https://github.com/torvalds/linux
Tip revision: 4cece764965020c22cff7665b18a012006359095 authored by Linus Torvalds on 24 March 2024, 21:10:05 UTC
Linux 6.9-rc1
Linux 6.9-rc1
Tip revision: 4cece76
vl_alias.c
// 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;
}