xref: /openbmc/linux/fs/dlm/plock.c (revision 22246614)
1  /*
2   * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
3   *
4   * This copyrighted material is made available to anyone wishing to use,
5   * modify, copy, or redistribute it subject to the terms and conditions
6   * of the GNU General Public License version 2.
7   */
8  
9  #include <linux/fs.h>
10  #include <linux/miscdevice.h>
11  #include <linux/poll.h>
12  #include <linux/dlm.h>
13  #include <linux/dlm_plock.h>
14  
15  #include "dlm_internal.h"
16  #include "lockspace.h"
17  
18  static spinlock_t ops_lock;
19  static struct list_head send_list;
20  static struct list_head recv_list;
21  static wait_queue_head_t send_wq;
22  static wait_queue_head_t recv_wq;
23  
24  struct plock_op {
25  	struct list_head list;
26  	int done;
27  	struct dlm_plock_info info;
28  };
29  
30  struct plock_xop {
31  	struct plock_op xop;
32  	void *callback;
33  	void *fl;
34  	void *file;
35  	struct file_lock flc;
36  };
37  
38  
39  static inline void set_version(struct dlm_plock_info *info)
40  {
41  	info->version[0] = DLM_PLOCK_VERSION_MAJOR;
42  	info->version[1] = DLM_PLOCK_VERSION_MINOR;
43  	info->version[2] = DLM_PLOCK_VERSION_PATCH;
44  }
45  
46  static int check_version(struct dlm_plock_info *info)
47  {
48  	if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
49  	    (DLM_PLOCK_VERSION_MINOR < info->version[1])) {
50  		log_print("plock device version mismatch: "
51  			  "kernel (%u.%u.%u), user (%u.%u.%u)",
52  			  DLM_PLOCK_VERSION_MAJOR,
53  			  DLM_PLOCK_VERSION_MINOR,
54  			  DLM_PLOCK_VERSION_PATCH,
55  			  info->version[0],
56  			  info->version[1],
57  			  info->version[2]);
58  		return -EINVAL;
59  	}
60  	return 0;
61  }
62  
63  static void send_op(struct plock_op *op)
64  {
65  	set_version(&op->info);
66  	INIT_LIST_HEAD(&op->list);
67  	spin_lock(&ops_lock);
68  	list_add_tail(&op->list, &send_list);
69  	spin_unlock(&ops_lock);
70  	wake_up(&send_wq);
71  }
72  
73  int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
74  		   int cmd, struct file_lock *fl)
75  {
76  	struct dlm_ls *ls;
77  	struct plock_op *op;
78  	struct plock_xop *xop;
79  	int rv;
80  
81  	ls = dlm_find_lockspace_local(lockspace);
82  	if (!ls)
83  		return -EINVAL;
84  
85  	xop = kzalloc(sizeof(*xop), GFP_KERNEL);
86  	if (!xop) {
87  		rv = -ENOMEM;
88  		goto out;
89  	}
90  
91  	op = &xop->xop;
92  	op->info.optype		= DLM_PLOCK_OP_LOCK;
93  	op->info.pid		= fl->fl_pid;
94  	op->info.ex		= (fl->fl_type == F_WRLCK);
95  	op->info.wait		= IS_SETLKW(cmd);
96  	op->info.fsid		= ls->ls_global_id;
97  	op->info.number		= number;
98  	op->info.start		= fl->fl_start;
99  	op->info.end		= fl->fl_end;
100  	if (fl->fl_lmops && fl->fl_lmops->fl_grant) {
101  		/* fl_owner is lockd which doesn't distinguish
102  		   processes on the nfs client */
103  		op->info.owner	= (__u64) fl->fl_pid;
104  		xop->callback	= fl->fl_lmops->fl_grant;
105  		locks_init_lock(&xop->flc);
106  		locks_copy_lock(&xop->flc, fl);
107  		xop->fl		= fl;
108  		xop->file	= file;
109  	} else {
110  		op->info.owner	= (__u64)(long) fl->fl_owner;
111  		xop->callback	= NULL;
112  	}
113  
114  	send_op(op);
115  
116  	if (xop->callback == NULL)
117  		wait_event(recv_wq, (op->done != 0));
118  	else {
119  		rv = -EINPROGRESS;
120  		goto out;
121  	}
122  
123  	spin_lock(&ops_lock);
124  	if (!list_empty(&op->list)) {
125  		log_error(ls, "dlm_posix_lock: op on list %llx",
126  			  (unsigned long long)number);
127  		list_del(&op->list);
128  	}
129  	spin_unlock(&ops_lock);
130  
131  	rv = op->info.rv;
132  
133  	if (!rv) {
134  		if (posix_lock_file_wait(file, fl) < 0)
135  			log_error(ls, "dlm_posix_lock: vfs lock error %llx",
136  				  (unsigned long long)number);
137  	}
138  
139  	kfree(xop);
140  out:
141  	dlm_put_lockspace(ls);
142  	return rv;
143  }
144  EXPORT_SYMBOL_GPL(dlm_posix_lock);
145  
146  /* Returns failure iff a succesful lock operation should be canceled */
147  static int dlm_plock_callback(struct plock_op *op)
148  {
149  	struct file *file;
150  	struct file_lock *fl;
151  	struct file_lock *flc;
152  	int (*notify)(void *, void *, int) = NULL;
153  	struct plock_xop *xop = (struct plock_xop *)op;
154  	int rv = 0;
155  
156  	spin_lock(&ops_lock);
157  	if (!list_empty(&op->list)) {
158  		log_print("dlm_plock_callback: op on list %llx",
159  			  (unsigned long long)op->info.number);
160  		list_del(&op->list);
161  	}
162  	spin_unlock(&ops_lock);
163  
164  	/* check if the following 2 are still valid or make a copy */
165  	file = xop->file;
166  	flc = &xop->flc;
167  	fl = xop->fl;
168  	notify = xop->callback;
169  
170  	if (op->info.rv) {
171  		notify(flc, NULL, op->info.rv);
172  		goto out;
173  	}
174  
175  	/* got fs lock; bookkeep locally as well: */
176  	flc->fl_flags &= ~FL_SLEEP;
177  	if (posix_lock_file(file, flc, NULL)) {
178  		/*
179  		 * This can only happen in the case of kmalloc() failure.
180  		 * The filesystem's own lock is the authoritative lock,
181  		 * so a failure to get the lock locally is not a disaster.
182  		 * As long as the fs cannot reliably cancel locks (especially
183  		 * in a low-memory situation), we're better off ignoring
184  		 * this failure than trying to recover.
185  		 */
186  		log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
187  			  (unsigned long long)op->info.number, file, fl);
188  	}
189  
190  	rv = notify(flc, NULL, 0);
191  	if (rv) {
192  		/* XXX: We need to cancel the fs lock here: */
193  		log_print("dlm_plock_callback: lock granted after lock request "
194  			  "failed; dangling lock!\n");
195  		goto out;
196  	}
197  
198  out:
199  	kfree(xop);
200  	return rv;
201  }
202  
203  int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
204  		     struct file_lock *fl)
205  {
206  	struct dlm_ls *ls;
207  	struct plock_op *op;
208  	int rv;
209  
210  	ls = dlm_find_lockspace_local(lockspace);
211  	if (!ls)
212  		return -EINVAL;
213  
214  	op = kzalloc(sizeof(*op), GFP_KERNEL);
215  	if (!op) {
216  		rv = -ENOMEM;
217  		goto out;
218  	}
219  
220  	if (posix_lock_file_wait(file, fl) < 0)
221  		log_error(ls, "dlm_posix_unlock: vfs unlock error %llx",
222  			  (unsigned long long)number);
223  
224  	op->info.optype		= DLM_PLOCK_OP_UNLOCK;
225  	op->info.pid		= fl->fl_pid;
226  	op->info.fsid		= ls->ls_global_id;
227  	op->info.number		= number;
228  	op->info.start		= fl->fl_start;
229  	op->info.end		= fl->fl_end;
230  	if (fl->fl_lmops && fl->fl_lmops->fl_grant)
231  		op->info.owner	= (__u64) fl->fl_pid;
232  	else
233  		op->info.owner	= (__u64)(long) fl->fl_owner;
234  
235  	send_op(op);
236  	wait_event(recv_wq, (op->done != 0));
237  
238  	spin_lock(&ops_lock);
239  	if (!list_empty(&op->list)) {
240  		log_error(ls, "dlm_posix_unlock: op on list %llx",
241  			  (unsigned long long)number);
242  		list_del(&op->list);
243  	}
244  	spin_unlock(&ops_lock);
245  
246  	rv = op->info.rv;
247  
248  	if (rv == -ENOENT)
249  		rv = 0;
250  
251  	kfree(op);
252  out:
253  	dlm_put_lockspace(ls);
254  	return rv;
255  }
256  EXPORT_SYMBOL_GPL(dlm_posix_unlock);
257  
258  int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
259  		  struct file_lock *fl)
260  {
261  	struct dlm_ls *ls;
262  	struct plock_op *op;
263  	int rv;
264  
265  	ls = dlm_find_lockspace_local(lockspace);
266  	if (!ls)
267  		return -EINVAL;
268  
269  	op = kzalloc(sizeof(*op), GFP_KERNEL);
270  	if (!op) {
271  		rv = -ENOMEM;
272  		goto out;
273  	}
274  
275  	op->info.optype		= DLM_PLOCK_OP_GET;
276  	op->info.pid		= fl->fl_pid;
277  	op->info.ex		= (fl->fl_type == F_WRLCK);
278  	op->info.fsid		= ls->ls_global_id;
279  	op->info.number		= number;
280  	op->info.start		= fl->fl_start;
281  	op->info.end		= fl->fl_end;
282  	if (fl->fl_lmops && fl->fl_lmops->fl_grant)
283  		op->info.owner	= (__u64) fl->fl_pid;
284  	else
285  		op->info.owner	= (__u64)(long) fl->fl_owner;
286  
287  	send_op(op);
288  	wait_event(recv_wq, (op->done != 0));
289  
290  	spin_lock(&ops_lock);
291  	if (!list_empty(&op->list)) {
292  		log_error(ls, "dlm_posix_get: op on list %llx",
293  			  (unsigned long long)number);
294  		list_del(&op->list);
295  	}
296  	spin_unlock(&ops_lock);
297  
298  	/* info.rv from userspace is 1 for conflict, 0 for no-conflict,
299  	   -ENOENT if there are no locks on the file */
300  
301  	rv = op->info.rv;
302  
303  	fl->fl_type = F_UNLCK;
304  	if (rv == -ENOENT)
305  		rv = 0;
306  	else if (rv > 0) {
307  		fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
308  		fl->fl_pid = op->info.pid;
309  		fl->fl_start = op->info.start;
310  		fl->fl_end = op->info.end;
311  		rv = 0;
312  	}
313  
314  	kfree(op);
315  out:
316  	dlm_put_lockspace(ls);
317  	return rv;
318  }
319  EXPORT_SYMBOL_GPL(dlm_posix_get);
320  
321  /* a read copies out one plock request from the send list */
322  static ssize_t dev_read(struct file *file, char __user *u, size_t count,
323  			loff_t *ppos)
324  {
325  	struct dlm_plock_info info;
326  	struct plock_op *op = NULL;
327  
328  	if (count < sizeof(info))
329  		return -EINVAL;
330  
331  	spin_lock(&ops_lock);
332  	if (!list_empty(&send_list)) {
333  		op = list_entry(send_list.next, struct plock_op, list);
334  		list_move(&op->list, &recv_list);
335  		memcpy(&info, &op->info, sizeof(info));
336  	}
337  	spin_unlock(&ops_lock);
338  
339  	if (!op)
340  		return -EAGAIN;
341  
342  	if (copy_to_user(u, &info, sizeof(info)))
343  		return -EFAULT;
344  	return sizeof(info);
345  }
346  
347  /* a write copies in one plock result that should match a plock_op
348     on the recv list */
349  static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
350  			 loff_t *ppos)
351  {
352  	struct dlm_plock_info info;
353  	struct plock_op *op;
354  	int found = 0;
355  
356  	if (count != sizeof(info))
357  		return -EINVAL;
358  
359  	if (copy_from_user(&info, u, sizeof(info)))
360  		return -EFAULT;
361  
362  	if (check_version(&info))
363  		return -EINVAL;
364  
365  	spin_lock(&ops_lock);
366  	list_for_each_entry(op, &recv_list, list) {
367  		if (op->info.fsid == info.fsid && op->info.number == info.number &&
368  		    op->info.owner == info.owner) {
369  			list_del_init(&op->list);
370  			found = 1;
371  			op->done = 1;
372  			memcpy(&op->info, &info, sizeof(info));
373  			break;
374  		}
375  	}
376  	spin_unlock(&ops_lock);
377  
378  	if (found) {
379  		struct plock_xop *xop;
380  		xop = (struct plock_xop *)op;
381  		if (xop->callback)
382  			count = dlm_plock_callback(op);
383  		else
384  			wake_up(&recv_wq);
385  	} else
386  		log_print("dev_write no op %x %llx", info.fsid,
387  			  (unsigned long long)info.number);
388  	return count;
389  }
390  
391  static unsigned int dev_poll(struct file *file, poll_table *wait)
392  {
393  	unsigned int mask = 0;
394  
395  	poll_wait(file, &send_wq, wait);
396  
397  	spin_lock(&ops_lock);
398  	if (!list_empty(&send_list))
399  		mask = POLLIN | POLLRDNORM;
400  	spin_unlock(&ops_lock);
401  
402  	return mask;
403  }
404  
405  static const struct file_operations dev_fops = {
406  	.read    = dev_read,
407  	.write   = dev_write,
408  	.poll    = dev_poll,
409  	.owner   = THIS_MODULE
410  };
411  
412  static struct miscdevice plock_dev_misc = {
413  	.minor = MISC_DYNAMIC_MINOR,
414  	.name = DLM_PLOCK_MISC_NAME,
415  	.fops = &dev_fops
416  };
417  
418  int dlm_plock_init(void)
419  {
420  	int rv;
421  
422  	spin_lock_init(&ops_lock);
423  	INIT_LIST_HEAD(&send_list);
424  	INIT_LIST_HEAD(&recv_list);
425  	init_waitqueue_head(&send_wq);
426  	init_waitqueue_head(&recv_wq);
427  
428  	rv = misc_register(&plock_dev_misc);
429  	if (rv)
430  		log_print("dlm_plock_init: misc_register failed %d", rv);
431  	return rv;
432  }
433  
434  void dlm_plock_exit(void)
435  {
436  	if (misc_deregister(&plock_dev_misc) < 0)
437  		log_print("dlm_plock_exit: misc_deregister failed");
438  }
439  
440