xref: /openbmc/linux/fs/lockd/clntlock.c (revision 87c2ce3b)
1 /*
2  * linux/fs/lockd/clntlock.c
3  *
4  * Lock handling for the client side NLM implementation
5  *
6  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
7  */
8 
9 #include <linux/module.h>
10 #include <linux/types.h>
11 #include <linux/time.h>
12 #include <linux/nfs_fs.h>
13 #include <linux/sunrpc/clnt.h>
14 #include <linux/sunrpc/svc.h>
15 #include <linux/lockd/lockd.h>
16 #include <linux/smp_lock.h>
17 
18 #define NLMDBG_FACILITY		NLMDBG_CLIENT
19 
20 /*
21  * Local function prototypes
22  */
23 static int			reclaimer(void *ptr);
24 
25 /*
26  * The following functions handle blocking and granting from the
27  * client perspective.
28  */
29 
30 /*
31  * This is the representation of a blocked client lock.
32  */
33 struct nlm_wait {
34 	struct list_head	b_list;		/* linked list */
35 	wait_queue_head_t	b_wait;		/* where to wait on */
36 	struct nlm_host *	b_host;
37 	struct file_lock *	b_lock;		/* local file lock */
38 	unsigned short		b_reclaim;	/* got to reclaim lock */
39 	u32			b_status;	/* grant callback status */
40 };
41 
42 static LIST_HEAD(nlm_blocked);
43 
44 /*
45  * Queue up a lock for blocking so that the GRANTED request can see it
46  */
47 int nlmclnt_prepare_block(struct nlm_rqst *req, struct nlm_host *host, struct file_lock *fl)
48 {
49 	struct nlm_wait *block;
50 
51 	BUG_ON(req->a_block != NULL);
52 	block = kmalloc(sizeof(*block), GFP_KERNEL);
53 	if (block == NULL)
54 		return -ENOMEM;
55 	block->b_host = host;
56 	block->b_lock = fl;
57 	init_waitqueue_head(&block->b_wait);
58 	block->b_status = NLM_LCK_BLOCKED;
59 
60 	list_add(&block->b_list, &nlm_blocked);
61 	req->a_block = block;
62 
63 	return 0;
64 }
65 
66 void nlmclnt_finish_block(struct nlm_rqst *req)
67 {
68 	struct nlm_wait *block = req->a_block;
69 
70 	if (block == NULL)
71 		return;
72 	req->a_block = NULL;
73 	list_del(&block->b_list);
74 	kfree(block);
75 }
76 
77 /*
78  * Block on a lock
79  */
80 long nlmclnt_block(struct nlm_rqst *req, long timeout)
81 {
82 	struct nlm_wait	*block = req->a_block;
83 	long ret;
84 
85 	/* A borken server might ask us to block even if we didn't
86 	 * request it. Just say no!
87 	 */
88 	if (!req->a_args.block)
89 		return -EAGAIN;
90 
91 	/* Go to sleep waiting for GRANT callback. Some servers seem
92 	 * to lose callbacks, however, so we're going to poll from
93 	 * time to time just to make sure.
94 	 *
95 	 * For now, the retry frequency is pretty high; normally
96 	 * a 1 minute timeout would do. See the comment before
97 	 * nlmclnt_lock for an explanation.
98 	 */
99 	ret = wait_event_interruptible_timeout(block->b_wait,
100 			block->b_status != NLM_LCK_BLOCKED,
101 			timeout);
102 
103 	if (block->b_status != NLM_LCK_BLOCKED) {
104 		req->a_res.status = block->b_status;
105 		block->b_status = NLM_LCK_BLOCKED;
106 	}
107 
108 	return ret;
109 }
110 
111 /*
112  * The server lockd has called us back to tell us the lock was granted
113  */
114 u32
115 nlmclnt_grant(struct nlm_lock *lock)
116 {
117 	struct nlm_wait	*block;
118 	u32 res = nlm_lck_denied;
119 
120 	/*
121 	 * Look up blocked request based on arguments.
122 	 * Warning: must not use cookie to match it!
123 	 */
124 	list_for_each_entry(block, &nlm_blocked, b_list) {
125 		if (nlm_compare_locks(block->b_lock, &lock->fl)) {
126 			/* Alright, we found a lock. Set the return status
127 			 * and wake up the caller
128 			 */
129 			block->b_status = NLM_LCK_GRANTED;
130 			wake_up(&block->b_wait);
131 			res = nlm_granted;
132 		}
133 	}
134 	return res;
135 }
136 
137 /*
138  * The following procedures deal with the recovery of locks after a
139  * server crash.
140  */
141 
142 /*
143  * Mark the locks for reclaiming.
144  * FIXME: In 2.5 we don't want to iterate through any global file_lock_list.
145  *        Maintain NLM lock reclaiming lists in the nlm_host instead.
146  */
147 static
148 void nlmclnt_mark_reclaim(struct nlm_host *host)
149 {
150 	struct file_lock *fl;
151 	struct inode *inode;
152 	struct list_head *tmp;
153 
154 	list_for_each(tmp, &file_lock_list) {
155 		fl = list_entry(tmp, struct file_lock, fl_link);
156 
157 		inode = fl->fl_file->f_dentry->d_inode;
158 		if (inode->i_sb->s_magic != NFS_SUPER_MAGIC)
159 			continue;
160 		if (fl->fl_u.nfs_fl.owner == NULL)
161 			continue;
162 		if (fl->fl_u.nfs_fl.owner->host != host)
163 			continue;
164 		if (!(fl->fl_u.nfs_fl.flags & NFS_LCK_GRANTED))
165 			continue;
166 		fl->fl_u.nfs_fl.flags |= NFS_LCK_RECLAIM;
167 	}
168 }
169 
170 /*
171  * Someone has sent us an SM_NOTIFY. Ensure we bind to the new port number,
172  * that we mark locks for reclaiming, and that we bump the pseudo NSM state.
173  */
174 static inline
175 void nlmclnt_prepare_reclaim(struct nlm_host *host, u32 newstate)
176 {
177 	host->h_monitored = 0;
178 	host->h_nsmstate = newstate;
179 	host->h_state++;
180 	host->h_nextrebind = 0;
181 	nlm_rebind_host(host);
182 	nlmclnt_mark_reclaim(host);
183 	dprintk("NLM: reclaiming locks for host %s", host->h_name);
184 }
185 
186 /*
187  * Reclaim all locks on server host. We do this by spawning a separate
188  * reclaimer thread.
189  */
190 void
191 nlmclnt_recovery(struct nlm_host *host, u32 newstate)
192 {
193 	if (host->h_reclaiming++) {
194 		if (host->h_nsmstate == newstate)
195 			return;
196 		nlmclnt_prepare_reclaim(host, newstate);
197 	} else {
198 		nlmclnt_prepare_reclaim(host, newstate);
199 		nlm_get_host(host);
200 		__module_get(THIS_MODULE);
201 		if (kernel_thread(reclaimer, host, CLONE_KERNEL) < 0)
202 			module_put(THIS_MODULE);
203 	}
204 }
205 
206 static int
207 reclaimer(void *ptr)
208 {
209 	struct nlm_host	  *host = (struct nlm_host *) ptr;
210 	struct nlm_wait	  *block;
211 	struct list_head *tmp;
212 	struct file_lock *fl;
213 	struct inode *inode;
214 
215 	daemonize("%s-reclaim", host->h_name);
216 	allow_signal(SIGKILL);
217 
218 	/* This one ensures that our parent doesn't terminate while the
219 	 * reclaim is in progress */
220 	lock_kernel();
221 	lockd_up();
222 
223 	/* First, reclaim all locks that have been marked. */
224 restart:
225 	list_for_each(tmp, &file_lock_list) {
226 		fl = list_entry(tmp, struct file_lock, fl_link);
227 
228 		inode = fl->fl_file->f_dentry->d_inode;
229 		if (inode->i_sb->s_magic != NFS_SUPER_MAGIC)
230 			continue;
231 		if (fl->fl_u.nfs_fl.owner == NULL)
232 			continue;
233 		if (fl->fl_u.nfs_fl.owner->host != host)
234 			continue;
235 		if (!(fl->fl_u.nfs_fl.flags & NFS_LCK_RECLAIM))
236 			continue;
237 
238 		fl->fl_u.nfs_fl.flags &= ~NFS_LCK_RECLAIM;
239 		nlmclnt_reclaim(host, fl);
240 		if (signalled())
241 			break;
242 		goto restart;
243 	}
244 
245 	host->h_reclaiming = 0;
246 
247 	/* Now, wake up all processes that sleep on a blocked lock */
248 	list_for_each_entry(block, &nlm_blocked, b_list) {
249 		if (block->b_host == host) {
250 			block->b_status = NLM_LCK_DENIED_GRACE_PERIOD;
251 			wake_up(&block->b_wait);
252 		}
253 	}
254 
255 	/* Release host handle after use */
256 	nlm_release_host(host);
257 	lockd_down();
258 	unlock_kernel();
259 	module_put_and_exit(0);
260 }
261