sparse pointer use of zero as null
[linux-3.10.git] / fs / autofs4 / waitq.c
1 /* -*- c -*- --------------------------------------------------------------- *
2  *
3  * linux/fs/autofs/waitq.c
4  *
5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
6  *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
7  *
8  * This file is part of the Linux kernel and is made available under
9  * the terms of the GNU General Public License, version 2, or at your
10  * option, any later version, incorporated herein by reference.
11  *
12  * ------------------------------------------------------------------------- */
13
14 #include <linux/slab.h>
15 #include <linux/time.h>
16 #include <linux/signal.h>
17 #include <linux/file.h>
18 #include "autofs_i.h"
19
20 /* We make this a static variable rather than a part of the superblock; it
21    is better if we don't reassign numbers easily even across filesystems */
22 static autofs_wqt_t autofs4_next_wait_queue = 1;
23
24 /* These are the signals we allow interrupting a pending mount */
25 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
26
27 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
28 {
29         struct autofs_wait_queue *wq, *nwq;
30
31         DPRINTK("entering catatonic mode");
32
33         sbi->catatonic = 1;
34         wq = sbi->queues;
35         sbi->queues = NULL;     /* Erase all wait queues */
36         while (wq) {
37                 nwq = wq->next;
38                 wq->status = -ENOENT; /* Magic is gone - report failure */
39                 kfree(wq->name);
40                 wq->name = NULL;
41                 wake_up_interruptible(&wq->queue);
42                 wq = nwq;
43         }
44         fput(sbi->pipe);        /* Close the pipe */
45         sbi->pipe = NULL;
46 }
47
48 static int autofs4_write(struct file *file, const void *addr, int bytes)
49 {
50         unsigned long sigpipe, flags;
51         mm_segment_t fs;
52         const char *data = (const char *)addr;
53         ssize_t wr = 0;
54
55         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
56
57         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
58
59         /* Save pointer to user space and point back to kernel space */
60         fs = get_fs();
61         set_fs(KERNEL_DS);
62
63         while (bytes &&
64                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
65                 data += wr;
66                 bytes -= wr;
67         }
68
69         set_fs(fs);
70
71         /* Keep the currently executing process from receiving a
72            SIGPIPE unless it was already supposed to get one */
73         if (wr == -EPIPE && !sigpipe) {
74                 spin_lock_irqsave(&current->sighand->siglock, flags);
75                 sigdelset(&current->pending.signal, SIGPIPE);
76                 recalc_sigpending();
77                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
78         }
79
80         return (bytes > 0);
81 }
82         
83 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
84                                  struct autofs_wait_queue *wq,
85                                  int type)
86 {
87         union {
88                 struct autofs_packet_hdr hdr;
89                 union autofs_packet_union v4_pkt;
90                 union autofs_v5_packet_union v5_pkt;
91         } pkt;
92         size_t pktsz;
93
94         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
95                 wq->wait_queue_token, wq->len, wq->name, type);
96
97         memset(&pkt,0,sizeof pkt); /* For security reasons */
98
99         pkt.hdr.proto_version = sbi->version;
100         pkt.hdr.type = type;
101         switch (type) {
102         /* Kernel protocol v4 missing and expire packets */
103         case autofs_ptype_missing:
104         {
105                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
106
107                 pktsz = sizeof(*mp);
108
109                 mp->wait_queue_token = wq->wait_queue_token;
110                 mp->len = wq->len;
111                 memcpy(mp->name, wq->name, wq->len);
112                 mp->name[wq->len] = '\0';
113                 break;
114         }
115         case autofs_ptype_expire_multi:
116         {
117                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
118
119                 pktsz = sizeof(*ep);
120
121                 ep->wait_queue_token = wq->wait_queue_token;
122                 ep->len = wq->len;
123                 memcpy(ep->name, wq->name, wq->len);
124                 ep->name[wq->len] = '\0';
125                 break;
126         }
127         /*
128          * Kernel protocol v5 packet for handling indirect and direct
129          * mount missing and expire requests
130          */
131         case autofs_ptype_missing_indirect:
132         case autofs_ptype_expire_indirect:
133         case autofs_ptype_missing_direct:
134         case autofs_ptype_expire_direct:
135         {
136                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
137
138                 pktsz = sizeof(*packet);
139
140                 packet->wait_queue_token = wq->wait_queue_token;
141                 packet->len = wq->len;
142                 memcpy(packet->name, wq->name, wq->len);
143                 packet->name[wq->len] = '\0';
144                 packet->dev = wq->dev;
145                 packet->ino = wq->ino;
146                 packet->uid = wq->uid;
147                 packet->gid = wq->gid;
148                 packet->pid = wq->pid;
149                 packet->tgid = wq->tgid;
150                 break;
151         }
152         default:
153                 printk("autofs4_notify_daemon: bad type %d!\n", type);
154                 return;
155         }
156
157         if (autofs4_write(sbi->pipe, &pkt, pktsz))
158                 autofs4_catatonic_mode(sbi);
159 }
160
161 static int autofs4_getpath(struct autofs_sb_info *sbi,
162                            struct dentry *dentry, char **name)
163 {
164         struct dentry *root = sbi->sb->s_root;
165         struct dentry *tmp;
166         char *buf = *name;
167         char *p;
168         int len = 0;
169
170         spin_lock(&dcache_lock);
171         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
172                 len += tmp->d_name.len + 1;
173
174         if (--len > NAME_MAX) {
175                 spin_unlock(&dcache_lock);
176                 return 0;
177         }
178
179         *(buf + len) = '\0';
180         p = buf + len - dentry->d_name.len;
181         strncpy(p, dentry->d_name.name, dentry->d_name.len);
182
183         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
184                 *(--p) = '/';
185                 p -= tmp->d_name.len;
186                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
187         }
188         spin_unlock(&dcache_lock);
189
190         return len;
191 }
192
193 static struct autofs_wait_queue *
194 autofs4_find_wait(struct autofs_sb_info *sbi,
195                   char *name, unsigned int hash, unsigned int len)
196 {
197         struct autofs_wait_queue *wq;
198
199         for (wq = sbi->queues; wq; wq = wq->next) {
200                 if (wq->hash == hash &&
201                     wq->len == len &&
202                     wq->name && !memcmp(wq->name, name, len))
203                         break;
204         }
205         return wq;
206 }
207
208 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
209                 enum autofs_notify notify)
210 {
211         struct autofs_info *ino;
212         struct autofs_wait_queue *wq;
213         char *name;
214         unsigned int len = 0;
215         unsigned int hash = 0;
216         int status, type;
217
218         /* In catatonic mode, we don't wait for nobody */
219         if (sbi->catatonic)
220                 return -ENOENT;
221         
222         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
223         if (!name)
224                 return -ENOMEM;
225
226         /* If this is a direct mount request create a dummy name */
227         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
228                 len = sprintf(name, "%p", dentry);
229         else {
230                 len = autofs4_getpath(sbi, dentry, &name);
231                 if (!len) {
232                         kfree(name);
233                         return -ENOENT;
234                 }
235         }
236         hash = full_name_hash(name, len);
237
238         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
239                 kfree(name);
240                 return -EINTR;
241         }
242
243         wq = autofs4_find_wait(sbi, name, hash, len);
244         ino = autofs4_dentry_ino(dentry);
245         if (!wq && ino && notify == NFY_NONE) {
246                 /*
247                  * Either we've betean the pending expire to post it's
248                  * wait or it finished while we waited on the mutex.
249                  * So we need to wait till either, the wait appears
250                  * or the expire finishes.
251                  */
252
253                 while (ino->flags & AUTOFS_INF_EXPIRING) {
254                         mutex_unlock(&sbi->wq_mutex);
255                         schedule_timeout_interruptible(HZ/10);
256                         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
257                                 kfree(name);
258                                 return -EINTR;
259                         }
260                         wq = autofs4_find_wait(sbi, name, hash, len);
261                         if (wq)
262                                 break;
263                 }
264
265                 /*
266                  * Not ideal but the status has already gone. Of the two
267                  * cases where we wait on NFY_NONE neither depend on the
268                  * return status of the wait.
269                  */
270                 if (!wq) {
271                         kfree(name);
272                         mutex_unlock(&sbi->wq_mutex);
273                         return 0;
274                 }
275         }
276
277         if (!wq) {
278                 /* Create a new wait queue */
279                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
280                 if (!wq) {
281                         kfree(name);
282                         mutex_unlock(&sbi->wq_mutex);
283                         return -ENOMEM;
284                 }
285
286                 wq->wait_queue_token = autofs4_next_wait_queue;
287                 if (++autofs4_next_wait_queue == 0)
288                         autofs4_next_wait_queue = 1;
289                 wq->next = sbi->queues;
290                 sbi->queues = wq;
291                 init_waitqueue_head(&wq->queue);
292                 wq->hash = hash;
293                 wq->name = name;
294                 wq->len = len;
295                 wq->dev = autofs4_get_dev(sbi);
296                 wq->ino = autofs4_get_ino(sbi);
297                 wq->uid = current->uid;
298                 wq->gid = current->gid;
299                 wq->pid = current->pid;
300                 wq->tgid = current->tgid;
301                 wq->status = -EINTR; /* Status return if interrupted */
302                 atomic_set(&wq->wait_ctr, 2);
303                 mutex_unlock(&sbi->wq_mutex);
304
305                 if (sbi->version < 5) {
306                         if (notify == NFY_MOUNT)
307                                 type = autofs_ptype_missing;
308                         else
309                                 type = autofs_ptype_expire_multi;
310                 } else {
311                         if (notify == NFY_MOUNT)
312                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
313                                         autofs_ptype_missing_direct :
314                                          autofs_ptype_missing_indirect;
315                         else
316                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
317                                         autofs_ptype_expire_direct :
318                                         autofs_ptype_expire_indirect;
319                 }
320
321                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
322                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
323
324                 /* autofs4_notify_daemon() may block */
325                 autofs4_notify_daemon(sbi, wq, type);
326         } else {
327                 atomic_inc(&wq->wait_ctr);
328                 mutex_unlock(&sbi->wq_mutex);
329                 kfree(name);
330                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
331                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
332         }
333
334         /* wq->name is NULL if and only if the lock is already released */
335
336         if (sbi->catatonic) {
337                 /* We might have slept, so check again for catatonic mode */
338                 wq->status = -ENOENT;
339                 kfree(wq->name);
340                 wq->name = NULL;
341         }
342
343         if (wq->name) {
344                 /* Block all but "shutdown" signals while waiting */
345                 sigset_t oldset;
346                 unsigned long irqflags;
347
348                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
349                 oldset = current->blocked;
350                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
351                 recalc_sigpending();
352                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
353
354                 wait_event_interruptible(wq->queue, wq->name == NULL);
355
356                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
357                 current->blocked = oldset;
358                 recalc_sigpending();
359                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
360         } else {
361                 DPRINTK("skipped sleeping");
362         }
363
364         status = wq->status;
365
366         /* Are we the last process to need status? */
367         if (atomic_dec_and_test(&wq->wait_ctr))
368                 kfree(wq);
369
370         return status;
371 }
372
373
374 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
375 {
376         struct autofs_wait_queue *wq, **wql;
377
378         mutex_lock(&sbi->wq_mutex);
379         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
380                 if (wq->wait_queue_token == wait_queue_token)
381                         break;
382         }
383
384         if (!wq) {
385                 mutex_unlock(&sbi->wq_mutex);
386                 return -EINVAL;
387         }
388
389         *wql = wq->next;        /* Unlink from chain */
390         mutex_unlock(&sbi->wq_mutex);
391         kfree(wq->name);
392         wq->name = NULL;        /* Do not wait on this queue */
393
394         wq->status = status;
395
396         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
397                 kfree(wq);
398         else
399                 wake_up_interruptible(&wq->queue);
400
401         return 0;
402 }
403