[PATCH] Make most file operations structs in fs/ const
[linux-2.6.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         if (sbi->pipe) {
45                 fput(sbi->pipe);        /* Close the pipe */
46                 sbi->pipe = NULL;
47         }
48         shrink_dcache_sb(sbi->sb);
49 }
50
51 static int autofs4_write(struct file *file, const void *addr, int bytes)
52 {
53         unsigned long sigpipe, flags;
54         mm_segment_t fs;
55         const char *data = (const char *)addr;
56         ssize_t wr = 0;
57
58         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
59
60         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
61
62         /* Save pointer to user space and point back to kernel space */
63         fs = get_fs();
64         set_fs(KERNEL_DS);
65
66         while (bytes &&
67                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
68                 data += wr;
69                 bytes -= wr;
70         }
71
72         set_fs(fs);
73
74         /* Keep the currently executing process from receiving a
75            SIGPIPE unless it was already supposed to get one */
76         if (wr == -EPIPE && !sigpipe) {
77                 spin_lock_irqsave(&current->sighand->siglock, flags);
78                 sigdelset(&current->pending.signal, SIGPIPE);
79                 recalc_sigpending();
80                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
81         }
82
83         return (bytes > 0);
84 }
85         
86 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
87                                  struct autofs_wait_queue *wq,
88                                  int type)
89 {
90         union autofs_packet_union pkt;
91         size_t pktsz;
92
93         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
94                 wq->wait_queue_token, wq->len, wq->name, type);
95
96         memset(&pkt,0,sizeof pkt); /* For security reasons */
97
98         pkt.hdr.proto_version = sbi->version;
99         pkt.hdr.type = type;
100         switch (type) {
101         /* Kernel protocol v4 missing and expire packets */
102         case autofs_ptype_missing:
103         {
104                 struct autofs_packet_missing *mp = &pkt.missing;
105
106                 pktsz = sizeof(*mp);
107
108                 mp->wait_queue_token = wq->wait_queue_token;
109                 mp->len = wq->len;
110                 memcpy(mp->name, wq->name, wq->len);
111                 mp->name[wq->len] = '\0';
112                 break;
113         }
114         case autofs_ptype_expire_multi:
115         {
116                 struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
117
118                 pktsz = sizeof(*ep);
119
120                 ep->wait_queue_token = wq->wait_queue_token;
121                 ep->len = wq->len;
122                 memcpy(ep->name, wq->name, wq->len);
123                 ep->name[wq->len] = '\0';
124                 break;
125         }
126         /*
127          * Kernel protocol v5 packet for handling indirect and direct
128          * mount missing and expire requests
129          */
130         case autofs_ptype_missing_indirect:
131         case autofs_ptype_expire_indirect:
132         case autofs_ptype_missing_direct:
133         case autofs_ptype_expire_direct:
134         {
135                 struct autofs_v5_packet *packet = &pkt.v5_packet;
136
137                 pktsz = sizeof(*packet);
138
139                 packet->wait_queue_token = wq->wait_queue_token;
140                 packet->len = wq->len;
141                 memcpy(packet->name, wq->name, wq->len);
142                 packet->name[wq->len] = '\0';
143                 packet->dev = wq->dev;
144                 packet->ino = wq->ino;
145                 packet->uid = wq->uid;
146                 packet->gid = wq->gid;
147                 packet->pid = wq->pid;
148                 packet->tgid = wq->tgid;
149                 break;
150         }
151         default:
152                 printk("autofs4_notify_daemon: bad type %d!\n", type);
153                 return;
154         }
155
156         if (autofs4_write(sbi->pipe, &pkt, pktsz))
157                 autofs4_catatonic_mode(sbi);
158 }
159
160 static int autofs4_getpath(struct autofs_sb_info *sbi,
161                            struct dentry *dentry, char **name)
162 {
163         struct dentry *root = sbi->sb->s_root;
164         struct dentry *tmp;
165         char *buf = *name;
166         char *p;
167         int len = 0;
168
169         spin_lock(&dcache_lock);
170         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
171                 len += tmp->d_name.len + 1;
172
173         if (--len > NAME_MAX) {
174                 spin_unlock(&dcache_lock);
175                 return 0;
176         }
177
178         *(buf + len) = '\0';
179         p = buf + len - dentry->d_name.len;
180         strncpy(p, dentry->d_name.name, dentry->d_name.len);
181
182         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
183                 *(--p) = '/';
184                 p -= tmp->d_name.len;
185                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
186         }
187         spin_unlock(&dcache_lock);
188
189         return len;
190 }
191
192 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
193                 enum autofs_notify notify)
194 {
195         struct autofs_wait_queue *wq;
196         char *name;
197         unsigned int len = 0;
198         unsigned int hash = 0;
199         int status;
200
201         /* In catatonic mode, we don't wait for nobody */
202         if (sbi->catatonic)
203                 return -ENOENT;
204         
205         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
206         if (!name)
207                 return -ENOMEM;
208
209         /* If this is a direct mount request create a dummy name */
210         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
211                 len = sprintf(name, "%p", dentry);
212         else {
213                 len = autofs4_getpath(sbi, dentry, &name);
214                 if (!len) {
215                         kfree(name);
216                         return -ENOENT;
217                 }
218         }
219         hash = full_name_hash(name, len);
220
221         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
222                 kfree(name);
223                 return -EINTR;
224         }
225
226         for (wq = sbi->queues ; wq ; wq = wq->next) {
227                 if (wq->hash == dentry->d_name.hash &&
228                     wq->len == len &&
229                     wq->name && !memcmp(wq->name, name, len))
230                         break;
231         }
232
233         if (!wq) {
234                 /* Can't wait for an expire if there's no mount */
235                 if (notify == NFY_NONE && !d_mountpoint(dentry)) {
236                         kfree(name);
237                         mutex_unlock(&sbi->wq_mutex);
238                         return -ENOENT;
239                 }
240
241                 /* Create a new wait queue */
242                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
243                 if (!wq) {
244                         kfree(name);
245                         mutex_unlock(&sbi->wq_mutex);
246                         return -ENOMEM;
247                 }
248
249                 wq->wait_queue_token = autofs4_next_wait_queue;
250                 if (++autofs4_next_wait_queue == 0)
251                         autofs4_next_wait_queue = 1;
252                 wq->next = sbi->queues;
253                 sbi->queues = wq;
254                 init_waitqueue_head(&wq->queue);
255                 wq->hash = hash;
256                 wq->name = name;
257                 wq->len = len;
258                 wq->dev = autofs4_get_dev(sbi);
259                 wq->ino = autofs4_get_ino(sbi);
260                 wq->uid = current->uid;
261                 wq->gid = current->gid;
262                 wq->pid = current->pid;
263                 wq->tgid = current->tgid;
264                 wq->status = -EINTR; /* Status return if interrupted */
265                 atomic_set(&wq->wait_ctr, 2);
266                 atomic_set(&wq->notify, 1);
267                 mutex_unlock(&sbi->wq_mutex);
268         } else {
269                 atomic_inc(&wq->wait_ctr);
270                 mutex_unlock(&sbi->wq_mutex);
271                 kfree(name);
272                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
273                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
274         }
275
276         if (notify != NFY_NONE && atomic_read(&wq->notify)) {
277                 int type;
278
279                 atomic_dec(&wq->notify);
280
281                 if (sbi->version < 5) {
282                         if (notify == NFY_MOUNT)
283                                 type = autofs_ptype_missing;
284                         else
285                                 type = autofs_ptype_expire_multi;
286                 } else {
287                         if (notify == NFY_MOUNT)
288                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
289                                         autofs_ptype_missing_direct :
290                                          autofs_ptype_missing_indirect;
291                         else
292                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
293                                         autofs_ptype_expire_direct :
294                                         autofs_ptype_expire_indirect;
295                 }
296
297                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
298                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
299
300                 /* autofs4_notify_daemon() may block */
301                 autofs4_notify_daemon(sbi, wq, type);
302         }
303
304         /* wq->name is NULL if and only if the lock is already released */
305
306         if (sbi->catatonic) {
307                 /* We might have slept, so check again for catatonic mode */
308                 wq->status = -ENOENT;
309                 kfree(wq->name);
310                 wq->name = NULL;
311         }
312
313         if (wq->name) {
314                 /* Block all but "shutdown" signals while waiting */
315                 sigset_t oldset;
316                 unsigned long irqflags;
317
318                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
319                 oldset = current->blocked;
320                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
321                 recalc_sigpending();
322                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
323
324                 wait_event_interruptible(wq->queue, wq->name == NULL);
325
326                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
327                 current->blocked = oldset;
328                 recalc_sigpending();
329                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
330         } else {
331                 DPRINTK("skipped sleeping");
332         }
333
334         status = wq->status;
335
336         /* Are we the last process to need status? */
337         if (atomic_dec_and_test(&wq->wait_ctr))
338                 kfree(wq);
339
340         return status;
341 }
342
343
344 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
345 {
346         struct autofs_wait_queue *wq, **wql;
347
348         mutex_lock(&sbi->wq_mutex);
349         for (wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next) {
350                 if (wq->wait_queue_token == wait_queue_token)
351                         break;
352         }
353
354         if (!wq) {
355                 mutex_unlock(&sbi->wq_mutex);
356                 return -EINVAL;
357         }
358
359         *wql = wq->next;        /* Unlink from chain */
360         mutex_unlock(&sbi->wq_mutex);
361         kfree(wq->name);
362         wq->name = NULL;        /* Do not wait on this queue */
363
364         wq->status = status;
365
366         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
367                 kfree(wq);
368         else
369                 wake_up_interruptible(&wq->queue);
370
371         return 0;
372 }
373