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Linux/fs/autofs4/waitq.c

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  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         mutex_lock(&sbi->wq_mutex);
 32         if (sbi->catatonic) {
 33                 mutex_unlock(&sbi->wq_mutex);
 34                 return;
 35         }
 36 
 37         DPRINTK("entering catatonic mode");
 38 
 39         sbi->catatonic = 1;
 40         wq = sbi->queues;
 41         sbi->queues = NULL;     /* Erase all wait queues */
 42         while (wq) {
 43                 nwq = wq->next;
 44                 wq->status = -ENOENT; /* Magic is gone - report failure */
 45                 if (wq->name.name) {
 46                         kfree(wq->name.name);
 47                         wq->name.name = NULL;
 48                 }
 49                 wq->wait_ctr--;
 50                 wake_up_interruptible(&wq->queue);
 51                 wq = nwq;
 52         }
 53         fput(sbi->pipe);        /* Close the pipe */
 54         sbi->pipe = NULL;
 55         sbi->pipefd = -1;
 56         mutex_unlock(&sbi->wq_mutex);
 57 }
 58 
 59 static int autofs4_write(struct autofs_sb_info *sbi,
 60                          struct file *file, const void *addr, int bytes)
 61 {
 62         unsigned long sigpipe, flags;
 63         mm_segment_t fs;
 64         const char *data = (const char *)addr;
 65         ssize_t wr = 0;
 66 
 67         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
 68 
 69         /* Save pointer to user space and point back to kernel space */
 70         fs = get_fs();
 71         set_fs(KERNEL_DS);
 72 
 73         mutex_lock(&sbi->pipe_mutex);
 74         while (bytes &&
 75                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
 76                 data += wr;
 77                 bytes -= wr;
 78         }
 79         mutex_unlock(&sbi->pipe_mutex);
 80 
 81         set_fs(fs);
 82 
 83         /* Keep the currently executing process from receiving a
 84            SIGPIPE unless it was already supposed to get one */
 85         if (wr == -EPIPE && !sigpipe) {
 86                 spin_lock_irqsave(&current->sighand->siglock, flags);
 87                 sigdelset(&current->pending.signal, SIGPIPE);
 88                 recalc_sigpending();
 89                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 90         }
 91 
 92         return (bytes > 0);
 93 }
 94         
 95 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 96                                  struct autofs_wait_queue *wq,
 97                                  int type)
 98 {
 99         union {
100                 struct autofs_packet_hdr hdr;
101                 union autofs_packet_union v4_pkt;
102                 union autofs_v5_packet_union v5_pkt;
103         } pkt;
104         struct file *pipe = NULL;
105         size_t pktsz;
106 
107         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
108                 (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);
109 
110         memset(&pkt,0,sizeof pkt); /* For security reasons */
111 
112         pkt.hdr.proto_version = sbi->version;
113         pkt.hdr.type = type;
114         mutex_lock(&sbi->wq_mutex);
115 
116         /* Check if we have become catatonic */
117         if (sbi->catatonic) {
118                 mutex_unlock(&sbi->wq_mutex);
119                 return;
120         }
121         switch (type) {
122         /* Kernel protocol v4 missing and expire packets */
123         case autofs_ptype_missing:
124         {
125                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
126 
127                 pktsz = sizeof(*mp);
128 
129                 mp->wait_queue_token = wq->wait_queue_token;
130                 mp->len = wq->name.len;
131                 memcpy(mp->name, wq->name.name, wq->name.len);
132                 mp->name[wq->name.len] = '\0';
133                 break;
134         }
135         case autofs_ptype_expire_multi:
136         {
137                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
138 
139                 pktsz = sizeof(*ep);
140 
141                 ep->wait_queue_token = wq->wait_queue_token;
142                 ep->len = wq->name.len;
143                 memcpy(ep->name, wq->name.name, wq->name.len);
144                 ep->name[wq->name.len] = '\0';
145                 break;
146         }
147         /*
148          * Kernel protocol v5 packet for handling indirect and direct
149          * mount missing and expire requests
150          */
151         case autofs_ptype_missing_indirect:
152         case autofs_ptype_expire_indirect:
153         case autofs_ptype_missing_direct:
154         case autofs_ptype_expire_direct:
155         {
156                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
157 
158                 pktsz = sizeof(*packet);
159 
160                 packet->wait_queue_token = wq->wait_queue_token;
161                 packet->len = wq->name.len;
162                 memcpy(packet->name, wq->name.name, wq->name.len);
163                 packet->name[wq->name.len] = '\0';
164                 packet->dev = wq->dev;
165                 packet->ino = wq->ino;
166                 packet->uid = wq->uid;
167                 packet->gid = wq->gid;
168                 packet->pid = wq->pid;
169                 packet->tgid = wq->tgid;
170                 break;
171         }
172         default:
173                 printk("autofs4_notify_daemon: bad type %d!\n", type);
174                 mutex_unlock(&sbi->wq_mutex);
175                 return;
176         }
177 
178         pipe = sbi->pipe;
179         get_file(pipe);
180 
181         mutex_unlock(&sbi->wq_mutex);
182 
183         if (autofs4_write(sbi, pipe, &pkt, pktsz))
184                 autofs4_catatonic_mode(sbi);
185         fput(pipe);
186 }
187 
188 static int autofs4_getpath(struct autofs_sb_info *sbi,
189                            struct dentry *dentry, char **name)
190 {
191         struct dentry *root = sbi->sb->s_root;
192         struct dentry *tmp;
193         char *buf;
194         char *p;
195         int len;
196         unsigned seq;
197 
198 rename_retry:
199         buf = *name;
200         len = 0;
201 
202         seq = read_seqbegin(&rename_lock);
203         rcu_read_lock();
204         spin_lock(&sbi->fs_lock);
205         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
206                 len += tmp->d_name.len + 1;
207 
208         if (!len || --len > NAME_MAX) {
209                 spin_unlock(&sbi->fs_lock);
210                 rcu_read_unlock();
211                 if (read_seqretry(&rename_lock, seq))
212                         goto rename_retry;
213                 return 0;
214         }
215 
216         *(buf + len) = '\0';
217         p = buf + len - dentry->d_name.len;
218         strncpy(p, dentry->d_name.name, dentry->d_name.len);
219 
220         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
221                 *(--p) = '/';
222                 p -= tmp->d_name.len;
223                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
224         }
225         spin_unlock(&sbi->fs_lock);
226         rcu_read_unlock();
227         if (read_seqretry(&rename_lock, seq))
228                 goto rename_retry;
229 
230         return len;
231 }
232 
233 static struct autofs_wait_queue *
234 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
235 {
236         struct autofs_wait_queue *wq;
237 
238         for (wq = sbi->queues; wq; wq = wq->next) {
239                 if (wq->name.hash == qstr->hash &&
240                     wq->name.len == qstr->len &&
241                     wq->name.name &&
242                          !memcmp(wq->name.name, qstr->name, qstr->len))
243                         break;
244         }
245         return wq;
246 }
247 
248 /*
249  * Check if we have a valid request.
250  * Returns
251  * 1 if the request should continue.
252  *   In this case we can return an autofs_wait_queue entry if one is
253  *   found or NULL to idicate a new wait needs to be created.
254  * 0 or a negative errno if the request shouldn't continue.
255  */
256 static int validate_request(struct autofs_wait_queue **wait,
257                             struct autofs_sb_info *sbi,
258                             struct qstr *qstr,
259                             struct dentry*dentry, enum autofs_notify notify)
260 {
261         struct autofs_wait_queue *wq;
262         struct autofs_info *ino;
263 
264         if (sbi->catatonic)
265                 return -ENOENT;
266 
267         /* Wait in progress, continue; */
268         wq = autofs4_find_wait(sbi, qstr);
269         if (wq) {
270                 *wait = wq;
271                 return 1;
272         }
273 
274         *wait = NULL;
275 
276         /* If we don't yet have any info this is a new request */
277         ino = autofs4_dentry_ino(dentry);
278         if (!ino)
279                 return 1;
280 
281         /*
282          * If we've been asked to wait on an existing expire (NFY_NONE)
283          * but there is no wait in the queue ...
284          */
285         if (notify == NFY_NONE) {
286                 /*
287                  * Either we've betean the pending expire to post it's
288                  * wait or it finished while we waited on the mutex.
289                  * So we need to wait till either, the wait appears
290                  * or the expire finishes.
291                  */
292 
293                 while (ino->flags & AUTOFS_INF_EXPIRING) {
294                         mutex_unlock(&sbi->wq_mutex);
295                         schedule_timeout_interruptible(HZ/10);
296                         if (mutex_lock_interruptible(&sbi->wq_mutex))
297                                 return -EINTR;
298 
299                         if (sbi->catatonic)
300                                 return -ENOENT;
301 
302                         wq = autofs4_find_wait(sbi, qstr);
303                         if (wq) {
304                                 *wait = wq;
305                                 return 1;
306                         }
307                 }
308 
309                 /*
310                  * Not ideal but the status has already gone. Of the two
311                  * cases where we wait on NFY_NONE neither depend on the
312                  * return status of the wait.
313                  */
314                 return 0;
315         }
316 
317         /*
318          * If we've been asked to trigger a mount and the request
319          * completed while we waited on the mutex ...
320          */
321         if (notify == NFY_MOUNT) {
322                 struct dentry *new = NULL;
323                 int valid = 1;
324 
325                 /*
326                  * If the dentry was successfully mounted while we slept
327                  * on the wait queue mutex we can return success. If it
328                  * isn't mounted (doesn't have submounts for the case of
329                  * a multi-mount with no mount at it's base) we can
330                  * continue on and create a new request.
331                  */
332                 if (!IS_ROOT(dentry)) {
333                         if (dentry->d_inode && d_unhashed(dentry)) {
334                                 struct dentry *parent = dentry->d_parent;
335                                 new = d_lookup(parent, &dentry->d_name);
336                                 if (new)
337                                         dentry = new;
338                         }
339                 }
340                 if (have_submounts(dentry))
341                         valid = 0;
342 
343                 if (new)
344                         dput(new);
345                 return valid;
346         }
347 
348         return 1;
349 }
350 
351 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
352                 enum autofs_notify notify)
353 {
354         struct autofs_wait_queue *wq;
355         struct qstr qstr;
356         char *name;
357         int status, ret, type;
358 
359         /* In catatonic mode, we don't wait for nobody */
360         if (sbi->catatonic)
361                 return -ENOENT;
362 
363         if (!dentry->d_inode) {
364                 /*
365                  * A wait for a negative dentry is invalid for certain
366                  * cases. A direct or offset mount "always" has its mount
367                  * point directory created and so the request dentry must
368                  * be positive or the map key doesn't exist. The situation
369                  * is very similar for indirect mounts except only dentrys
370                  * in the root of the autofs file system may be negative.
371                  */
372                 if (autofs_type_trigger(sbi->type))
373                         return -ENOENT;
374                 else if (!IS_ROOT(dentry->d_parent))
375                         return -ENOENT;
376         }
377 
378         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
379         if (!name)
380                 return -ENOMEM;
381 
382         /* If this is a direct mount request create a dummy name */
383         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
384                 qstr.len = sprintf(name, "%p", dentry);
385         else {
386                 qstr.len = autofs4_getpath(sbi, dentry, &name);
387                 if (!qstr.len) {
388                         kfree(name);
389                         return -ENOENT;
390                 }
391         }
392         qstr.name = name;
393         qstr.hash = full_name_hash(name, qstr.len);
394 
395         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
396                 kfree(qstr.name);
397                 return -EINTR;
398         }
399 
400         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
401         if (ret <= 0) {
402                 if (ret != -EINTR)
403                         mutex_unlock(&sbi->wq_mutex);
404                 kfree(qstr.name);
405                 return ret;
406         }
407 
408         if (!wq) {
409                 /* Create a new wait queue */
410                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
411                 if (!wq) {
412                         kfree(qstr.name);
413                         mutex_unlock(&sbi->wq_mutex);
414                         return -ENOMEM;
415                 }
416 
417                 wq->wait_queue_token = autofs4_next_wait_queue;
418                 if (++autofs4_next_wait_queue == 0)
419                         autofs4_next_wait_queue = 1;
420                 wq->next = sbi->queues;
421                 sbi->queues = wq;
422                 init_waitqueue_head(&wq->queue);
423                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
424                 wq->dev = autofs4_get_dev(sbi);
425                 wq->ino = autofs4_get_ino(sbi);
426                 wq->uid = current_uid();
427                 wq->gid = current_gid();
428                 wq->pid = current->pid;
429                 wq->tgid = current->tgid;
430                 wq->status = -EINTR; /* Status return if interrupted */
431                 wq->wait_ctr = 2;
432                 mutex_unlock(&sbi->wq_mutex);
433 
434                 if (sbi->version < 5) {
435                         if (notify == NFY_MOUNT)
436                                 type = autofs_ptype_missing;
437                         else
438                                 type = autofs_ptype_expire_multi;
439                 } else {
440                         if (notify == NFY_MOUNT)
441                                 type = autofs_type_trigger(sbi->type) ?
442                                         autofs_ptype_missing_direct :
443                                          autofs_ptype_missing_indirect;
444                         else
445                                 type = autofs_type_trigger(sbi->type) ?
446                                         autofs_ptype_expire_direct :
447                                         autofs_ptype_expire_indirect;
448                 }
449 
450                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
451                         (unsigned long) wq->wait_queue_token, wq->name.len,
452                         wq->name.name, notify);
453 
454                 /* autofs4_notify_daemon() may block */
455                 autofs4_notify_daemon(sbi, wq, type);
456         } else {
457                 wq->wait_ctr++;
458                 mutex_unlock(&sbi->wq_mutex);
459                 kfree(qstr.name);
460                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
461                         (unsigned long) wq->wait_queue_token, wq->name.len,
462                         wq->name.name, notify);
463         }
464 
465         /*
466          * wq->name.name is NULL iff the lock is already released
467          * or the mount has been made catatonic.
468          */
469         if (wq->name.name) {
470                 /* Block all but "shutdown" signals while waiting */
471                 sigset_t oldset;
472                 unsigned long irqflags;
473 
474                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
475                 oldset = current->blocked;
476                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
477                 recalc_sigpending();
478                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
479 
480                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
481 
482                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
483                 current->blocked = oldset;
484                 recalc_sigpending();
485                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
486         } else {
487                 DPRINTK("skipped sleeping");
488         }
489 
490         status = wq->status;
491 
492         /*
493          * For direct and offset mounts we need to track the requester's
494          * uid and gid in the dentry info struct. This is so it can be
495          * supplied, on request, by the misc device ioctl interface.
496          * This is needed during daemon resatart when reconnecting
497          * to existing, active, autofs mounts. The uid and gid (and
498          * related string values) may be used for macro substitution
499          * in autofs mount maps.
500          */
501         if (!status) {
502                 struct autofs_info *ino;
503                 struct dentry *de = NULL;
504 
505                 /* direct mount or browsable map */
506                 ino = autofs4_dentry_ino(dentry);
507                 if (!ino) {
508                         /* If not lookup actual dentry used */
509                         de = d_lookup(dentry->d_parent, &dentry->d_name);
510                         if (de)
511                                 ino = autofs4_dentry_ino(de);
512                 }
513 
514                 /* Set mount requester */
515                 if (ino) {
516                         spin_lock(&sbi->fs_lock);
517                         ino->uid = wq->uid;
518                         ino->gid = wq->gid;
519                         spin_unlock(&sbi->fs_lock);
520                 }
521 
522                 if (de)
523                         dput(de);
524         }
525 
526         /* Are we the last process to need status? */
527         mutex_lock(&sbi->wq_mutex);
528         if (!--wq->wait_ctr)
529                 kfree(wq);
530         mutex_unlock(&sbi->wq_mutex);
531 
532         return status;
533 }
534 
535 
536 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
537 {
538         struct autofs_wait_queue *wq, **wql;
539 
540         mutex_lock(&sbi->wq_mutex);
541         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
542                 if (wq->wait_queue_token == wait_queue_token)
543                         break;
544         }
545 
546         if (!wq) {
547                 mutex_unlock(&sbi->wq_mutex);
548                 return -EINVAL;
549         }
550 
551         *wql = wq->next;        /* Unlink from chain */
552         kfree(wq->name.name);
553         wq->name.name = NULL;   /* Do not wait on this queue */
554         wq->status = status;
555         wake_up_interruptible(&wq->queue);
556         if (!--wq->wait_ctr)
557                 kfree(wq);
558         mutex_unlock(&sbi->wq_mutex);
559 
560         return 0;
561 }
562 
563 

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