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

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