linux/fs/afs/server_list.c
David Howells 45df846273 afs: Fix server list handling
Fix server list handling in the following ways:

 (1) In afs_alloc_volume(), remove duplicate server list build code.  This
     was already done by afs_alloc_server_list() which afs_alloc_volume()
     previously called.  This just results in twice as many VL RPCs.

 (2) In afs_deliver_vl_get_entry_by_name_u(), use the number of server
     records indicated by ->nServers in the UVLDB record returned by the
     VL.GetEntryByNameU RPC call rather than scanning all NMAXNSERVERS
     slots.  Unused slots may contain garbage.

 (3) In afs_alloc_server_list(), don't stop converting a UVLDB record into
     a server list just because we can't look up one of the servers.  Just
     skip that server and go on to the next.  If we can't look up any of
     the servers then we'll fail at the end.

Without this patch, an attempt to view the umich.edu root cell using
something like "ls /afs/umich.edu" on a dynamic root (future patch) mount
or an autocell mount will result in ENOMEDIUM.  The failure is due to kafs
not stopping after nServers'worth of records have been read, but then
trying to access a server with a garbage UUID and getting an error, which
aborts the server list build.

Fixes: d2ddc776a4 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Jonathan Billings <jsbillings@jsbillings.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org
2018-02-06 14:36:54 +00:00

155 lines
3.5 KiB
C

/* AFS fileserver list management.
*
* Copyright (C) 2017 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/slab.h>
#include "internal.h"
void afs_put_serverlist(struct afs_net *net, struct afs_server_list *slist)
{
int i;
if (slist && refcount_dec_and_test(&slist->usage)) {
for (i = 0; i < slist->nr_servers; i++) {
afs_put_cb_interest(net, slist->servers[i].cb_interest);
afs_put_server(net, slist->servers[i].server);
}
kfree(slist);
}
}
/*
* Build a server list from a VLDB record.
*/
struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
struct key *key,
struct afs_vldb_entry *vldb,
u8 type_mask)
{
struct afs_server_list *slist;
struct afs_server *server;
int ret = -ENOMEM, nr_servers = 0, i, j;
for (i = 0; i < vldb->nr_servers; i++)
if (vldb->fs_mask[i] & type_mask)
nr_servers++;
slist = kzalloc(sizeof(struct afs_server_list) +
sizeof(struct afs_server_entry) * nr_servers,
GFP_KERNEL);
if (!slist)
goto error;
refcount_set(&slist->usage, 1);
/* Make sure a records exists for each server in the list. */
for (i = 0; i < vldb->nr_servers; i++) {
if (!(vldb->fs_mask[i] & type_mask))
continue;
server = afs_lookup_server(cell, key, &vldb->fs_server[i]);
if (IS_ERR(server)) {
ret = PTR_ERR(server);
if (ret == -ENOENT ||
ret == -ENOMEDIUM)
continue;
goto error_2;
}
/* Insertion-sort by server pointer */
for (j = 0; j < slist->nr_servers; j++)
if (slist->servers[j].server >= server)
break;
if (j < slist->nr_servers) {
if (slist->servers[j].server == server) {
afs_put_server(cell->net, server);
continue;
}
memmove(slist->servers + j + 1,
slist->servers + j,
(slist->nr_servers - j) * sizeof(struct afs_server_entry));
}
slist->servers[j].server = server;
slist->nr_servers++;
}
if (slist->nr_servers == 0) {
ret = -EDESTADDRREQ;
goto error_2;
}
return slist;
error_2:
afs_put_serverlist(cell->net, slist);
error:
return ERR_PTR(ret);
}
/*
* Copy the annotations from an old server list to its potential replacement.
*/
bool afs_annotate_server_list(struct afs_server_list *new,
struct afs_server_list *old)
{
struct afs_server *cur;
int i, j;
if (old->nr_servers != new->nr_servers)
goto changed;
for (i = 0; i < old->nr_servers; i++)
if (old->servers[i].server != new->servers[i].server)
goto changed;
return false;
changed:
/* Maintain the same current server as before if possible. */
cur = old->servers[old->index].server;
for (j = 0; j < new->nr_servers; j++) {
if (new->servers[j].server == cur) {
new->index = j;
break;
}
}
/* Keep the old callback interest records where possible so that we
* maintain callback interception.
*/
i = 0;
j = 0;
while (i < old->nr_servers && j < new->nr_servers) {
if (new->servers[j].server == old->servers[i].server) {
struct afs_cb_interest *cbi = old->servers[i].cb_interest;
if (cbi) {
new->servers[j].cb_interest = cbi;
refcount_inc(&cbi->usage);
}
i++;
j++;
continue;
}
if (new->servers[j].server < old->servers[i].server) {
j++;
continue;
}
i++;
continue;
}
return true;
}