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

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* AFS cell alias detection
  *
  * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */

 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/namei.h>
 #include <keys/rxrpc-type.h>
 #include "internal.h"

 /*
  * Sample a volume.
  */
 static struct afs_volume *afs_sample_volume(struct afs_cell *cell, struct key *key,
 					    const char *name, unsigned int namelen)
 {
 	struct afs_volume *volume;
 	struct afs_fs_context fc = {
 		.type		= 0, /* Explicitly leave it to the VLDB */
 		.volnamesz	= namelen,
 		.volname	= name,
 		.net		= cell->net,
 		.cell		= cell,
 		.key		= key, /* This might need to be something */
 	};

 	volume = afs_create_volume(&fc);
 	_leave(" = %p", volume);
 	return volume;
 }

 /*
  * Compare the address lists of a pair of fileservers.
  */
 static int afs_compare_fs_alists(const struct afs_server *server_a,
 				 const struct afs_server *server_b)
 {
 	const struct afs_addr_list *la, *lb;
 	int a = 0, b = 0, addr_matches = 0;

 	la = rcu_dereference(server_a->endpoint_state)->addresses;
 	lb = rcu_dereference(server_b->endpoint_state)->addresses;

 	while (a < la->nr_addrs && b < lb->nr_addrs) {
 		unsigned long pa = (unsigned long)la->addrs[a].peer;
 		unsigned long pb = (unsigned long)lb->addrs[b].peer;
 		long diff = pa - pb;

 		if (diff < 0) {
 			a++;
 		} else if (diff > 0) {
 			b++;
 		} else {
 			addr_matches++;
 			a++;
 			b++;
 		}
 	}

 	return addr_matches;
 }

 /*
  * Compare the fileserver lists of two volumes.  The server lists are sorted in
  * order of ascending UUID.
  */
 static int afs_compare_volume_slists(const struct afs_volume *vol_a,
 				     const struct afs_volume *vol_b)
 {
 	const struct afs_server_list *la, *lb;
 	int i, a = 0, b = 0, uuid_matches = 0, addr_matches = 0;

 	la = rcu_dereference(vol_a->servers);
 	lb = rcu_dereference(vol_b->servers);

 	for (i = 0; i < AFS_MAXTYPES; i++)
 		if (vol_a->vids[i] != vol_b->vids[i])
 			return 0;

 	while (a < la->nr_servers && b < lb->nr_servers) {
 		const struct afs_server *server_a = la->servers[a].server;
 		const struct afs_server *server_b = lb->servers[b].server;
 		int diff = memcmp(&server_a->uuid, &server_b->uuid, sizeof(uuid_t));

 		if (diff < 0) {
 			a++;
 		} else if (diff > 0) {
 			b++;
 		} else {
 			uuid_matches++;
 			addr_matches += afs_compare_fs_alists(server_a, server_b);
 			a++;
 			b++;
 		}
 	}

 	_leave(" = %d [um %d]", addr_matches, uuid_matches);
 	return addr_matches;
 }

 /*
  * Compare root.cell volumes.
  */
 static int afs_compare_cell_roots(struct afs_cell *cell)
 {
 	struct afs_cell *p;

 	_enter("");

 	rcu_read_lock();

 	hlist_for_each_entry_rcu(p, &cell->net->proc_cells, proc_link) {
 		if (p == cell || p->alias_of)
 			continue;
 		if (!p->root_volume)
 			continue; /* Ignore cells that don't have a root.cell volume. */

 		if (afs_compare_volume_slists(cell->root_volume, p->root_volume) != 0)
 			goto is_alias;
 	}

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

 is_alias:
 	rcu_read_unlock();
 	cell->alias_of = afs_use_cell(p, afs_cell_trace_use_alias);
 	return 1;
 }

 /*
  * Query the new cell for a volume from a cell we're already using.
  */
 static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
 				   struct afs_cell *p)
 {
 	struct afs_volume *volume, *pvol = NULL;
 	int ret;

 	/* Arbitrarily pick a volume from the list. */
 	read_seqlock_excl(&p->volume_lock);
 	if (!RB_EMPTY_ROOT(&p->volumes))
 		pvol = afs_get_volume(rb_entry(p->volumes.rb_node,
 					       struct afs_volume, cell_node),
 				      afs_volume_trace_get_query_alias);
 	read_sequnlock_excl(&p->volume_lock);
 	if (!pvol)
 		return 0;

 	_enter("%s:%s", cell->name, pvol->name);

 	/* And see if it's in the new cell. */
 	volume = afs_sample_volume(cell, key, pvol->name, pvol->name_len);
 	if (IS_ERR(volume)) {
 		afs_put_volume(pvol, afs_volume_trace_put_query_alias);
 		if (PTR_ERR(volume) != -ENOMEDIUM)
 			return PTR_ERR(volume);
 		/* That volume is not in the new cell, so not an alias */
 		return 0;
 	}

 	/* The new cell has a like-named volume also - compare volume ID,
 	 * server and address lists.
 	 */
 	ret = 0;
 	if (pvol->vid == volume->vid) {
 		rcu_read_lock();
 		if (afs_compare_volume_slists(volume, pvol))
 			ret = 1;
 		rcu_read_unlock();
 	}

 	afs_put_volume(volume, afs_volume_trace_put_query_alias);
 	afs_put_volume(pvol, afs_volume_trace_put_query_alias);
 	return ret;
 }

 /*
  * Query the new cell for volumes we know exist in cells we're already using.
  */
 static int afs_query_for_alias(struct afs_cell *cell, struct key *key)
 {
 	struct afs_cell *p;

 	_enter("%s", cell->name);

 	if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0)
 		return -ERESTARTSYS;

 	hlist_for_each_entry(p, &cell->net->proc_cells, proc_link) {
 		if (p == cell || p->alias_of)
 			continue;
 		if (RB_EMPTY_ROOT(&p->volumes))
 			continue;
 		if (p->root_volume)
 			continue; /* Ignore cells that have a root.cell volume. */
 		afs_use_cell(p, afs_cell_trace_use_check_alias);
 		mutex_unlock(&cell->net->proc_cells_lock);

 		if (afs_query_for_alias_one(cell, key, p) != 0)
 			goto is_alias;

 		if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0) {
 			afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
 			return -ERESTARTSYS;
 		}

 		afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
 	}

 	mutex_unlock(&cell->net->proc_cells_lock);
 	_leave(" = 0");
 	return 0;

 is_alias:
 	cell->alias_of = p; /* Transfer our ref */
 	return 1;
 }

 /*
  * Look up a VLDB record for a volume.
  */
 static char *afs_vl_get_cell_name(struct afs_cell *cell, struct key *key)
 {
 	struct afs_vl_cursor vc;
 	char *cell_name = ERR_PTR(-EDESTADDRREQ);
 	bool skipped = false, not_skipped = false;
 	int ret;

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

 	while (afs_select_vlserver(&vc)) {
 		if (!test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags)) {
 			vc.call_error = -EOPNOTSUPP;
 			skipped = true;
 			continue;
 		}
 		not_skipped = true;
 		cell_name = afs_yfsvl_get_cell_name(&vc);
 	}

 	ret = afs_end_vlserver_operation(&vc);
 	if (skipped && !not_skipped)
 		ret = -EOPNOTSUPP;
 	return ret < 0 ? ERR_PTR(ret) : cell_name;
 }

 static int yfs_check_canonical_cell_name(struct afs_cell *cell, struct key *key)
 {
 	struct afs_cell *master;
 	char *cell_name;

 	cell_name = afs_vl_get_cell_name(cell, key);
 	if (IS_ERR(cell_name))
 		return PTR_ERR(cell_name);

 	if (strcmp(cell_name, cell->name) == 0) {
 		kfree(cell_name);
 		return 0;
 	}

 	master = afs_lookup_cell(cell->net, cell_name, strlen(cell_name),
 				 NULL, false);
 	kfree(cell_name);
 	if (IS_ERR(master))
 		return PTR_ERR(master);

 	cell->alias_of = master; /* Transfer our ref */
 	return 1;
 }

 static int afs_do_cell_detect_alias(struct afs_cell *cell, struct key *key)
 {
 	struct afs_volume *root_volume;
 	int ret;

 	_enter("%s", cell->name);

 	ret = yfs_check_canonical_cell_name(cell, key);
 	if (ret != -EOPNOTSUPP)
 		return ret;

 	/* Try and get the root.cell volume for comparison with other cells */
 	root_volume = afs_sample_volume(cell, key, "root.cell", 9);
 	if (!IS_ERR(root_volume)) {
 		cell->root_volume = root_volume;
 		return afs_compare_cell_roots(cell);
 	}

 	if (PTR_ERR(root_volume) != -ENOMEDIUM)
 		return PTR_ERR(root_volume);

 	/* Okay, this cell doesn't have an root.cell volume.  We need to
 	 * locate some other random volume and use that to check.
 	 */
 	return afs_query_for_alias(cell, key);
 }

 /*
  * Check to see if a new cell is an alias of a cell we already have.  At this
  * point we have the cell's volume server list.
  *
  * Returns 0 if we didn't detect an alias, 1 if we found an alias and an error
  * if we had problems gathering the data required.  In the case the we did
  * detect an alias, cell->alias_of is set to point to the assumed master.
  */
 int afs_cell_detect_alias(struct afs_cell *cell, struct key *key)
 {
 	struct afs_net *net = cell->net;
 	int ret;

 	if (mutex_lock_interruptible(&net->cells_alias_lock) < 0)
 		return -ERESTARTSYS;

 	if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &cell->flags)) {
 		ret = afs_do_cell_detect_alias(cell, key);
 		if (ret >= 0)
 			clear_bit_unlock(AFS_CELL_FL_CHECK_ALIAS, &cell->flags);
 	} else {
 		ret = cell->alias_of ? 1 : 0;
 	}

 	mutex_unlock(&net->cells_alias_lock);

 	if (ret == 1)
 		pr_notice("kAFS: Cell %s is an alias of %s\n",
 			  cell->name, cell->alias_of->name);
 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* AFS cell alias detection
	*
	* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*/

	#include <linux/slab.h>
	#include <linux/sched.h>
	#include <linux/namei.h>
	#include <keys/rxrpc-type.h>
	#include "internal.h"

	/*
	* Sample a volume.
	*/
	static struct afs_volume afs_sample_volume(struct afs_cell cell, struct key *key,
	const char *name, unsigned int namelen)
	{
	struct afs_volume *volume;
	struct afs_fs_context fc = {
	.type = 0, /* Explicitly leave it to the VLDB */
	.volnamesz = namelen,
	.volname = name,
	.net = cell->net,
	.cell = cell,
	.key = key, /* This might need to be something */
	};

	volume = afs_create_volume(&fc);
	_leave(" = %p", volume);
	return volume;
	}

	/*
	* Compare the address lists of a pair of fileservers.
	*/
	static int afs_compare_fs_alists(const struct afs_server *server_a,
	const struct afs_server *server_b)
	{
	const struct afs_addr_list la, lb;
	int a = 0, b = 0, addr_matches = 0;

	la = rcu_dereference(server_a->endpoint_state)->addresses;
	lb = rcu_dereference(server_b->endpoint_state)->addresses;

	while (a < la->nr_addrs && b < lb->nr_addrs) {
	unsigned long pa = (unsigned long)la->addrs[a].peer;
	unsigned long pb = (unsigned long)lb->addrs[b].peer;
	long diff = pa - pb;

	if (diff < 0) {
	a++;
	} else if (diff > 0) {
	b++;
	} else {
	addr_matches++;
	a++;
	b++;
	}
	}

	return addr_matches;
	}

	/*
	* Compare the fileserver lists of two volumes. The server lists are sorted in
	* order of ascending UUID.
	*/
	static int afs_compare_volume_slists(const struct afs_volume *vol_a,
	const struct afs_volume *vol_b)
	{
	const struct afs_server_list la, lb;
	int i, a = 0, b = 0, uuid_matches = 0, addr_matches = 0;

	la = rcu_dereference(vol_a->servers);
	lb = rcu_dereference(vol_b->servers);

	for (i = 0; i < AFS_MAXTYPES; i++)
	if (vol_a->vids[i] != vol_b->vids[i])
	return 0;

	while (a < la->nr_servers && b < lb->nr_servers) {
	const struct afs_server *server_a = la->servers[a].server;
	const struct afs_server *server_b = lb->servers[b].server;
	int diff = memcmp(&server_a->uuid, &server_b->uuid, sizeof(uuid_t));

	if (diff < 0) {
	a++;
	} else if (diff > 0) {
	b++;
	} else {
	uuid_matches++;
	addr_matches += afs_compare_fs_alists(server_a, server_b);
	a++;
	b++;
	}
	}

	_leave(" = %d [um %d]", addr_matches, uuid_matches);
	return addr_matches;
	}

	/*
	* Compare root.cell volumes.
	*/
	static int afs_compare_cell_roots(struct afs_cell *cell)
	{
	struct afs_cell *p;

	_enter("");

	rcu_read_lock();

	hlist_for_each_entry_rcu(p, &cell->net->proc_cells, proc_link) {
	if (p == cell \|\| p->alias_of)
	continue;
	if (!p->root_volume)
	continue; /* Ignore cells that don't have a root.cell volume. */

	if (afs_compare_volume_slists(cell->root_volume, p->root_volume) != 0)
	goto is_alias;
	}

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

	is_alias:
	rcu_read_unlock();
	cell->alias_of = afs_use_cell(p, afs_cell_trace_use_alias);
	return 1;
	}

	/*
	* Query the new cell for a volume from a cell we're already using.
	*/
	static int afs_query_for_alias_one(struct afs_cell cell, struct key key,
	struct afs_cell *p)
	{
	struct afs_volume volume, pvol = NULL;
	int ret;

	/* Arbitrarily pick a volume from the list. */
	read_seqlock_excl(&p->volume_lock);
	if (!RB_EMPTY_ROOT(&p->volumes))
	pvol = afs_get_volume(rb_entry(p->volumes.rb_node,
	struct afs_volume, cell_node),
	afs_volume_trace_get_query_alias);
	read_sequnlock_excl(&p->volume_lock);
	if (!pvol)
	return 0;

	_enter("%s:%s", cell->name, pvol->name);

	/* And see if it's in the new cell. */
	volume = afs_sample_volume(cell, key, pvol->name, pvol->name_len);
	if (IS_ERR(volume)) {
	afs_put_volume(pvol, afs_volume_trace_put_query_alias);
	if (PTR_ERR(volume) != -ENOMEDIUM)
	return PTR_ERR(volume);
	/* That volume is not in the new cell, so not an alias */
	return 0;
	}

	/* The new cell has a like-named volume also - compare volume ID,
	* server and address lists.
	*/
	ret = 0;
	if (pvol->vid == volume->vid) {
	rcu_read_lock();
	if (afs_compare_volume_slists(volume, pvol))
	ret = 1;
	rcu_read_unlock();
	}

	afs_put_volume(volume, afs_volume_trace_put_query_alias);
	afs_put_volume(pvol, afs_volume_trace_put_query_alias);
	return ret;
	}

	/*
	* Query the new cell for volumes we know exist in cells we're already using.
	*/
	static int afs_query_for_alias(struct afs_cell cell, struct key key)
	{
	struct afs_cell *p;

	_enter("%s", cell->name);

	if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0)
	return -ERESTARTSYS;

	hlist_for_each_entry(p, &cell->net->proc_cells, proc_link) {
	if (p == cell \|\| p->alias_of)
	continue;
	if (RB_EMPTY_ROOT(&p->volumes))
	continue;
	if (p->root_volume)
	continue; /* Ignore cells that have a root.cell volume. */
	afs_use_cell(p, afs_cell_trace_use_check_alias);
	mutex_unlock(&cell->net->proc_cells_lock);

	if (afs_query_for_alias_one(cell, key, p) != 0)
	goto is_alias;

	if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0) {
	afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
	return -ERESTARTSYS;
	}

	afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
	}

	mutex_unlock(&cell->net->proc_cells_lock);
	_leave(" = 0");
	return 0;

	is_alias:
	cell->alias_of = p; /* Transfer our ref */
	return 1;
	}

	/*
	* Look up a VLDB record for a volume.
	*/
	static char afs_vl_get_cell_name(struct afs_cell cell, struct key *key)
	{
	struct afs_vl_cursor vc;
	char *cell_name = ERR_PTR(-EDESTADDRREQ);
	bool skipped = false, not_skipped = false;
	int ret;

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

	while (afs_select_vlserver(&vc)) {
	if (!test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags)) {
	vc.call_error = -EOPNOTSUPP;
	skipped = true;
	continue;
	}
	not_skipped = true;
	cell_name = afs_yfsvl_get_cell_name(&vc);
	}

	ret = afs_end_vlserver_operation(&vc);
	if (skipped && !not_skipped)
	ret = -EOPNOTSUPP;
	return ret < 0 ? ERR_PTR(ret) : cell_name;
	}

	static int yfs_check_canonical_cell_name(struct afs_cell cell, struct key key)
	{
	struct afs_cell *master;
	char *cell_name;

	cell_name = afs_vl_get_cell_name(cell, key);
	if (IS_ERR(cell_name))
	return PTR_ERR(cell_name);

	if (strcmp(cell_name, cell->name) == 0) {
	kfree(cell_name);
	return 0;
	}

	master = afs_lookup_cell(cell->net, cell_name, strlen(cell_name),
	NULL, false);
	kfree(cell_name);
	if (IS_ERR(master))
	return PTR_ERR(master);

	cell->alias_of = master; /* Transfer our ref */
	return 1;
	}

	static int afs_do_cell_detect_alias(struct afs_cell cell, struct key key)
	{
	struct afs_volume *root_volume;
	int ret;

	_enter("%s", cell->name);

	ret = yfs_check_canonical_cell_name(cell, key);
	if (ret != -EOPNOTSUPP)
	return ret;

	/* Try and get the root.cell volume for comparison with other cells */
	root_volume = afs_sample_volume(cell, key, "root.cell", 9);
	if (!IS_ERR(root_volume)) {
	cell->root_volume = root_volume;
	return afs_compare_cell_roots(cell);
	}

	if (PTR_ERR(root_volume) != -ENOMEDIUM)
	return PTR_ERR(root_volume);

	/* Okay, this cell doesn't have an root.cell volume. We need to
	* locate some other random volume and use that to check.
	*/
	return afs_query_for_alias(cell, key);
	}

	/*
	* Check to see if a new cell is an alias of a cell we already have. At this
	* point we have the cell's volume server list.
	*
	* Returns 0 if we didn't detect an alias, 1 if we found an alias and an error
	* if we had problems gathering the data required. In the case the we did
	* detect an alias, cell->alias_of is set to point to the assumed master.
	*/
	int afs_cell_detect_alias(struct afs_cell cell, struct key key)
	{
	struct afs_net *net = cell->net;
	int ret;

	if (mutex_lock_interruptible(&net->cells_alias_lock) < 0)
	return -ERESTARTSYS;

	if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &cell->flags)) {
	ret = afs_do_cell_detect_alias(cell, key);
	if (ret >= 0)
	clear_bit_unlock(AFS_CELL_FL_CHECK_ALIAS, &cell->flags);
	} else {
	ret = cell->alias_of ? 1 : 0;
	}

	mutex_unlock(&net->cells_alias_lock);

	if (ret == 1)
	pr_notice("kAFS: Cell %s is an alias of %s\n",
	cell->name, cell->alias_of->name);
	return ret;
	}