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alistair23-linux/fs/afs/main.c
David Howells 5481fc6eb8 afs: Fix hang on rmmod due to outstanding timer 
The fileserver probe timer, net->fs_probe_timer, isn't cancelled when
the kafs module is being removed and so the count it holds on
net->servers_outstanding doesn't get dropped..

This causes rmmod to wait forever.  The hung process shows a stack like:

	afs_purge_servers+0x1b5/0x23c [kafs]
	afs_net_exit+0x44/0x6e [kafs]
	ops_exit_list+0x72/0x93
	unregister_pernet_operations+0x14c/0x1ba
	unregister_pernet_subsys+0x1d/0x2a
	afs_exit+0x29/0x6f [kafs]
	__do_sys_delete_module.isra.0+0x1a2/0x24b
	do_syscall_64+0x51/0x95
	entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix this by:

 (1) Attempting to cancel the probe timer and, if successful, drop the
     count that the timer was holding.

 (2) Make the timer function just drop the count and not schedule the
     prober if the afs portion of net namespace is being destroyed.

Also, whilst we're at it, make the following changes:

 (3) Initialise net->servers_outstanding to 1 and decrement it before
     waiting on it so that it doesn't generate wake up events by being
     decremented to 0 until we're cleaning up.

 (4) Switch the atomic_dec() on ->servers_outstanding for ->fs_timer in
     afs_purge_servers() to use the helper function for that.

Fixes: f6cbb368bc ("afs: Actively poll fileservers to maintain NAT or firewall openings")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-20 12:01:58 -07:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS client file system
*
* Copyright (C) 2002,5 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/random.h>
#include <linux/proc_fs.h>
#define CREATE_TRACE_POINTS
#include "internal.h"
MODULE_DESCRIPTION("AFS Client File System");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");
unsigned afs_debug;
module_param_named(debug, afs_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(debug, "AFS debugging mask");
static char *rootcell;
module_param(rootcell, charp, 0);
MODULE_PARM_DESC(rootcell, "root AFS cell name and VL server IP addr list");
struct workqueue_struct *afs_wq;
static struct proc_dir_entry *afs_proc_symlink;
#if defined(CONFIG_ALPHA)
const char afs_init_sysname[] = "alpha_linux26";
#elif defined(CONFIG_X86_64)
const char afs_init_sysname[] = "amd64_linux26";
#elif defined(CONFIG_ARM)
const char afs_init_sysname[] = "arm_linux26";
#elif defined(CONFIG_ARM64)
const char afs_init_sysname[] = "aarch64_linux26";
#elif defined(CONFIG_X86_32)
const char afs_init_sysname[] = "i386_linux26";
#elif defined(CONFIG_IA64)
const char afs_init_sysname[] = "ia64_linux26";
#elif defined(CONFIG_PPC64)
const char afs_init_sysname[] = "ppc64_linux26";
#elif defined(CONFIG_PPC32)
const char afs_init_sysname[] = "ppc_linux26";
#elif defined(CONFIG_S390)
#ifdef CONFIG_64BIT
const char afs_init_sysname[] = "s390x_linux26";
#else
const char afs_init_sysname[] = "s390_linux26";
#endif
#elif defined(CONFIG_SPARC64)
const char afs_init_sysname[] = "sparc64_linux26";
#elif defined(CONFIG_SPARC32)
const char afs_init_sysname[] = "sparc_linux26";
#else
const char afs_init_sysname[] = "unknown_linux26";
#endif
/*
* Initialise an AFS network namespace record.
*/
static int __net_init afs_net_init(struct net *net_ns)
{
struct afs_sysnames *sysnames;
struct afs_net *net = afs_net(net_ns);
int ret;
net->net = net_ns;
net->live = true;
generate_random_uuid((unsigned char *)&net->uuid);
INIT_WORK(&net->charge_preallocation_work, afs_charge_preallocation);
mutex_init(&net->socket_mutex);
net->cells = RB_ROOT;
seqlock_init(&net->cells_lock);
INIT_WORK(&net->cells_manager, afs_manage_cells);
timer_setup(&net->cells_timer, afs_cells_timer, 0);
mutex_init(&net->cells_alias_lock);
mutex_init(&net->proc_cells_lock);
INIT_HLIST_HEAD(&net->proc_cells);
seqlock_init(&net->fs_lock);
net->fs_servers = RB_ROOT;
INIT_LIST_HEAD(&net->fs_probe_fast);
INIT_LIST_HEAD(&net->fs_probe_slow);
INIT_HLIST_HEAD(&net->fs_proc);
INIT_HLIST_HEAD(&net->fs_addresses4);
INIT_HLIST_HEAD(&net->fs_addresses6);
seqlock_init(&net->fs_addr_lock);
INIT_WORK(&net->fs_manager, afs_manage_servers);
timer_setup(&net->fs_timer, afs_servers_timer, 0);
INIT_WORK(&net->fs_prober, afs_fs_probe_dispatcher);
timer_setup(&net->fs_probe_timer, afs_fs_probe_timer, 0);
atomic_set(&net->servers_outstanding, 1);
ret = -ENOMEM;
sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);
if (!sysnames)
goto error_sysnames;
sysnames->subs[0] = (char *)&afs_init_sysname;
sysnames->nr = 1;
refcount_set(&sysnames->usage, 1);
net->sysnames = sysnames;
rwlock_init(&net->sysnames_lock);
/* Register the /proc stuff */
ret = afs_proc_init(net);
if (ret < 0)
goto error_proc;
/* Initialise the cell DB */
ret = afs_cell_init(net, rootcell);
if (ret < 0)
goto error_cell_init;
/* Create the RxRPC transport */
ret = afs_open_socket(net);
if (ret < 0)
goto error_open_socket;
return 0;
error_open_socket:
net->live = false;
afs_fs_probe_cleanup(net);
afs_cell_purge(net);
afs_purge_servers(net);
error_cell_init:
net->live = false;
afs_proc_cleanup(net);
error_proc:
afs_put_sysnames(net->sysnames);
error_sysnames:
net->live = false;
return ret;
}
/*
* Clean up and destroy an AFS network namespace record.
*/
static void __net_exit afs_net_exit(struct net *net_ns)
{
struct afs_net *net = afs_net(net_ns);
net->live = false;
afs_fs_probe_cleanup(net);
afs_cell_purge(net);
afs_purge_servers(net);
afs_close_socket(net);
afs_proc_cleanup(net);
afs_put_sysnames(net->sysnames);
}
static struct pernet_operations afs_net_ops = {
.init = afs_net_init,
.exit = afs_net_exit,
.id = &afs_net_id,
.size = sizeof(struct afs_net),
};
/*
* initialise the AFS client FS module
*/
static int __init afs_init(void)
{
int ret = -ENOMEM;
printk(KERN_INFO "kAFS: Red Hat AFS client v0.1 registering.\n");
afs_wq = alloc_workqueue("afs", 0, 0);
if (!afs_wq)
goto error_afs_wq;
afs_async_calls = alloc_workqueue("kafsd", WQ_MEM_RECLAIM, 0);
if (!afs_async_calls)
goto error_async;
afs_lock_manager = alloc_workqueue("kafs_lockd", WQ_MEM_RECLAIM, 0);
if (!afs_lock_manager)
goto error_lockmgr;
#ifdef CONFIG_AFS_FSCACHE
/* we want to be able to cache */
ret = fscache_register_netfs(&afs_cache_netfs);
if (ret < 0)
goto error_cache;
#endif
ret = register_pernet_subsys(&afs_net_ops);
if (ret < 0)
goto error_net;
/* register the filesystems */
ret = afs_fs_init();
if (ret < 0)
goto error_fs;
afs_proc_symlink = proc_symlink("fs/afs", NULL, "../self/net/afs");
if (IS_ERR(afs_proc_symlink)) {
ret = PTR_ERR(afs_proc_symlink);
goto error_proc;
}
return ret;
error_proc:
afs_fs_exit();
error_fs:
unregister_pernet_subsys(&afs_net_ops);
error_net:
#ifdef CONFIG_AFS_FSCACHE
fscache_unregister_netfs(&afs_cache_netfs);
error_cache:
#endif
destroy_workqueue(afs_lock_manager);
error_lockmgr:
destroy_workqueue(afs_async_calls);
error_async:
destroy_workqueue(afs_wq);
error_afs_wq:
rcu_barrier();
printk(KERN_ERR "kAFS: failed to register: %d\n", ret);
return ret;
}
/* XXX late_initcall is kludgy, but the only alternative seems to create
* a transport upon the first mount, which is worse. Or is it?
*/
late_initcall(afs_init); /* must be called after net/ to create socket */
/*
* clean up on module removal
*/
static void __exit afs_exit(void)
{
printk(KERN_INFO "kAFS: Red Hat AFS client v0.1 unregistering.\n");
proc_remove(afs_proc_symlink);
afs_fs_exit();
unregister_pernet_subsys(&afs_net_ops);
#ifdef CONFIG_AFS_FSCACHE
fscache_unregister_netfs(&afs_cache_netfs);
#endif
destroy_workqueue(afs_lock_manager);
destroy_workqueue(afs_async_calls);
destroy_workqueue(afs_wq);
afs_clean_up_permit_cache();
rcu_barrier();
}
module_exit(afs_exit);
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