[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / fs / afs / cell.c

/* AFS cell and server record management
 *
 * Copyright (C) 2002 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/module.h>
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

DECLARE_RWSEM(afs_proc_cells_sem);
LIST_HEAD(afs_proc_cells);

static LIST_HEAD(afs_cells);
static DEFINE_RWLOCK(afs_cells_lock);
static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
static struct afs_cell *afs_cell_root;

/*
 * allocate a cell record and fill in its name, VL server address list and
 * allocate an anonymous key
 */
static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
				       char *vllist)
{
	struct afs_cell *cell;
	struct key *key;
	char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
	char  *dvllist = NULL, *_vllist = NULL;
	char  delimiter = ':';
	int ret;

	_enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);

	BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */

	if (namelen > AFS_MAXCELLNAME) {
		_leave(" = -ENAMETOOLONG");
		return ERR_PTR(-ENAMETOOLONG);
	}

	/* allocate and initialise a cell record */
	cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
	if (!cell) {
		_leave(" = -ENOMEM");
		return ERR_PTR(-ENOMEM);
	}

	memcpy(cell->name, name, namelen);
	cell->name[namelen] = 0;

	atomic_set(&cell->usage, 1);
	INIT_LIST_HEAD(&cell->link);
	rwlock_init(&cell->servers_lock);
	INIT_LIST_HEAD(&cell->servers);
	init_rwsem(&cell->vl_sem);
	INIT_LIST_HEAD(&cell->vl_list);
	spin_lock_init(&cell->vl_lock);

	/* if the ip address is invalid, try dns query */
	if (!vllist || strlen(vllist) < 7) {
		ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
		if (ret < 0) {
			if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
				/* translate these errors into something
				 * userspace might understand */
				ret = -EDESTADDRREQ;
			_leave(" = %d", ret);
			return ERR_PTR(ret);
		}
		_vllist = dvllist;

		/* change the delimiter for user-space reply */
		delimiter = ',';

	} else {
		_vllist = vllist;
	}

	/* fill in the VL server list from the rest of the string */
	do {
		unsigned a, b, c, d;

		next = strchr(_vllist, delimiter);
		if (next)
			*next++ = 0;

		if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
			goto bad_address;

		if (a > 255 || b > 255 || c > 255 || d > 255)
			goto bad_address;

		cell->vl_addrs[cell->vl_naddrs++].s_addr =
			htonl((a << 24) | (b << 16) | (c << 8) | d);

	} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));

	/* create a key to represent an anonymous user */
	memcpy(keyname, "afs@", 4);
	dp = keyname + 4;
	cp = cell->name;
	do {
		*dp++ = toupper(*cp);
	} while (*cp++);

	key = rxrpc_get_null_key(keyname);
	if (IS_ERR(key)) {
		_debug("no key");
		ret = PTR_ERR(key);
		goto error;
	}
	cell->anonymous_key = key;

	_debug("anon key %p{%x}",
	       cell->anonymous_key, key_serial(cell->anonymous_key));

	_leave(" = %p", cell);
	return cell;

bad_address:
	printk(KERN_ERR "kAFS: bad VL server IP address\n");
	ret = -EINVAL;
error:
	key_put(cell->anonymous_key);
	kfree(dvllist);
	kfree(cell);
	_leave(" = %d", ret);
	return ERR_PTR(ret);
}

/*
 * afs_cell_crate() - create a cell record
 * @name:	is the name of the cell.
 * @namsesz:	is the strlen of the cell name.
 * @vllist:	is a colon separated list of IP addresses in "a.b.c.d" format.
 * @retref:	is T to return the cell reference when the cell exists.
 */
struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
				 char *vllist, bool retref)
{
	struct afs_cell *cell;
	int ret;

	_enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);

	down_write(&afs_cells_sem);
	read_lock(&afs_cells_lock);
	list_for_each_entry(cell, &afs_cells, link) {
		if (strncasecmp(cell->name, name, namesz) == 0)
			goto duplicate_name;
	}
	read_unlock(&afs_cells_lock);

	cell = afs_cell_alloc(name, namesz, vllist);
	if (IS_ERR(cell)) {
		_leave(" = %ld", PTR_ERR(cell));
		up_write(&afs_cells_sem);
		return cell;
	}

	/* add a proc directory for this cell */
	ret = afs_proc_cell_setup(cell);
	if (ret < 0)
		goto error;

#ifdef CONFIG_AFS_FSCACHE
	/* put it up for caching (this never returns an error) */
	cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
					     &afs_cell_cache_index_def,
					     cell, true);
#endif

	/* add to the cell lists */
	write_lock(&afs_cells_lock);
	list_add_tail(&cell->link, &afs_cells);
	write_unlock(&afs_cells_lock);

	down_write(&afs_proc_cells_sem);
	list_add_tail(&cell->proc_link, &afs_proc_cells);
	up_write(&afs_proc_cells_sem);
	up_write(&afs_cells_sem);

	_leave(" = %p", cell);
	return cell;

error:
	up_write(&afs_cells_sem);
	key_put(cell->anonymous_key);
	kfree(cell);
	_leave(" = %d", ret);
	return ERR_PTR(ret);

duplicate_name:
	if (retref && !IS_ERR(cell))
		afs_get_cell(cell);

	read_unlock(&afs_cells_lock);
	up_write(&afs_cells_sem);

	if (retref) {
		_leave(" = %p", cell);
		return cell;
	}

	_leave(" = -EEXIST");
	return ERR_PTR(-EEXIST);
}

/*
 * set the root cell information
 * - can be called with a module parameter string
 * - can be called from a write to /proc/fs/afs/rootcell
 */
int afs_cell_init(char *rootcell)
{
	struct afs_cell *old_root, *new_root;
	char *cp;

	_enter("");

	if (!rootcell) {
		/* module is loaded with no parameters, or built statically.
		 * - in the future we might initialize cell DB here.
		 */
		_leave(" = 0 [no root]");
		return 0;
	}

	cp = strchr(rootcell, ':');
	if (!cp)
		_debug("kAFS: no VL server IP addresses specified");
	else
		*cp++ = 0;

	/* allocate a cell record for the root cell */
	new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
	if (IS_ERR(new_root)) {
		_leave(" = %ld", PTR_ERR(new_root));
		return PTR_ERR(new_root);
	}

	/* install the new cell */
	write_lock(&afs_cells_lock);
	old_root = afs_cell_root;
	afs_cell_root = new_root;
	write_unlock(&afs_cells_lock);
	afs_put_cell(old_root);

	_leave(" = 0");
	return 0;
}

/*
 * lookup a cell record
 */
struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
				 bool dns_cell)
{
	struct afs_cell *cell;

	_enter("\"%*.*s\",", namesz, namesz, name ?: "");

	down_read(&afs_cells_sem);
	read_lock(&afs_cells_lock);

	if (name) {
		/* if the cell was named, look for it in the cell record list */
		list_for_each_entry(cell, &afs_cells, link) {
			if (strncmp(cell->name, name, namesz) == 0) {
				afs_get_cell(cell);
				goto found;
			}
		}
		cell = ERR_PTR(-ENOENT);
		if (dns_cell)
			goto create_cell;
	found:
		;
	} else {
		cell = afs_cell_root;
		if (!cell) {
			/* this should not happen unless user tries to mount
			 * when root cell is not set. Return an impossibly
			 * bizarre errno to alert the user. Things like
			 * ENOENT might be "more appropriate" but they happen
			 * for other reasons.
			 */
			cell = ERR_PTR(-EDESTADDRREQ);
		} else {
			afs_get_cell(cell);
		}

	}

	read_unlock(&afs_cells_lock);
	up_read(&afs_cells_sem);
	_leave(" = %p", cell);
	return cell;

create_cell:
	read_unlock(&afs_cells_lock);
	up_read(&afs_cells_sem);

	cell = afs_cell_create(name, namesz, NULL, true);

	_leave(" = %p", cell);
	return cell;
}

#if 0
/*
 * try and get a cell record
 */
struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
{
	write_lock(&afs_cells_lock);

	if (cell && !list_empty(&cell->link))
		afs_get_cell(cell);
	else
		cell = NULL;

	write_unlock(&afs_cells_lock);
	return cell;
}
#endif  /*  0  */

/*
 * destroy a cell record
 */
void afs_put_cell(struct afs_cell *cell)
{
	if (!cell)
		return;

	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

	ASSERTCMP(atomic_read(&cell->usage), >, 0);

	/* to prevent a race, the decrement and the dequeue must be effectively
	 * atomic */
	write_lock(&afs_cells_lock);

	if (likely(!atomic_dec_and_test(&cell->usage))) {
		write_unlock(&afs_cells_lock);
		_leave("");
		return;
	}

	ASSERT(list_empty(&cell->servers));
	ASSERT(list_empty(&cell->vl_list));

	write_unlock(&afs_cells_lock);

	wake_up(&afs_cells_freeable_wq);

	_leave(" [unused]");
}

/*
 * destroy a cell record
 * - must be called with the afs_cells_sem write-locked
 * - cell->link should have been broken by the caller
 */
static void afs_cell_destroy(struct afs_cell *cell)
{
	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

	ASSERTCMP(atomic_read(&cell->usage), >=, 0);
	ASSERT(list_empty(&cell->link));

	/* wait for everyone to stop using the cell */
	if (atomic_read(&cell->usage) > 0) {
		DECLARE_WAITQUEUE(myself, current);

		_debug("wait for cell %s", cell->name);
		set_current_state(TASK_UNINTERRUPTIBLE);
		add_wait_queue(&afs_cells_freeable_wq, &myself);

		while (atomic_read(&cell->usage) > 0) {
			schedule();
			set_current_state(TASK_UNINTERRUPTIBLE);
		}

		remove_wait_queue(&afs_cells_freeable_wq, &myself);
		set_current_state(TASK_RUNNING);
	}

	_debug("cell dead");
	ASSERTCMP(atomic_read(&cell->usage), ==, 0);
	ASSERT(list_empty(&cell->servers));
	ASSERT(list_empty(&cell->vl_list));

	afs_proc_cell_remove(cell);

	down_write(&afs_proc_cells_sem);
	list_del_init(&cell->proc_link);
	up_write(&afs_proc_cells_sem);

#ifdef CONFIG_AFS_FSCACHE
	fscache_relinquish_cookie(cell->cache, 0);
#endif
	key_put(cell->anonymous_key);
	kfree(cell);

	_leave(" [destroyed]");
}

/*
 * purge in-memory cell database on module unload or afs_init() failure
 * - the timeout daemon is stopped before calling this
 */
void afs_cell_purge(void)
{
	struct afs_cell *cell;

	_enter("");

	afs_put_cell(afs_cell_root);

	down_write(&afs_cells_sem);

	while (!list_empty(&afs_cells)) {
		cell = NULL;

		/* remove the next cell from the front of the list */
		write_lock(&afs_cells_lock);

		if (!list_empty(&afs_cells)) {
			cell = list_entry(afs_cells.next,
					  struct afs_cell, link);
			list_del_init(&cell->link);
		}

		write_unlock(&afs_cells_lock);

		if (cell) {
			_debug("PURGING CELL %s (%d)",
			       cell->name, atomic_read(&cell->usage));

			/* now the cell should be left with no references */
			afs_cell_destroy(cell);
		}
	}

	up_write(&afs_cells_sem);
	_leave("");
}
Commit	Line	Data
	1	/* AFS cell and server record management
	2	*
	3	* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#include <linux/module.h>
	13	#include <linux/slab.h>
	14	#include <linux/key.h>
	15	#include <linux/ctype.h>
	16	#include <linux/dns_resolver.h>
	17	#include <linux/sched.h>
	18	#include <keys/rxrpc-type.h>
	19	#include "internal.h"
	20
	21	DECLARE_RWSEM(afs_proc_cells_sem);
	22	LIST_HEAD(afs_proc_cells);
	23
	24	static LIST_HEAD(afs_cells);
	25	static DEFINE_RWLOCK(afs_cells_lock);
	26	static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
	27	static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
	28	static struct afs_cell *afs_cell_root;
	29
	30	/*
	31	* allocate a cell record and fill in its name, VL server address list and
	32	* allocate an anonymous key
	33	*/
	34	static struct afs_cell afs_cell_alloc(const char name, unsigned namelen,
	35	char *vllist)
	36	{
	37	struct afs_cell *cell;
	38	struct key *key;
	39	char keyname[4 + AFS_MAXCELLNAME + 1], cp, dp, *next;
	40	char dvllist = NULL, _vllist = NULL;
	41	char delimiter = ':';
	42	int ret;
	43
	44	_enter("%.s,%s", namelen, namelen, name ?: "", vllist);
	45
	46	BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
	47
	48	if (namelen > AFS_MAXCELLNAME) {
	49	_leave(" = -ENAMETOOLONG");
	50	return ERR_PTR(-ENAMETOOLONG);
	51	}
	52
	53	/* allocate and initialise a cell record */
	54	cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
	55	if (!cell) {
	56	_leave(" = -ENOMEM");
	57	return ERR_PTR(-ENOMEM);
	58	}
	59
	60	memcpy(cell->name, name, namelen);
	61	cell->name[namelen] = 0;
	62
	63	atomic_set(&cell->usage, 1);
	64	INIT_LIST_HEAD(&cell->link);
	65	rwlock_init(&cell->servers_lock);
	66	INIT_LIST_HEAD(&cell->servers);
	67	init_rwsem(&cell->vl_sem);
	68	INIT_LIST_HEAD(&cell->vl_list);
	69	spin_lock_init(&cell->vl_lock);
	70
	71	/* if the ip address is invalid, try dns query */
	72	if (!vllist \|\| strlen(vllist) < 7) {
	73	ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
	74	if (ret < 0) {
	75	if (ret == -ENODATA \|\| ret == -EAGAIN \|\| ret == -ENOKEY)
	76	/* translate these errors into something
	77	* userspace might understand */
	78	ret = -EDESTADDRREQ;
	79	_leave(" = %d", ret);
	80	return ERR_PTR(ret);
	81	}
	82	_vllist = dvllist;
	83
	84	/* change the delimiter for user-space reply */
	85	delimiter = ',';
	86
	87	} else {
	88	_vllist = vllist;
	89	}
	90
	91	/* fill in the VL server list from the rest of the string */
	92	do {
	93	unsigned a, b, c, d;
	94
	95	next = strchr(_vllist, delimiter);
	96	if (next)
	97	*next++ = 0;
	98
	99	if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
	100	goto bad_address;
	101
	102	if (a > 255 \|\| b > 255 \|\| c > 255 \|\| d > 255)
	103	goto bad_address;
	104
	105	cell->vl_addrs[cell->vl_naddrs++].s_addr =
	106	htonl((a << 24) \| (b << 16) \| (c << 8) \| d);
	107
	108	} while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
	109
	110	/* create a key to represent an anonymous user */
	111	memcpy(keyname, "afs@", 4);
	112	dp = keyname + 4;
	113	cp = cell->name;
	114	do {
	115	dp++ = toupper(cp);
	116	} while (*cp++);
	117
	118	key = rxrpc_get_null_key(keyname);
	119	if (IS_ERR(key)) {
	120	_debug("no key");
	121	ret = PTR_ERR(key);
	122	goto error;
	123	}
	124	cell->anonymous_key = key;
	125
	126	_debug("anon key %p{%x}",
	127	cell->anonymous_key, key_serial(cell->anonymous_key));
	128
	129	_leave(" = %p", cell);
	130	return cell;
	131
	132	bad_address:
	133	printk(KERN_ERR "kAFS: bad VL server IP address\n");
	134	ret = -EINVAL;
	135	error:
	136	key_put(cell->anonymous_key);
	137	kfree(dvllist);
	138	kfree(cell);
	139	_leave(" = %d", ret);
	140	return ERR_PTR(ret);
	141	}
	142
	143	/*
	144	* afs_cell_crate() - create a cell record
	145	* @name: is the name of the cell.
	146	* @namsesz: is the strlen of the cell name.
	147	* @vllist: is a colon separated list of IP addresses in "a.b.c.d" format.
	148	* @retref: is T to return the cell reference when the cell exists.
	149	*/
	150	struct afs_cell afs_cell_create(const char name, unsigned namesz,
	151	char *vllist, bool retref)
	152	{
	153	struct afs_cell *cell;
	154	int ret;
	155
	156	_enter("%.s,%s", namesz, namesz, name ?: "", vllist);
	157
	158	down_write(&afs_cells_sem);
	159	read_lock(&afs_cells_lock);
	160	list_for_each_entry(cell, &afs_cells, link) {
	161	if (strncasecmp(cell->name, name, namesz) == 0)
	162	goto duplicate_name;
	163	}
	164	read_unlock(&afs_cells_lock);
	165
	166	cell = afs_cell_alloc(name, namesz, vllist);
	167	if (IS_ERR(cell)) {
	168	_leave(" = %ld", PTR_ERR(cell));
	169	up_write(&afs_cells_sem);
	170	return cell;
	171	}
	172
	173	/* add a proc directory for this cell */
	174	ret = afs_proc_cell_setup(cell);
	175	if (ret < 0)
	176	goto error;
	177
	178	#ifdef CONFIG_AFS_FSCACHE
	179	/* put it up for caching (this never returns an error) */
	180	cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
	181	&afs_cell_cache_index_def,
	182	cell, true);
	183	#endif
	184
	185	/* add to the cell lists */
	186	write_lock(&afs_cells_lock);
	187	list_add_tail(&cell->link, &afs_cells);
	188	write_unlock(&afs_cells_lock);
	189
	190	down_write(&afs_proc_cells_sem);
	191	list_add_tail(&cell->proc_link, &afs_proc_cells);
	192	up_write(&afs_proc_cells_sem);
	193	up_write(&afs_cells_sem);
	194
	195	_leave(" = %p", cell);
	196	return cell;
	197
	198	error:
	199	up_write(&afs_cells_sem);
	200	key_put(cell->anonymous_key);
	201	kfree(cell);
	202	_leave(" = %d", ret);
	203	return ERR_PTR(ret);
	204
	205	duplicate_name:
	206	if (retref && !IS_ERR(cell))
	207	afs_get_cell(cell);
	208
	209	read_unlock(&afs_cells_lock);
	210	up_write(&afs_cells_sem);
	211
	212	if (retref) {
	213	_leave(" = %p", cell);
	214	return cell;
	215	}
	216
	217	_leave(" = -EEXIST");
	218	return ERR_PTR(-EEXIST);
	219	}
	220
	221	/*
	222	* set the root cell information
	223	* - can be called with a module parameter string
	224	* - can be called from a write to /proc/fs/afs/rootcell
	225	*/
	226	int afs_cell_init(char *rootcell)
	227	{
	228	struct afs_cell old_root, new_root;
	229	char *cp;
	230
	231	_enter("");
	232
	233	if (!rootcell) {
	234	/* module is loaded with no parameters, or built statically.
	235	* - in the future we might initialize cell DB here.
	236	*/
	237	_leave(" = 0 [no root]");
	238	return 0;
	239	}
	240
	241	cp = strchr(rootcell, ':');
	242	if (!cp)
	243	_debug("kAFS: no VL server IP addresses specified");
	244	else
	245	*cp++ = 0;
	246
	247	/* allocate a cell record for the root cell */
	248	new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
	249	if (IS_ERR(new_root)) {
	250	_leave(" = %ld", PTR_ERR(new_root));
	251	return PTR_ERR(new_root);
	252	}
	253
	254	/* install the new cell */
	255	write_lock(&afs_cells_lock);
	256	old_root = afs_cell_root;
	257	afs_cell_root = new_root;
	258	write_unlock(&afs_cells_lock);
	259	afs_put_cell(old_root);
	260
	261	_leave(" = 0");
	262	return 0;
	263	}
	264
	265	/*
	266	* lookup a cell record
	267	*/
	268	struct afs_cell afs_cell_lookup(const char name, unsigned namesz,
	269	bool dns_cell)
	270	{
	271	struct afs_cell *cell;
	272
	273	_enter("\"%.s\",", namesz, namesz, name ?: "");
	274
	275	down_read(&afs_cells_sem);
	276	read_lock(&afs_cells_lock);
	277
	278	if (name) {
	279	/* if the cell was named, look for it in the cell record list */
	280	list_for_each_entry(cell, &afs_cells, link) {
	281	if (strncmp(cell->name, name, namesz) == 0) {
	282	afs_get_cell(cell);
	283	goto found;
	284	}
	285	}
	286	cell = ERR_PTR(-ENOENT);
	287	if (dns_cell)
	288	goto create_cell;
	289	found:
	290	;
	291	} else {
	292	cell = afs_cell_root;
	293	if (!cell) {
	294	/* this should not happen unless user tries to mount
	295	* when root cell is not set. Return an impossibly
	296	* bizarre errno to alert the user. Things like
	297	* ENOENT might be "more appropriate" but they happen
	298	* for other reasons.
	299	*/
	300	cell = ERR_PTR(-EDESTADDRREQ);
	301	} else {
	302	afs_get_cell(cell);
	303	}
	304
	305	}
	306
	307	read_unlock(&afs_cells_lock);
	308	up_read(&afs_cells_sem);
	309	_leave(" = %p", cell);
	310	return cell;
	311
	312	create_cell:
	313	read_unlock(&afs_cells_lock);
	314	up_read(&afs_cells_sem);
	315
	316	cell = afs_cell_create(name, namesz, NULL, true);
	317
	318	_leave(" = %p", cell);
	319	return cell;
	320	}
	321
	322	#if 0
	323	/*
	324	* try and get a cell record
	325	*/
	326	struct afs_cell afs_get_cell_maybe(struct afs_cell cell)
	327	{
	328	write_lock(&afs_cells_lock);
	329
	330	if (cell && !list_empty(&cell->link))
	331	afs_get_cell(cell);
	332	else
	333	cell = NULL;
	334
	335	write_unlock(&afs_cells_lock);
	336	return cell;
	337	}
	338	#endif /* 0 */
	339
	340	/*
	341	* destroy a cell record
	342	*/
	343	void afs_put_cell(struct afs_cell *cell)
	344	{
	345	if (!cell)
	346	return;
	347
	348	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
	349
	350	ASSERTCMP(atomic_read(&cell->usage), >, 0);
	351
	352	/* to prevent a race, the decrement and the dequeue must be effectively
	353	* atomic */
	354	write_lock(&afs_cells_lock);
	355
	356	if (likely(!atomic_dec_and_test(&cell->usage))) {
	357	write_unlock(&afs_cells_lock);
	358	_leave("");
	359	return;
	360	}
	361
	362	ASSERT(list_empty(&cell->servers));
	363	ASSERT(list_empty(&cell->vl_list));
	364
	365	write_unlock(&afs_cells_lock);
	366
	367	wake_up(&afs_cells_freeable_wq);
	368
	369	_leave(" [unused]");
	370	}
	371
	372	/*
	373	* destroy a cell record
	374	* - must be called with the afs_cells_sem write-locked
	375	* - cell->link should have been broken by the caller
	376	*/
	377	static void afs_cell_destroy(struct afs_cell *cell)
	378	{
	379	_enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
	380
	381	ASSERTCMP(atomic_read(&cell->usage), >=, 0);
	382	ASSERT(list_empty(&cell->link));
	383
	384	/* wait for everyone to stop using the cell */
	385	if (atomic_read(&cell->usage) > 0) {
	386	DECLARE_WAITQUEUE(myself, current);
	387
	388	_debug("wait for cell %s", cell->name);
	389	set_current_state(TASK_UNINTERRUPTIBLE);
	390	add_wait_queue(&afs_cells_freeable_wq, &myself);
	391
	392	while (atomic_read(&cell->usage) > 0) {
	393	schedule();
	394	set_current_state(TASK_UNINTERRUPTIBLE);
	395	}
	396
	397	remove_wait_queue(&afs_cells_freeable_wq, &myself);
	398	set_current_state(TASK_RUNNING);
	399	}
	400
	401	_debug("cell dead");
	402	ASSERTCMP(atomic_read(&cell->usage), ==, 0);
	403	ASSERT(list_empty(&cell->servers));
	404	ASSERT(list_empty(&cell->vl_list));
	405
	406	afs_proc_cell_remove(cell);
	407
	408	down_write(&afs_proc_cells_sem);
	409	list_del_init(&cell->proc_link);
	410	up_write(&afs_proc_cells_sem);
	411
	412	#ifdef CONFIG_AFS_FSCACHE
	413	fscache_relinquish_cookie(cell->cache, 0);
	414	#endif
	415	key_put(cell->anonymous_key);
	416	kfree(cell);
	417
	418	_leave(" [destroyed]");
	419	}
	420
	421	/*
	422	* purge in-memory cell database on module unload or afs_init() failure
	423	* - the timeout daemon is stopped before calling this
	424	*/
	425	void afs_cell_purge(void)
	426	{
	427	struct afs_cell *cell;
	428
	429	_enter("");
	430
	431	afs_put_cell(afs_cell_root);
	432
	433	down_write(&afs_cells_sem);
	434
	435	while (!list_empty(&afs_cells)) {
	436	cell = NULL;
	437
	438	/* remove the next cell from the front of the list */
	439	write_lock(&afs_cells_lock);
	440
	441	if (!list_empty(&afs_cells)) {
	442	cell = list_entry(afs_cells.next,
	443	struct afs_cell, link);
	444	list_del_init(&cell->link);
	445	}
	446
	447	write_unlock(&afs_cells_lock);
	448
	449	if (cell) {
	450	_debug("PURGING CELL %s (%d)",
	451	cell->name, atomic_read(&cell->usage));
	452
	453	/* now the cell should be left with no references */
	454	afs_cell_destroy(cell);
	455	}
	456	}
	457
	458	up_write(&afs_cells_sem);
	459	_leave("");
	460	}