/*
 * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
 *
 * This software may be freely redistributed under the terms of the
 * GNU General Public License.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Authors: David Woodhouse <dwmw2@infradead.org>
 *          David Howells <dhowells@redhat.com>
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/circ_buf.h>
#include <linux/sched.h>
#include "internal.h"

/*
 * Create volume and callback interests on a server.
 */
static struct afs_cb_interest *afs_create_interest(struct afs_server *server,
						   struct afs_vnode *vnode)
{
	struct afs_vol_interest *new_vi, *vi;
	struct afs_cb_interest *new;
	struct hlist_node **pp;

	new_vi = kzalloc(sizeof(struct afs_vol_interest), GFP_KERNEL);
	if (!new_vi)
		return NULL;

	new = kzalloc(sizeof(struct afs_cb_interest), GFP_KERNEL);
	if (!new) {
		kfree(new_vi);
		return NULL;
	}

	new_vi->usage = 1;
	new_vi->vid = vnode->volume->vid;
	INIT_HLIST_NODE(&new_vi->srv_link);
	INIT_HLIST_HEAD(&new_vi->cb_interests);

	refcount_set(&new->usage, 1);
	new->sb = vnode->vfs_inode.i_sb;
	new->vid = vnode->volume->vid;
	new->server = afs_get_server(server, afs_server_trace_get_new_cbi);
	INIT_HLIST_NODE(&new->cb_vlink);

	write_lock(&server->cb_break_lock);

	for (pp = &server->cb_volumes.first; *pp; pp = &(*pp)->next) {
		vi = hlist_entry(*pp, struct afs_vol_interest, srv_link);
		if (vi->vid < new_vi->vid)
			continue;
		if (vi->vid > new_vi->vid)
			break;
		vi->usage++;
		goto found_vi;
	}

	new_vi->srv_link.pprev = pp;
	new_vi->srv_link.next = *pp;
	if (*pp)
		(*pp)->pprev = &new_vi->srv_link.next;
	*pp = &new_vi->srv_link;
	vi = new_vi;
	new_vi = NULL;
found_vi:

	new->vol_interest = vi;
	hlist_add_head(&new->cb_vlink, &vi->cb_interests);

	write_unlock(&server->cb_break_lock);
	kfree(new_vi);
	return new;
}

/*
 * Set up an interest-in-callbacks record for a volume on a server and
 * register it with the server.
 * - Called with vnode->io_lock held.
 */
int afs_register_server_cb_interest(struct afs_vnode *vnode,
				    struct afs_server_list *slist,
				    unsigned int index)
{
	struct afs_server_entry *entry = &slist->servers[index];
	struct afs_cb_interest *cbi, *vcbi, *new, *old;
	struct afs_server *server = entry->server;

again:
	vcbi = rcu_dereference_protected(vnode->cb_interest,
					 lockdep_is_held(&vnode->io_lock));
	if (vcbi && likely(vcbi == entry->cb_interest))
		return 0;

	read_lock(&slist->lock);
	cbi = afs_get_cb_interest(entry->cb_interest);
	read_unlock(&slist->lock);

	if (vcbi) {
		if (vcbi == cbi) {
			afs_put_cb_interest(afs_v2net(vnode), cbi);
			return 0;
		}

		/* Use a new interest in the server list for the same server
		 * rather than an old one that's still attached to a vnode.
		 */
		if (cbi && vcbi->server == cbi->server) {
			write_seqlock(&vnode->cb_lock);
			old = rcu_dereference_protected(vnode->cb_interest,
							lockdep_is_held(&vnode->cb_lock.lock));
			rcu_assign_pointer(vnode->cb_interest, cbi);
			write_sequnlock(&vnode->cb_lock);
			afs_put_cb_interest(afs_v2net(vnode), old);
			return 0;
		}

		/* Re-use the one attached to the vnode. */
		if (!cbi && vcbi->server == server) {
			write_lock(&slist->lock);
			if (entry->cb_interest) {
				write_unlock(&slist->lock);
				afs_put_cb_interest(afs_v2net(vnode), cbi);
				goto again;
			}

			entry->cb_interest = cbi;
			write_unlock(&slist->lock);
			return 0;
		}
	}

	if (!cbi) {
		new = afs_create_interest(server, vnode);
		if (!new)
			return -ENOMEM;

		write_lock(&slist->lock);
		if (!entry->cb_interest) {
			entry->cb_interest = afs_get_cb_interest(new);
			cbi = new;
			new = NULL;
		} else {
			cbi = afs_get_cb_interest(entry->cb_interest);
		}
		write_unlock(&slist->lock);
		afs_put_cb_interest(afs_v2net(vnode), new);
	}

	ASSERT(cbi);

	/* Change the server the vnode is using.  This entails scrubbing any
	 * interest the vnode had in the previous server it was using.
	 */
	write_seqlock(&vnode->cb_lock);

	old = rcu_dereference_protected(vnode->cb_interest,
					lockdep_is_held(&vnode->cb_lock.lock));
	rcu_assign_pointer(vnode->cb_interest, cbi);
	vnode->cb_s_break = cbi->server->cb_s_break;
	vnode->cb_v_break = vnode->volume->cb_v_break;
	clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);

	write_sequnlock(&vnode->cb_lock);
	afs_put_cb_interest(afs_v2net(vnode), old);
	return 0;
}

/*
 * Remove an interest on a server.
 */
void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
{
	struct afs_vol_interest *vi;

	if (cbi && refcount_dec_and_test(&cbi->usage)) {
		if (!hlist_unhashed(&cbi->cb_vlink)) {
			write_lock(&cbi->server->cb_break_lock);

			hlist_del_init(&cbi->cb_vlink);
			vi = cbi->vol_interest;
			cbi->vol_interest = NULL;
			if (--vi->usage == 0)
				hlist_del(&vi->srv_link);
			else
				vi = NULL;

			write_unlock(&cbi->server->cb_break_lock);
			if (vi)
				kfree_rcu(vi, rcu);
			afs_put_server(net, cbi->server, afs_server_trace_put_cbi);
		}
		kfree_rcu(cbi, rcu);
	}
}

/*
 * allow the fileserver to request callback state (re-)initialisation
 */
void afs_init_callback_state(struct afs_server *server)
{
	server->cb_s_break++;
}

/*
 * actually break a callback
 */
void __afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
{
	_enter("");

	clear_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
	if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
		vnode->cb_break++;
		afs_clear_permits(vnode);

		if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
			afs_lock_may_be_available(vnode);

		trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, true);
	} else {
		trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, false);
	}
}

void afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
{
	write_seqlock(&vnode->cb_lock);
	__afs_break_callback(vnode, reason);
	write_sequnlock(&vnode->cb_lock);
}

/*
 * allow the fileserver to explicitly break one callback
 * - happens when
 *   - the backing file is changed
 *   - a lock is released
 */
static void afs_break_one_callback(struct afs_server *server,
				   struct afs_fid *fid)
{
	struct afs_vol_interest *vi;
	struct afs_cb_interest *cbi;
	struct afs_iget_data data;
	struct afs_vnode *vnode;
	struct inode *inode;

	read_lock(&server->cb_break_lock);
	hlist_for_each_entry(vi, &server->cb_volumes, srv_link) {
		if (vi->vid < fid->vid)
			continue;
		if (vi->vid > fid->vid) {
			vi = NULL;
			break;
		}
		//atomic_inc(&vi->usage);
		break;
	}

	/* TODO: Find all matching volumes if we couldn't match the server and
	 * break them anyway.
	 */
	if (!vi)
		goto out;

	/* Step through all interested superblocks.  There may be more than one
	 * because of cell aliasing.
	 */
	hlist_for_each_entry(cbi, &vi->cb_interests, cb_vlink) {
		if (fid->vnode == 0 && fid->unique == 0) {
			/* The callback break applies to an entire volume. */
			struct afs_super_info *as = AFS_FS_S(cbi->sb);
			struct afs_volume *volume = as->volume;

			write_lock(&volume->cb_v_break_lock);
			volume->cb_v_break++;
			trace_afs_cb_break(fid, volume->cb_v_break,
					   afs_cb_break_for_volume_callback, false);
			write_unlock(&volume->cb_v_break_lock);
		} else {
			data.volume = NULL;
			data.fid = *fid;
			inode = ilookup5_nowait(cbi->sb, fid->vnode,
						afs_iget5_test, &data);
			if (inode) {
				vnode = AFS_FS_I(inode);
				afs_break_callback(vnode, afs_cb_break_for_callback);
				iput(inode);
			} else {
				trace_afs_cb_miss(fid, afs_cb_break_for_callback);
			}
		}
	}

out:
	read_unlock(&server->cb_break_lock);
}

/*
 * allow the fileserver to break callback promises
 */
void afs_break_callbacks(struct afs_server *server, size_t count,
			 struct afs_callback_break *callbacks)
{
	_enter("%p,%zu,", server, count);

	ASSERT(server != NULL);
	ASSERTCMP(count, <=, AFSCBMAX);

	/* TODO: Sort the callback break list by volume ID */

	for (; count > 0; callbacks++, count--) {
		_debug("- Fid { vl=%08llx n=%llu u=%u }",
		       callbacks->fid.vid,
		       callbacks->fid.vnode,
		       callbacks->fid.unique);
		afs_break_one_callback(server, &callbacks->fid);
	}

	_leave("");
	return;
}

/*
 * Clear the callback interests in a server list.
 */
void afs_clear_callback_interests(struct afs_net *net, struct afs_server_list *slist)
{
	int i;

	for (i = 0; i < slist->nr_servers; i++) {
		afs_put_cb_interest(net, slist->servers[i].cb_interest);
		slist->servers[i].cb_interest = NULL;
	}
}