1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * linux/fs/lockd/clntlock.c
4  *
5  * Lock handling for the client side NLM implementation
6  *
7  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
8  */
9 
10 #include <linux/module.h>
11 #include <linux/types.h>
12 #include <linux/slab.h>
13 #include <linux/time.h>
14 #include <linux/nfs_fs.h>
15 #include <linux/sunrpc/addr.h>
16 #include <linux/sunrpc/svc.h>
17 #include <linux/lockd/lockd.h>
18 #include <linux/kthread.h>
19 
20 #define NLMDBG_FACILITY		NLMDBG_CLIENT
21 
22 /*
23  * Local function prototypes
24  */
25 static int			reclaimer(void *ptr);
26 
27 /*
28  * The following functions handle blocking and granting from the
29  * client perspective.
30  */
31 
32 /*
33  * This is the representation of a blocked client lock.
34  */
35 struct nlm_wait {
36 	struct list_head	b_list;		/* linked list */
37 	wait_queue_head_t	b_wait;		/* where to wait on */
38 	struct nlm_host *	b_host;
39 	struct file_lock *	b_lock;		/* local file lock */
40 	unsigned short		b_reclaim;	/* got to reclaim lock */
41 	__be32			b_status;	/* grant callback status */
42 };
43 
44 static LIST_HEAD(nlm_blocked);
45 static DEFINE_SPINLOCK(nlm_blocked_lock);
46 
47 /**
48  * nlmclnt_init - Set up per-NFS mount point lockd data structures
49  * @nlm_init: pointer to arguments structure
50  *
51  * Returns pointer to an appropriate nlm_host struct,
52  * or an ERR_PTR value.
53  */
nlmclnt_init(const struct nlmclnt_initdata * nlm_init)54 struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init)
55 {
56 	struct nlm_host *host;
57 	u32 nlm_version = (nlm_init->nfs_version == 2) ? 1 : 4;
58 	int status;
59 
60 	status = lockd_up(nlm_init->net, nlm_init->cred);
61 	if (status < 0)
62 		return ERR_PTR(status);
63 
64 	host = nlmclnt_lookup_host(nlm_init->address, nlm_init->addrlen,
65 				   nlm_init->protocol, nlm_version,
66 				   nlm_init->hostname, nlm_init->noresvport,
67 				   nlm_init->net, nlm_init->cred);
68 	if (host == NULL)
69 		goto out_nohost;
70 	if (host->h_rpcclnt == NULL && nlm_bind_host(host) == NULL)
71 		goto out_nobind;
72 
73 	host->h_nlmclnt_ops = nlm_init->nlmclnt_ops;
74 	return host;
75 out_nobind:
76 	nlmclnt_release_host(host);
77 out_nohost:
78 	lockd_down(nlm_init->net);
79 	return ERR_PTR(-ENOLCK);
80 }
81 EXPORT_SYMBOL_GPL(nlmclnt_init);
82 
83 /**
84  * nlmclnt_done - Release resources allocated by nlmclnt_init()
85  * @host: nlm_host structure reserved by nlmclnt_init()
86  *
87  */
nlmclnt_done(struct nlm_host * host)88 void nlmclnt_done(struct nlm_host *host)
89 {
90 	struct net *net = host->net;
91 
92 	nlmclnt_release_host(host);
93 	lockd_down(net);
94 }
95 EXPORT_SYMBOL_GPL(nlmclnt_done);
96 
97 /*
98  * Queue up a lock for blocking so that the GRANTED request can see it
99  */
nlmclnt_prepare_block(struct nlm_host * host,struct file_lock * fl)100 struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)
101 {
102 	struct nlm_wait *block;
103 
104 	block = kmalloc(sizeof(*block), GFP_KERNEL);
105 	if (block != NULL) {
106 		block->b_host = host;
107 		block->b_lock = fl;
108 		init_waitqueue_head(&block->b_wait);
109 		block->b_status = nlm_lck_blocked;
110 
111 		spin_lock(&nlm_blocked_lock);
112 		list_add(&block->b_list, &nlm_blocked);
113 		spin_unlock(&nlm_blocked_lock);
114 	}
115 	return block;
116 }
117 
nlmclnt_finish_block(struct nlm_wait * block)118 void nlmclnt_finish_block(struct nlm_wait *block)
119 {
120 	if (block == NULL)
121 		return;
122 	spin_lock(&nlm_blocked_lock);
123 	list_del(&block->b_list);
124 	spin_unlock(&nlm_blocked_lock);
125 	kfree(block);
126 }
127 
128 /*
129  * Block on a lock
130  */
nlmclnt_block(struct nlm_wait * block,struct nlm_rqst * req,long timeout)131 int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)
132 {
133 	long ret;
134 
135 	/* A borken server might ask us to block even if we didn't
136 	 * request it. Just say no!
137 	 */
138 	if (block == NULL)
139 		return -EAGAIN;
140 
141 	/* Go to sleep waiting for GRANT callback. Some servers seem
142 	 * to lose callbacks, however, so we're going to poll from
143 	 * time to time just to make sure.
144 	 *
145 	 * For now, the retry frequency is pretty high; normally
146 	 * a 1 minute timeout would do. See the comment before
147 	 * nlmclnt_lock for an explanation.
148 	 */
149 	ret = wait_event_interruptible_timeout(block->b_wait,
150 			block->b_status != nlm_lck_blocked,
151 			timeout);
152 	if (ret < 0)
153 		return -ERESTARTSYS;
154 	/* Reset the lock status after a server reboot so we resend */
155 	if (block->b_status == nlm_lck_denied_grace_period)
156 		block->b_status = nlm_lck_blocked;
157 	req->a_res.status = block->b_status;
158 	return 0;
159 }
160 
161 /*
162  * The server lockd has called us back to tell us the lock was granted
163  */
nlmclnt_grant(const struct sockaddr * addr,const struct nlm_lock * lock)164 __be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
165 {
166 	const struct file_lock *fl = &lock->fl;
167 	const struct nfs_fh *fh = &lock->fh;
168 	struct nlm_wait	*block;
169 	__be32 res = nlm_lck_denied;
170 
171 	/*
172 	 * Look up blocked request based on arguments.
173 	 * Warning: must not use cookie to match it!
174 	 */
175 	spin_lock(&nlm_blocked_lock);
176 	list_for_each_entry(block, &nlm_blocked, b_list) {
177 		struct file_lock *fl_blocked = block->b_lock;
178 
179 		if (fl_blocked->fl_start != fl->fl_start)
180 			continue;
181 		if (fl_blocked->fl_end != fl->fl_end)
182 			continue;
183 		/*
184 		 * Careful! The NLM server will return the 32-bit "pid" that
185 		 * we put on the wire: in this case the lockowner "pid".
186 		 */
187 		if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)
188 			continue;
189 		if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))
190 			continue;
191 		if (nfs_compare_fh(NFS_FH(locks_inode(fl_blocked->fl_file)), fh) != 0)
192 			continue;
193 		/* Alright, we found a lock. Set the return status
194 		 * and wake up the caller
195 		 */
196 		block->b_status = nlm_granted;
197 		wake_up(&block->b_wait);
198 		res = nlm_granted;
199 	}
200 	spin_unlock(&nlm_blocked_lock);
201 	return res;
202 }
203 
204 /*
205  * The following procedures deal with the recovery of locks after a
206  * server crash.
207  */
208 
209 /*
210  * Reclaim all locks on server host. We do this by spawning a separate
211  * reclaimer thread.
212  */
213 void
nlmclnt_recovery(struct nlm_host * host)214 nlmclnt_recovery(struct nlm_host *host)
215 {
216 	struct task_struct *task;
217 
218 	if (!host->h_reclaiming++) {
219 		nlm_get_host(host);
220 		task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
221 		if (IS_ERR(task))
222 			printk(KERN_ERR "lockd: unable to spawn reclaimer "
223 				"thread. Locks for %s won't be reclaimed! "
224 				"(%ld)\n", host->h_name, PTR_ERR(task));
225 	}
226 }
227 
228 static int
reclaimer(void * ptr)229 reclaimer(void *ptr)
230 {
231 	struct nlm_host	  *host = (struct nlm_host *) ptr;
232 	struct nlm_wait	  *block;
233 	struct nlm_rqst   *req;
234 	struct file_lock *fl, *next;
235 	u32 nsmstate;
236 	struct net *net = host->net;
237 
238 	req = kmalloc(sizeof(*req), GFP_KERNEL);
239 	if (!req)
240 		return 0;
241 
242 	allow_signal(SIGKILL);
243 
244 	down_write(&host->h_rwsem);
245 	lockd_up(net, NULL);	/* note: this cannot fail as lockd is already running */
246 
247 	dprintk("lockd: reclaiming locks for host %s\n", host->h_name);
248 
249 restart:
250 	nsmstate = host->h_nsmstate;
251 
252 	/* Force a portmap getport - the peer's lockd will
253 	 * most likely end up on a different port.
254 	 */
255 	host->h_nextrebind = jiffies;
256 	nlm_rebind_host(host);
257 
258 	/* First, reclaim all locks that have been granted. */
259 	list_splice_init(&host->h_granted, &host->h_reclaim);
260 	list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
261 		list_del_init(&fl->fl_u.nfs_fl.list);
262 
263 		/*
264 		 * sending this thread a SIGKILL will result in any unreclaimed
265 		 * locks being removed from the h_granted list. This means that
266 		 * the kernel will not attempt to reclaim them again if a new
267 		 * reclaimer thread is spawned for this host.
268 		 */
269 		if (signalled())
270 			continue;
271 		if (nlmclnt_reclaim(host, fl, req) != 0)
272 			continue;
273 		list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
274 		if (host->h_nsmstate != nsmstate) {
275 			/* Argh! The server rebooted again! */
276 			goto restart;
277 		}
278 	}
279 
280 	host->h_reclaiming = 0;
281 	up_write(&host->h_rwsem);
282 	dprintk("NLM: done reclaiming locks for host %s\n", host->h_name);
283 
284 	/* Now, wake up all processes that sleep on a blocked lock */
285 	spin_lock(&nlm_blocked_lock);
286 	list_for_each_entry(block, &nlm_blocked, b_list) {
287 		if (block->b_host == host) {
288 			block->b_status = nlm_lck_denied_grace_period;
289 			wake_up(&block->b_wait);
290 		}
291 	}
292 	spin_unlock(&nlm_blocked_lock);
293 
294 	/* Release host handle after use */
295 	nlmclnt_release_host(host);
296 	lockd_down(net);
297 	kfree(req);
298 	return 0;
299 }
300