fs/afs/volume.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* AFS volume management
  *
  * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

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

 unsigned __read_mostly afs_volume_gc_delay = 10;
 unsigned __read_mostly afs_volume_record_life = 60 * 60;

 /*
  * Insert a volume into a cell.  If there's an existing volume record, that is
  * returned instead with a ref held.
  */
 static struct afs_volume *afs_insert_volume_into_cell(struct afs_cell *cell,
 						      struct afs_volume *volume)
 {
 	struct afs_volume *p;
 	struct rb_node *parent = NULL, **pp;

 	write_seqlock(&cell->volume_lock);

 	pp = &cell->volumes.rb_node;
 	while (*pp) {
 		parent = *pp;
 		p = rb_entry(parent, struct afs_volume, cell_node);
 		if (p->vid < volume->vid) {
 			pp = &(*pp)->rb_left;
 		} else if (p->vid > volume->vid) {
 			pp = &(*pp)->rb_right;
 		} else {
 			volume = afs_get_volume(p, afs_volume_trace_get_cell_insert);
 			goto found;
 		}
 	}

 	rb_link_node_rcu(&volume->cell_node, parent, pp);
 	rb_insert_color(&volume->cell_node, &cell->volumes);
 	hlist_add_head_rcu(&volume->proc_link, &cell->proc_volumes);

 found:
 	write_sequnlock(&cell->volume_lock);
 	return volume;

 }

 static void afs_remove_volume_from_cell(struct afs_volume *volume)
 {
 	struct afs_cell *cell = volume->cell;

 	if (!hlist_unhashed(&volume->proc_link)) {
 		trace_afs_volume(volume->vid, atomic_read(&volume->usage),
 				 afs_volume_trace_remove);
 		write_seqlock(&cell->volume_lock);
 		hlist_del_rcu(&volume->proc_link);
 		rb_erase(&volume->cell_node, &cell->volumes);
 		write_sequnlock(&cell->volume_lock);
 	}
 }

 /*
  * Allocate a volume record and load it up from a vldb record.
  */
 static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 					   struct afs_vldb_entry *vldb,
 					   unsigned long type_mask)
 {
 	struct afs_server_list *slist;
 	struct afs_volume *volume;
 	int ret = -ENOMEM, nr_servers = 0, i;

 	for (i = 0; i < vldb->nr_servers; i++)
 		if (vldb->fs_mask[i] & type_mask)
 			nr_servers++;

 	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
 	if (!volume)
 		goto error_0;

 	volume->vid		= vldb->vid[params->type];
 	volume->update_at	= ktime_get_real_seconds() + afs_volume_record_life;
 	volume->cell		= afs_get_cell(params->cell, afs_cell_trace_get_vol);
 	volume->type		= params->type;
 	volume->type_force	= params->force;
 	volume->name_len	= vldb->name_len;

 	atomic_set(&volume->usage, 1);
 	INIT_HLIST_NODE(&volume->proc_link);
 	rwlock_init(&volume->servers_lock);
 	rwlock_init(&volume->cb_v_break_lock);
 	memcpy(volume->name, vldb->name, vldb->name_len + 1);

 	slist = afs_alloc_server_list(params->cell, params->key, vldb, type_mask);
 	if (IS_ERR(slist)) {
 		ret = PTR_ERR(slist);
 		goto error_1;
 	}

 	refcount_set(&slist->usage, 1);
 	rcu_assign_pointer(volume->servers, slist);
 	trace_afs_volume(volume->vid, 1, afs_volume_trace_alloc);
 	return volume;

 error_1:
 	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
 	kfree(volume);
 error_0:
 	return ERR_PTR(ret);
 }

 /*
  * Look up or allocate a volume record.
  */
 static struct afs_volume *afs_lookup_volume(struct afs_fs_context *params,
 					    struct afs_vldb_entry *vldb,
 					    unsigned long type_mask)
 {
 	struct afs_volume *candidate, *volume;

 	candidate = afs_alloc_volume(params, vldb, type_mask);
 	if (IS_ERR(candidate))
 		return candidate;

 	volume = afs_insert_volume_into_cell(params->cell, candidate);
 	if (volume != candidate)
 		afs_put_volume(params->net, candidate, afs_volume_trace_put_cell_dup);
 	return volume;
 }

 /*
  * Look up a VLDB record for a volume.
  */
 static struct afs_vldb_entry *afs_vl_lookup_vldb(struct afs_cell *cell,
 						 struct key *key,
 						 const char *volname,
 						 size_t volnamesz)
 {
 	struct afs_vldb_entry *vldb = ERR_PTR(-EDESTADDRREQ);
 	struct afs_vl_cursor vc;
 	int ret;

 	if (!afs_begin_vlserver_operation(&vc, cell, key))
 		return ERR_PTR(-ERESTARTSYS);

 	while (afs_select_vlserver(&vc)) {
 		vldb = afs_vl_get_entry_by_name_u(&vc, volname, volnamesz);
 	}

 	ret = afs_end_vlserver_operation(&vc);
 	return ret < 0 ? ERR_PTR(ret) : vldb;
 }

 /*
  * Look up a volume in the VL server and create a candidate volume record for
  * it.
  *
  * The volume name can be one of the following:
  *	"%[cell:]volume[.]"		R/W volume
  *	"#[cell:]volume[.]"		R/O or R/W volume (rwparent=0),
  *					 or R/W (rwparent=1) volume
  *	"%[cell:]volume.readonly"	R/O volume
  *	"#[cell:]volume.readonly"	R/O volume
  *	"%[cell:]volume.backup"		Backup volume
  *	"#[cell:]volume.backup"		Backup volume
  *
  * The cell name is optional, and defaults to the current cell.
  *
  * See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
  * Guide
  * - Rule 1: Explicit type suffix forces access of that type or nothing
  *           (no suffix, then use Rule 2 & 3)
  * - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
  *           if not available
  * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
  *           explicitly told otherwise
  */
 struct afs_volume *afs_create_volume(struct afs_fs_context *params)
 {
 	struct afs_vldb_entry *vldb;
 	struct afs_volume *volume;
 	unsigned long type_mask = 1UL << params->type;

 	vldb = afs_vl_lookup_vldb(params->cell, params->key,
 				  params->volname, params->volnamesz);
 	if (IS_ERR(vldb))
 		return ERR_CAST(vldb);

 	if (test_bit(AFS_VLDB_QUERY_ERROR, &vldb->flags)) {
 		volume = ERR_PTR(vldb->error);
 		goto error;
 	}

 	/* Make the final decision on the type we want */
 	volume = ERR_PTR(-ENOMEDIUM);
 	if (params->force) {
 		if (!(vldb->flags & type_mask))
 			goto error;
 	} else if (test_bit(AFS_VLDB_HAS_RO, &vldb->flags)) {
 		params->type = AFSVL_ROVOL;
 	} else if (test_bit(AFS_VLDB_HAS_RW, &vldb->flags)) {
 		params->type = AFSVL_RWVOL;
 	} else {
 		goto error;
 	}

 	type_mask = 1UL << params->type;
 	volume = afs_lookup_volume(params, vldb, type_mask);

 error:
 	kfree(vldb);
 	return volume;
 }

 /*
  * Destroy a volume record
  */
 static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
 {
 	_enter("%p", volume);

 #ifdef CONFIG_AFS_FSCACHE
 	ASSERTCMP(volume->cache, ==, NULL);
 #endif

 	afs_remove_volume_from_cell(volume);
 	afs_put_serverlist(net, rcu_access_pointer(volume->servers));
 	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
 	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
 			 afs_volume_trace_free);
 	kfree_rcu(volume, rcu);

 	_leave(" [destroyed]");
 }

 /*
  * Get a reference on a volume record.
  */
 struct afs_volume *afs_get_volume(struct afs_volume *volume,
 				  enum afs_volume_trace reason)
 {
 	if (volume) {
 		int u = atomic_inc_return(&volume->usage);
 		trace_afs_volume(volume->vid, u, reason);
 	}
 	return volume;
 }


 /*
  * Drop a reference on a volume record.
  */
 void afs_put_volume(struct afs_net *net, struct afs_volume *volume,
 		    enum afs_volume_trace reason)
 {
 	if (volume) {
 		afs_volid_t vid = volume->vid;
 		int u = atomic_dec_return(&volume->usage);
 		trace_afs_volume(vid, u, reason);
 		if (u == 0)
 			afs_destroy_volume(net, volume);
 	}
 }

 /*
  * Activate a volume.
  */
 void afs_activate_volume(struct afs_volume *volume)
 {
 #ifdef CONFIG_AFS_FSCACHE
 	volume->cache = fscache_acquire_cookie(volume->cell->cache,
 					       &afs_volume_cache_index_def,
 					       &volume->vid, sizeof(volume->vid),
 					       NULL, 0,
 					       volume, 0, true);
 #endif
 }

 /*
  * Deactivate a volume.
  */
 void afs_deactivate_volume(struct afs_volume *volume)
 {
 	_enter("%s", volume->name);

 #ifdef CONFIG_AFS_FSCACHE
 	fscache_relinquish_cookie(volume->cache, NULL,
 				  test_bit(AFS_VOLUME_DELETED, &volume->flags));
 	volume->cache = NULL;
 #endif

 	_leave("");
 }

 /*
  * Query the VL service to update the volume status.
  */
 static int afs_update_volume_status(struct afs_volume *volume, struct key *key)
 {
 	struct afs_server_list *new, *old, *discard;
 	struct afs_vldb_entry *vldb;
 	char idbuf[16];
 	int ret, idsz;

 	_enter("");

 	/* We look up an ID by passing it as a decimal string in the
 	 * operation's name parameter.
 	 */
 	idsz = sprintf(idbuf, "%llu", volume->vid);

 	vldb = afs_vl_lookup_vldb(volume->cell, key, idbuf, idsz);
 	if (IS_ERR(vldb)) {
 		ret = PTR_ERR(vldb);
 		goto error;
 	}

 	/* See if the volume got renamed. */
 	if (vldb->name_len != volume->name_len ||
 	    memcmp(vldb->name, volume->name, vldb->name_len) != 0) {
 		/* TODO: Use RCU'd string. */
 		memcpy(volume->name, vldb->name, AFS_MAXVOLNAME);
 		volume->name_len = vldb->name_len;
 	}

 	/* See if the volume's server list got updated. */
 	new = afs_alloc_server_list(volume->cell, key,
 				    vldb, (1 << volume->type));
 	if (IS_ERR(new)) {
 		ret = PTR_ERR(new);
 		goto error_vldb;
 	}

 	write_lock(&volume->servers_lock);

 	discard = new;
 	old = rcu_dereference_protected(volume->servers,
 					lockdep_is_held(&volume->servers_lock));
 	if (afs_annotate_server_list(new, old)) {
 		new->seq = volume->servers_seq + 1;
 		rcu_assign_pointer(volume->servers, new);
 		smp_wmb();
 		volume->servers_seq++;
 		discard = old;
 	}

 	volume->update_at = ktime_get_real_seconds() + afs_volume_record_life;
 	write_unlock(&volume->servers_lock);
 	ret = 0;

 	afs_put_serverlist(volume->cell->net, discard);
 error_vldb:
 	kfree(vldb);
 error:
 	_leave(" = %d", ret);
 	return ret;
 }

 /*
  * Make sure the volume record is up to date.
  */
 int afs_check_volume_status(struct afs_volume *volume, struct afs_operation *op)
 {
 	int ret, retries = 0;

 	_enter("");

 retry:
 	if (test_bit(AFS_VOLUME_WAIT, &volume->flags))
 		goto wait;
 	if (volume->update_at <= ktime_get_real_seconds() ||
 	    test_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags))
 		goto update;
 	_leave(" = 0");
 	return 0;

 update:
 	if (!test_and_set_bit_lock(AFS_VOLUME_UPDATING, &volume->flags)) {
 		clear_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
 		ret = afs_update_volume_status(volume, op->key);
 		if (ret < 0)
 			set_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
 		clear_bit_unlock(AFS_VOLUME_WAIT, &volume->flags);
 		clear_bit_unlock(AFS_VOLUME_UPDATING, &volume->flags);
 		wake_up_bit(&volume->flags, AFS_VOLUME_WAIT);
 		_leave(" = %d", ret);
 		return ret;
 	}

 wait:
 	if (!test_bit(AFS_VOLUME_WAIT, &volume->flags)) {
 		_leave(" = 0 [no wait]");
 		return 0;
 	}

 	ret = wait_on_bit(&volume->flags, AFS_VOLUME_WAIT,
 			  (op->flags & AFS_OPERATION_UNINTR) ?
 			  TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
 	if (ret == -ERESTARTSYS) {
 		_leave(" = %d", ret);
 		return ret;
 	}

 	retries++;
 	if (retries == 4) {
 		_leave(" = -ESTALE");
 		return -ESTALE;
 	}
 	goto retry;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* AFS volume management
	*
	* Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

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

	unsigned __read_mostly afs_volume_gc_delay = 10;
	unsigned __read_mostly afs_volume_record_life = 60 * 60;

	/*
	* Insert a volume into a cell. If there's an existing volume record, that is
	* returned instead with a ref held.
	*/
	static struct afs_volume afs_insert_volume_into_cell(struct afs_cell cell,
	struct afs_volume *volume)
	{
	struct afs_volume *p;
	struct rb_node parent = NULL, *pp;

	write_seqlock(&cell->volume_lock);

	pp = &cell->volumes.rb_node;
	while (*pp) {
	parent = *pp;
	p = rb_entry(parent, struct afs_volume, cell_node);
	if (p->vid < volume->vid) {
	pp = &(*pp)->rb_left;
	} else if (p->vid > volume->vid) {
	pp = &(*pp)->rb_right;
	} else {
	volume = afs_get_volume(p, afs_volume_trace_get_cell_insert);
	goto found;
	}
	}

	rb_link_node_rcu(&volume->cell_node, parent, pp);
	rb_insert_color(&volume->cell_node, &cell->volumes);
	hlist_add_head_rcu(&volume->proc_link, &cell->proc_volumes);

	found:
	write_sequnlock(&cell->volume_lock);
	return volume;

	}

	static void afs_remove_volume_from_cell(struct afs_volume *volume)
	{
	struct afs_cell *cell = volume->cell;

	if (!hlist_unhashed(&volume->proc_link)) {
	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
	afs_volume_trace_remove);
	write_seqlock(&cell->volume_lock);
	hlist_del_rcu(&volume->proc_link);
	rb_erase(&volume->cell_node, &cell->volumes);
	write_sequnlock(&cell->volume_lock);
	}
	}

	/*
	* Allocate a volume record and load it up from a vldb record.
	*/
	static struct afs_volume afs_alloc_volume(struct afs_fs_context params,
	struct afs_vldb_entry *vldb,
	unsigned long type_mask)
	{
	struct afs_server_list *slist;
	struct afs_volume *volume;
	int ret = -ENOMEM, nr_servers = 0, i;

	for (i = 0; i < vldb->nr_servers; i++)
	if (vldb->fs_mask[i] & type_mask)
	nr_servers++;

	volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
	if (!volume)
	goto error_0;

	volume->vid = vldb->vid[params->type];
	volume->update_at = ktime_get_real_seconds() + afs_volume_record_life;
	volume->cell = afs_get_cell(params->cell, afs_cell_trace_get_vol);
	volume->type = params->type;
	volume->type_force = params->force;
	volume->name_len = vldb->name_len;

	atomic_set(&volume->usage, 1);
	INIT_HLIST_NODE(&volume->proc_link);
	rwlock_init(&volume->servers_lock);
	rwlock_init(&volume->cb_v_break_lock);
	memcpy(volume->name, vldb->name, vldb->name_len + 1);

	slist = afs_alloc_server_list(params->cell, params->key, vldb, type_mask);
	if (IS_ERR(slist)) {
	ret = PTR_ERR(slist);
	goto error_1;
	}

	refcount_set(&slist->usage, 1);
	rcu_assign_pointer(volume->servers, slist);
	trace_afs_volume(volume->vid, 1, afs_volume_trace_alloc);
	return volume;

	error_1:
	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
	kfree(volume);
	error_0:
	return ERR_PTR(ret);
	}

	/*
	* Look up or allocate a volume record.
	*/
	static struct afs_volume afs_lookup_volume(struct afs_fs_context params,
	struct afs_vldb_entry *vldb,
	unsigned long type_mask)
	{
	struct afs_volume candidate, volume;

	candidate = afs_alloc_volume(params, vldb, type_mask);
	if (IS_ERR(candidate))
	return candidate;

	volume = afs_insert_volume_into_cell(params->cell, candidate);
	if (volume != candidate)
	afs_put_volume(params->net, candidate, afs_volume_trace_put_cell_dup);
	return volume;
	}

	/*
	* Look up a VLDB record for a volume.
	*/
	static struct afs_vldb_entry afs_vl_lookup_vldb(struct afs_cell cell,
	struct key *key,
	const char *volname,
	size_t volnamesz)
	{
	struct afs_vldb_entry *vldb = ERR_PTR(-EDESTADDRREQ);
	struct afs_vl_cursor vc;
	int ret;

	if (!afs_begin_vlserver_operation(&vc, cell, key))
	return ERR_PTR(-ERESTARTSYS);

	while (afs_select_vlserver(&vc)) {
	vldb = afs_vl_get_entry_by_name_u(&vc, volname, volnamesz);
	}

	ret = afs_end_vlserver_operation(&vc);
	return ret < 0 ? ERR_PTR(ret) : vldb;
	}

	/*
	* Look up a volume in the VL server and create a candidate volume record for
	* it.
	*
	* The volume name can be one of the following:
	* "%[cell:]volume[.]" R/W volume
	* "#[cell:]volume[.]" R/O or R/W volume (rwparent=0),
	* or R/W (rwparent=1) volume
	* "%[cell:]volume.readonly" R/O volume
	* "#[cell:]volume.readonly" R/O volume
	* "%[cell:]volume.backup" Backup volume
	* "#[cell:]volume.backup" Backup volume
	*
	* The cell name is optional, and defaults to the current cell.
	*
	* See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
	* Guide
	* - Rule 1: Explicit type suffix forces access of that type or nothing
	* (no suffix, then use Rule 2 & 3)
	* - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
	* if not available
	* - Rule 3: If parent volume is R/W, then only mount R/W volume unless
	* explicitly told otherwise
	*/
	struct afs_volume afs_create_volume(struct afs_fs_context params)
	{
	struct afs_vldb_entry *vldb;
	struct afs_volume *volume;
	unsigned long type_mask = 1UL << params->type;

	vldb = afs_vl_lookup_vldb(params->cell, params->key,
	params->volname, params->volnamesz);
	if (IS_ERR(vldb))
	return ERR_CAST(vldb);

	if (test_bit(AFS_VLDB_QUERY_ERROR, &vldb->flags)) {
	volume = ERR_PTR(vldb->error);
	goto error;
	}

	/* Make the final decision on the type we want */
	volume = ERR_PTR(-ENOMEDIUM);
	if (params->force) {
	if (!(vldb->flags & type_mask))
	goto error;
	} else if (test_bit(AFS_VLDB_HAS_RO, &vldb->flags)) {
	params->type = AFSVL_ROVOL;
	} else if (test_bit(AFS_VLDB_HAS_RW, &vldb->flags)) {
	params->type = AFSVL_RWVOL;
	} else {
	goto error;
	}

	type_mask = 1UL << params->type;
	volume = afs_lookup_volume(params, vldb, type_mask);

	error:
	kfree(vldb);
	return volume;
	}

	/*
	* Destroy a volume record
	*/
	static void afs_destroy_volume(struct afs_net net, struct afs_volume volume)
	{
	_enter("%p", volume);

	#ifdef CONFIG_AFS_FSCACHE
	ASSERTCMP(volume->cache, ==, NULL);
	#endif

	afs_remove_volume_from_cell(volume);
	afs_put_serverlist(net, rcu_access_pointer(volume->servers));
	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
	afs_volume_trace_free);
	kfree_rcu(volume, rcu);

	_leave(" [destroyed]");
	}

	/*
	* Get a reference on a volume record.
	*/
	struct afs_volume afs_get_volume(struct afs_volume volume,
	enum afs_volume_trace reason)
	{
	if (volume) {
	int u = atomic_inc_return(&volume->usage);
	trace_afs_volume(volume->vid, u, reason);
	}
	return volume;
	}


	/*
	* Drop a reference on a volume record.
	*/
	void afs_put_volume(struct afs_net net, struct afs_volume volume,
	enum afs_volume_trace reason)
	{
	if (volume) {
	afs_volid_t vid = volume->vid;
	int u = atomic_dec_return(&volume->usage);
	trace_afs_volume(vid, u, reason);
	if (u == 0)
	afs_destroy_volume(net, volume);
	}
	}

	/*
	* Activate a volume.
	*/
	void afs_activate_volume(struct afs_volume *volume)
	{
	#ifdef CONFIG_AFS_FSCACHE
	volume->cache = fscache_acquire_cookie(volume->cell->cache,
	&afs_volume_cache_index_def,
	&volume->vid, sizeof(volume->vid),
	NULL, 0,
	volume, 0, true);
	#endif
	}

	/*
	* Deactivate a volume.
	*/
	void afs_deactivate_volume(struct afs_volume *volume)
	{
	_enter("%s", volume->name);

	#ifdef CONFIG_AFS_FSCACHE
	fscache_relinquish_cookie(volume->cache, NULL,
	test_bit(AFS_VOLUME_DELETED, &volume->flags));
	volume->cache = NULL;
	#endif

	_leave("");
	}

	/*
	* Query the VL service to update the volume status.
	*/
	static int afs_update_volume_status(struct afs_volume volume, struct key key)
	{
	struct afs_server_list new, old, *discard;
	struct afs_vldb_entry *vldb;
	char idbuf[16];
	int ret, idsz;

	_enter("");

	/* We look up an ID by passing it as a decimal string in the
	* operation's name parameter.
	*/
	idsz = sprintf(idbuf, "%llu", volume->vid);

	vldb = afs_vl_lookup_vldb(volume->cell, key, idbuf, idsz);
	if (IS_ERR(vldb)) {
	ret = PTR_ERR(vldb);
	goto error;
	}

	/* See if the volume got renamed. */
	if (vldb->name_len != volume->name_len \|\|
	memcmp(vldb->name, volume->name, vldb->name_len) != 0) {
	/* TODO: Use RCU'd string. */
	memcpy(volume->name, vldb->name, AFS_MAXVOLNAME);
	volume->name_len = vldb->name_len;
	}

	/* See if the volume's server list got updated. */
	new = afs_alloc_server_list(volume->cell, key,
	vldb, (1 << volume->type));
	if (IS_ERR(new)) {
	ret = PTR_ERR(new);
	goto error_vldb;
	}

	write_lock(&volume->servers_lock);

	discard = new;
	old = rcu_dereference_protected(volume->servers,
	lockdep_is_held(&volume->servers_lock));
	if (afs_annotate_server_list(new, old)) {
	new->seq = volume->servers_seq + 1;
	rcu_assign_pointer(volume->servers, new);
	smp_wmb();
	volume->servers_seq++;
	discard = old;
	}

	volume->update_at = ktime_get_real_seconds() + afs_volume_record_life;
	write_unlock(&volume->servers_lock);
	ret = 0;

	afs_put_serverlist(volume->cell->net, discard);
	error_vldb:
	kfree(vldb);
	error:
	_leave(" = %d", ret);
	return ret;
	}

	/*
	* Make sure the volume record is up to date.
	*/
	int afs_check_volume_status(struct afs_volume volume, struct afs_operation op)
	{
	int ret, retries = 0;

	_enter("");

	retry:
	if (test_bit(AFS_VOLUME_WAIT, &volume->flags))
	goto wait;
	if (volume->update_at <= ktime_get_real_seconds() \|\|
	test_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags))
	goto update;
	_leave(" = 0");
	return 0;

	update:
	if (!test_and_set_bit_lock(AFS_VOLUME_UPDATING, &volume->flags)) {
	clear_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
	ret = afs_update_volume_status(volume, op->key);
	if (ret < 0)
	set_bit(AFS_VOLUME_NEEDS_UPDATE, &volume->flags);
	clear_bit_unlock(AFS_VOLUME_WAIT, &volume->flags);
	clear_bit_unlock(AFS_VOLUME_UPDATING, &volume->flags);
	wake_up_bit(&volume->flags, AFS_VOLUME_WAIT);
	_leave(" = %d", ret);
	return ret;
	}

	wait:
	if (!test_bit(AFS_VOLUME_WAIT, &volume->flags)) {
	_leave(" = 0 [no wait]");
	return 0;
	}

	ret = wait_on_bit(&volume->flags, AFS_VOLUME_WAIT,
	(op->flags & AFS_OPERATION_UNINTR) ?
	TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
	if (ret == -ERESTARTSYS) {
	_leave(" = %d", ret);
	return ret;
	}

	retries++;
	if (retries == 4) {
	_leave(" = -ESTALE");
	return -ESTALE;
	}
	goto retry;
	}