, NULL, lock->l_ast_data,
				     LDLM_CB_CANCELING);

	/* now notify server about convert */
	rc = ldlm_cli_convert(lock, &flags);
	if (rc) {
		lock_res_and_lock(lock);
		if (ldlm_is_converting(lock)) {
			ldlm_clear_converting(lock);
			ldlm_set_cbpending(lock);
			ldlm_set_bl_ast(lock);
		}
		unlock_res_and_lock(lock);
		GOTO(exit, rc);
	}
	EXIT;
exit:
	LDLM_DEBUG(lock, "client lock convert END");
	return rc;
}


int ldlm_inodebits_alloc_lock(struct ldlm_lock *lock)
{
	if (ldlm_is_ns_srv(lock)) {
		int i;

		OBD_SLAB_ALLOC_PTR(lock->l_ibits_node, ldlm_inodebits_slab);
		if (lock->l_ibits_node == NULL)
			return -ENOMEM;
		for (i = 0; i < MDS_INODELOCK_NUMBITS; i++)
			INIT_LIST_HEAD(&lock->l_ibits_node->lin_link[i]);
		lock->l_ibits_node->lock = lock;
	} else {
		lock->l_ibits_node = NULL;
	}
	return 0;
}

void ldlm_inodebits_add_lock(struct ldlm_resource *res, struct list_head *head,
			     struct ldlm_lock *lock)
{
	int i;

	if (!ldlm_is_ns_srv(lock))
		return;

	if (head == &res->lr_waiting) {
		for (i = 0; i < MDS_INODELOCK_NUMBITS; i++) {
			if (lock->l_policy_data.l_inodebits.bits & (1 << i))
				list_add_tail(&lock->l_ibits_node->lin_link[i],
					&res->lr_ibits_queues->liq_waiting[i]);
		}
	} else if (head == &res->lr_granted && lock->l_ibits_node != NULL) {
		for (i = 0; i < MDS_INODELOCK_NUMBITS; i++)
			LASSERT(list_empty(&lock->l_ibits_node->lin_link[i]));
		OBD_SLAB_FREE_PTR(lock->l_ibits_node, ldlm_inodebits_slab);
		lock->l_ibits_node = NULL;
	}
}

void ldlm_inodebits_unlink_lock(struct ldlm_lock *lock)
{
	int i;

	ldlm_unlink_lock_skiplist(lock);
	if (!ldlm_is_ns_srv(lock))
		return;

	for (i = 0; i < MDS_INODELOCK_NUMBITS; i++)
		list_del_init(&lock->l_ibits_node->lin_link[i]);
}