/* AFS vnode management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "internal.h"

#if 0
static noinline bool dump_tree_aux(struct rb_node *node, struct rb_node *parent,
				   int depth, char lr)
{
	struct afs_vnode *vnode;
	bool bad = false;

	if (!node)
		return false;

	if (node->rb_left)
		bad = dump_tree_aux(node->rb_left, node, depth + 2, '/');

	vnode = rb_entry(node, struct afs_vnode, cb_promise);
	kdebug("%c %*.*s%c%p {%d}",
	       rb_is_red(node) ? 'R' : 'B',
	       depth, depth, "", lr,
	       vnode, vnode->cb_expires_at);
	if (rb_parent(node) != parent) {
		printk("BAD: %p != %p\n", rb_parent(node), parent);
		bad = true;
	}

	if (node->rb_right)
		bad |= dump_tree_aux(node->rb_right, node, depth + 2, '\\');

	return bad;
}

static noinline void dump_tree(const char *name, struct afs_server *server)
{
	kenter("%s", name);
	if (dump_tree_aux(server->cb_promises.rb_node, NULL, 0, '-'))
		BUG();
}
#endif

/*
 * insert a vnode into the backing server's vnode tree
 */
static void afs_install_vnode(struct afs_vnode *vnode,
			      struct afs_server *server)
{
	struct afs_server *old_server = vnode->server;
	struct afs_vnode *xvnode;
	struct rb_node *parent, **p;

	_enter("%p,%p", vnode, server);

	if (old_server) {
		spin_lock(&old_server->fs_lock);
		rb_erase(&vnode->server_rb, &old_server->fs_vnodes);
		spin_unlock(&old_server->fs_lock);
	}

	afs_get_server(server);
	vnode->server = server;
	afs_put_server(old_server);

	/* insert into the server's vnode tree in FID order */
	spin_lock(&server->fs_lock);

	parent = NULL;
	p = &server->fs_vnodes.rb_node;
	while (*p) {
		parent = *p;
		xvnode = rb_entry(parent, struct afs_vnode, server_rb);
		if (vnode->fid.vid < xvnode->fid.vid)
			p = &(*p)->rb_left;
		else if (vnode->fid.vid > xvnode->fid.vid)
			p = &(*p)->rb_right;
		else if (vnode->fid.vnode < xvnode->fid.vnode)
			p = &(*p)->rb_left;
		else if (vnode->fid.vnode > xvnode->fid.vnode)
			p = &(*p)->rb_right;
		else if (vnode->fid.unique < xvnode->fid.unique)
			p = &(*p)->rb_left;
		else if (vnode->fid.unique > xvnode->fid.unique)
			p = &(*p)->rb_right;
		else
			BUG(); /* can't happen unless afs_iget() malfunctions */
	}

	rb_link_node(&vnode->server_rb, parent, p);
	rb_insert_color(&vnode->server_rb, &server->fs_vnodes);

	spin_unlock(&server->fs_lock);
	_leave("");
}

/*
 * insert a vnode into the promising server's update/expiration tree
 * - caller must hold vnode->lock
 */
static void afs_vnode_note_promise(struct afs_vnode *vnode,
				   struct afs_server *server)
{
	struct afs_server *old_server;
	struct afs_vnode *xvnode;
	struct rb_node *parent, **p;

	_enter("%p,%p", vnode, server);

	ASSERT(server != NULL);

	old_server = vnode->server;
	if (vnode->cb_promised) {
		if (server == old_server &&
		    vnode->cb_expires == vnode->cb_expires_at) {
			_leave(" [no change]");
			return;
		}

		spin_lock(&old_server->cb_lock);
		if (vnode->cb_promised) {
			_debug("delete");
			rb_erase(&vnode->cb_promise, &old_server->cb_promises);
			vnode->cb_promised = false;
		}
		spin_unlock(&old_server->cb_lock);
	}

	if (vnode->server != server)
		afs_install_vnode(vnode, server);

	vnode->cb_expires_at = vnode->cb_expires;
	_debug("PROMISE on %p {%lu}",
	       vnode, (unsigned long) vnode->cb_expires_at);

	/* abuse an RB-tree to hold the expiration order (we may have multiple
	 * items with the same expiration time) */
	spin_lock(&server->cb_lock);

	parent = NULL;
	p = &server->cb_promises.rb_node;
	while (*p) {
		parent = *p;
		xvnode = rb_entry(parent, struct afs_vnode, cb_promise);
		if (vnode->cb_expires_at < xvnode->cb_expires_at)
			p = &(*p)->rb_left;
		else
			p = &(*p)->rb_right;
	}

	rb_link_node(&vnode->cb_promise, parent, p);
	rb_insert_color(&vnode->cb_promise, &server->cb_promises);
	vnode->cb_promised = true;

	spin_unlock(&server->cb_lock);
	_leave("");
}

/*
 * handle remote file deletion by discarding the callback promise
 */
static void afs_vnode_deleted_remotely(struct afs_vnode *vnode)
{
	struct afs_server *server;

	set_bit(AFS_VNODE_DELETED, &vnode->flags);

	server = vnode->server;
	if (vnode->cb_promised) {
		spin_lock(&server->cb_lock);
		if (vnode->cb_promised) {
			rb_erase(&vnode->cb_promise, &server->cb_promises);
			vnode->cb_promised = false;
		}
		spin_unlock(&server->cb_lock);
	}

	afs_put_server(server);
}

/*
 * finish off updating the recorded status of a file
 * - starts callback expiry timer
 * - adds to server's callback list
 */
static void afs_vnode_finalise_status_update(struct afs_vnode *vnode,
					     struct afs_server *server,
					     int ret)
{
	struct afs_server *oldserver = NULL;

	_enter("%p,%p,%d", vnode, server, ret);

	spin_lock(&vnode->lock);

	clear_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);

	switch (ret) {
	case 0:
		afs_vnode_note_promise(vnode, server);
		break;
	case -ENOENT:
		/* the file was deleted on the server */
		_debug("got NOENT from server - marking file deleted");
		afs_vnode_deleted_remotely(vnode);
		break;
	default:
		break;
	}

	vnode->update_cnt--;

	spin_unlock(&vnode->lock);

	wake_up_all(&vnode->update_waitq);

	afs_put_server(oldserver);

	_leave("");
}

/*
 * fetch file status from the volume
 * - don't issue a fetch if:
 *   - the changed bit is not set and there's a valid callback
 *   - there are any outstanding ops that will fetch the status
 * - TODO implement local caching
 */
int afs_vnode_fetch_status(struct afs_vnode *vnode,
			   struct afs_vnode *auth_vnode, struct key *key)
{
	struct afs_server *server;
	unsigned long acl_order;
	int ret;

	DECLARE_WAITQUEUE(myself, current);

	_enter("%s,{%u,%u,%u}",
	       vnode->volume->vlocation->vldb.name,
	       vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);

	if (!test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags) &&
	    vnode->cb_promised) {
		_leave(" [unchanged]");
		return 0;
	}

	if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
		_leave(" [deleted]");
		return -ENOENT;
	}

	acl_order = 0;
	if (auth_vnode)
		acl_order = auth_vnode->acl_order;

	spin_lock(&vnode->lock);

	if (!test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags) &&
	    vnode->cb_promised) {
		spin_unlock(&vnode->lock);
		_leave(" [unchanged]");
		return 0;
	}

	if (vnode->update_cnt > 0) {
		/* someone else started a fetch */
		set_current_state(TASK_UNINTERRUPTIBLE);
		ASSERT(myself.func != NULL);
		add_wait_queue(&vnode->update_waitq, &myself);

		/* wait for the status to be updated */
		for (;;) {
			if (!test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags))
				break;
			if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
				break;

			/* check to see if it got updated and invalidated all
			 * before we saw it */
			if (vnode->update_cnt == 0) {
				remove_wait_queue(&vnode->update_waitq,
						  &myself);
				set_current_state(TASK_RUNNING);
				goto get_anyway;
			}

			spin_unlock(&vnode->lock);

			schedule();
			set_current_state(TASK_UNINTERRUPTIBLE);

			spin_lock(&vnode->lock);
		}

		remove_wait_queue(&vnode->update_waitq, &myself);
		spin_unlock(&vnode->lock);
		set_current_state(TASK_RUNNING);

		return test_bit(AFS_VNODE_DELETED, &vnode->flags) ?
			-ENOENT : 0;
	}

get_anyway:
	/* okay... we're going to have to initiate the op */
	vnode->update_cnt++;

	spin_unlock(&vnode->lock);

	/* merge AFS status fetches and clear outstanding callback on this
	 * vnode */
	do {
		/* pick a server to query */
		server = afs_volume_pick_fileserver(vnode);
		if (IS_ERR(server))
			return PTR_ERR(server);

		_debug("USING SERVER: %p{%08x}",
		       server, ntohl(server->addr.s_addr));

		ret = afs_fs_fetch_file_status(server, key, vnode, NULL,
					       &afs_sync_call);

	} while (!afs_volume_release_fileserver(vnode, server, ret));

	/* adjust the flags */
	if (ret == 0 && auth_vnode)
		afs_cache_permit(vnode, key, acl_order);
	afs_vnode_finalise_status_update(vnode, server, ret);

	_leave(" = %d", ret);
	return ret;
}

/*
 * fetch file data from the volume
 * - TODO implement caching and server failover
 */
int afs_vnode_fetch_data(struct afs_vnode *vnode, struct key *key,
			 off_t offset, size_t length, struct page *page)
{
	struct afs_server *server;
	int ret;

	_enter("%s{%u,%u,%u},%x,,,",
	       vnode->volume->vlocation->vldb.name,
	       vnode->fid.vid,
	       vnode->fid.vnode,
	       vnode->fid.unique,
	       key_serial(key));

	/* this op will fetch the status */
	spin_lock(&vnode->lock);
	vnode->update_cnt++;
	spin_unlock(&vnode->lock);

	/* merge in AFS status fetches and clear outstanding callback on this
	 * vnode */
	do {
		/* pick a server to query */
		server = afs_volume_pick_fileserver(vnode);
		if (IS_ERR(server))
			return PTR_ERR(server);

		_debug("USING SERVER: %08x\n", ntohl(server->addr.s_addr));

		ret = afs_fs_fetch_data(server, key, vnode, offset, length,
					page, NULL, &afs_sync_call);

	} while (!afs_volume_release_fileserver(vnode, server, ret));

	/* adjust the flags */
	afs_vnode_finalise_status_update(vnode, server, ret);

	_leave(" = %d", ret);
	return ret;
}