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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 
113         switch (type) {
114         /* Kernel protocol v4 missing and expire packets */
115         case autofs_ptype_missing:
116         {
117                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
118 
119                 pktsz = sizeof(*mp);
120 
121                 mp->wait_queue_token = wq->wait_queue_token;
122                 mp->len = wq->name.len;
123                 memcpy(mp->name, wq->name.name, wq->name.len);
124                 mp->name[wq->name.len] = '\0';
125                 break;
126         }
127         case autofs_ptype_expire_multi:
128         {
129                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
130 
131                 pktsz = sizeof(*ep);
132 
133                 ep->wait_queue_token = wq->wait_queue_token;
134                 ep->len = wq->name.len;
135                 memcpy(ep->name, wq->name.name, wq->name.len);
136                 ep->name[wq->name.len] = '\0';
137                 break;
138         }
139         /*
140          * Kernel protocol v5 packet for handling indirect and direct
141          * mount missing and expire requests
142          */
143         case autofs_ptype_missing_indirect:
144         case autofs_ptype_expire_indirect:
145         case autofs_ptype_missing_direct:
146         case autofs_ptype_expire_direct:
147         {
148                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
149                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
150 
151                 pktsz = sizeof(*packet);
152 
153                 packet->wait_queue_token = wq->wait_queue_token;
154                 packet->len = wq->name.len;
155                 memcpy(packet->name, wq->name.name, wq->name.len);
156                 packet->name[wq->name.len] = '\0';
157                 packet->dev = wq->dev;
158                 packet->ino = wq->ino;
159                 packet->uid = from_kuid_munged(user_ns, wq->uid);
160                 packet->gid = from_kgid_munged(user_ns, wq->gid);
161                 packet->pid = wq->pid;
162                 packet->tgid = wq->tgid;
163                 break;
164         }
165         default:
166                 printk("autofs4_notify_daemon: bad type %d!\n", type);
167                 mutex_unlock(&sbi->wq_mutex);
168                 return;
169         }
170 
171         pipe = get_file(sbi->pipe);
172 
173         mutex_unlock(&sbi->wq_mutex);
174 
175         if (autofs4_write(sbi, pipe, &pkt, pktsz))
176                 autofs4_catatonic_mode(sbi);
177         fput(pipe);
178 }
179 
180 static int autofs4_getpath(struct autofs_sb_info *sbi,
181                            struct dentry *dentry, char **name)
182 {
183         struct dentry *root = sbi->sb->s_root;
184         struct dentry *tmp;
185         char *buf;
186         char *p;
187         int len;
188         unsigned seq;
189 
190 rename_retry:
191         buf = *name;
192         len = 0;
193 
194         seq = read_seqbegin(&rename_lock);
195         rcu_read_lock();
196         spin_lock(&sbi->fs_lock);
197         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
198                 len += tmp->d_name.len + 1;
199 
200         if (!len || --len > NAME_MAX) {
201                 spin_unlock(&sbi->fs_lock);
202                 rcu_read_unlock();
203                 if (read_seqretry(&rename_lock, seq))
204                         goto rename_retry;
205                 return 0;
206         }
207 
208         *(buf + len) = '\0';
209         p = buf + len - dentry->d_name.len;
210         strncpy(p, dentry->d_name.name, dentry->d_name.len);
211 
212         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
213                 *(--p) = '/';
214                 p -= tmp->d_name.len;
215                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
216         }
217         spin_unlock(&sbi->fs_lock);
218         rcu_read_unlock();
219         if (read_seqretry(&rename_lock, seq))
220                 goto rename_retry;
221 
222         return len;
223 }
224 
225 static struct autofs_wait_queue *
226 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
227 {
228         struct autofs_wait_queue *wq;
229 
230         for (wq = sbi->queues; wq; wq = wq->next) {
231                 if (wq->name.hash == qstr->hash &&
232                     wq->name.len == qstr->len &&
233                     wq->name.name &&
234                          !memcmp(wq->name.name, qstr->name, qstr->len))
235                         break;
236         }
237         return wq;
238 }
239 
240 /*
241  * Check if we have a valid request.
242  * Returns
243  * 1 if the request should continue.
244  *   In this case we can return an autofs_wait_queue entry if one is
245  *   found or NULL to idicate a new wait needs to be created.
246  * 0 or a negative errno if the request shouldn't continue.
247  */
248 static int validate_request(struct autofs_wait_queue **wait,
249                             struct autofs_sb_info *sbi,
250                             struct qstr *qstr,
251                             struct dentry*dentry, enum autofs_notify notify)
252 {
253         struct autofs_wait_queue *wq;
254         struct autofs_info *ino;
255 
256         if (sbi->catatonic)
257                 return -ENOENT;
258 
259         /* Wait in progress, continue; */
260         wq = autofs4_find_wait(sbi, qstr);
261         if (wq) {
262                 *wait = wq;
263                 return 1;
264         }
265 
266         *wait = NULL;
267 
268         /* If we don't yet have any info this is a new request */
269         ino = autofs4_dentry_ino(dentry);
270         if (!ino)
271                 return 1;
272 
273         /*
274          * If we've been asked to wait on an existing expire (NFY_NONE)
275          * but there is no wait in the queue ...
276          */
277         if (notify == NFY_NONE) {
278                 /*
279                  * Either we've betean the pending expire to post it's
280                  * wait or it finished while we waited on the mutex.
281                  * So we need to wait till either, the wait appears
282                  * or the expire finishes.
283                  */
284 
285                 while (ino->flags & AUTOFS_INF_EXPIRING) {
286                         mutex_unlock(&sbi->wq_mutex);
287                         schedule_timeout_interruptible(HZ/10);
288                         if (mutex_lock_interruptible(&sbi->wq_mutex))
289                                 return -EINTR;
290 
291                         if (sbi->catatonic)
292                                 return -ENOENT;
293 
294                         wq = autofs4_find_wait(sbi, qstr);
295                         if (wq) {
296                                 *wait = wq;
297                                 return 1;
298                         }
299                 }
300 
301                 /*
302                  * Not ideal but the status has already gone. Of the two
303                  * cases where we wait on NFY_NONE neither depend on the
304                  * return status of the wait.
305                  */
306                 return 0;
307         }
308 
309         /*
310          * If we've been asked to trigger a mount and the request
311          * completed while we waited on the mutex ...
312          */
313         if (notify == NFY_MOUNT) {
314                 struct dentry *new = NULL;
315                 int valid = 1;
316 
317                 /*
318                  * If the dentry was successfully mounted while we slept
319                  * on the wait queue mutex we can return success. If it
320                  * isn't mounted (doesn't have submounts for the case of
321                  * a multi-mount with no mount at it's base) we can
322                  * continue on and create a new request.
323                  */
324                 if (!IS_ROOT(dentry)) {
325                         if (dentry->d_inode && d_unhashed(dentry)) {
326                                 struct dentry *parent = dentry->d_parent;
327                                 new = d_lookup(parent, &dentry->d_name);
328                                 if (new)
329                                         dentry = new;
330                         }
331                 }
332                 if (have_submounts(dentry))
333                         valid = 0;
334 
335                 if (new)
336                         dput(new);
337                 return valid;
338         }
339 
340         return 1;
341 }
342 
343 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
344                 enum autofs_notify notify)
345 {
346         struct autofs_wait_queue *wq;
347         struct qstr qstr;
348         char *name;
349         int status, ret, type;
350         pid_t pid;
351         pid_t tgid;
352 
353         /* In catatonic mode, we don't wait for nobody */
354         if (sbi->catatonic)
355                 return -ENOENT;
356 
357         /*
358          * Try translating pids to the namespace of the daemon.
359          *
360          * Zero means failure: we are in an unrelated pid namespace.
361          */
362         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
363         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
364         if (pid == 0 || tgid == 0)
365                 return -ENOENT;
366 
367         if (!dentry->d_inode) {
368                 /*
369                  * A wait for a negative dentry is invalid for certain
370                  * cases. A direct or offset mount "always" has its mount
371                  * point directory created and so the request dentry must
372                  * be positive or the map key doesn't exist. The situation
373                  * is very similar for indirect mounts except only dentrys
374                  * in the root of the autofs file system may be negative.
375                  */
376                 if (autofs_type_trigger(sbi->type))
377                         return -ENOENT;
378                 else if (!IS_ROOT(dentry->d_parent))
379                         return -ENOENT;
380         }
381 
382         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
383         if (!name)
384                 return -ENOMEM;
385 
386         /* If this is a direct mount request create a dummy name */
387         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
388                 qstr.len = sprintf(name, "%p", dentry);
389         else {
390                 qstr.len = autofs4_getpath(sbi, dentry, &name);
391                 if (!qstr.len) {
392                         kfree(name);
393                         return -ENOENT;
394                 }
395         }
396         qstr.name = name;
397         qstr.hash = full_name_hash(name, qstr.len);
398 
399         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
400                 kfree(qstr.name);
401                 return -EINTR;
402         }
403 
404         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
405         if (ret <= 0) {
406                 if (ret != -EINTR)
407                         mutex_unlock(&sbi->wq_mutex);
408                 kfree(qstr.name);
409                 return ret;
410         }
411 
412         if (!wq) {
413                 /* Create a new wait queue */
414                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
415                 if (!wq) {
416                         kfree(qstr.name);
417                         mutex_unlock(&sbi->wq_mutex);
418                         return -ENOMEM;
419                 }
420 
421                 wq->wait_queue_token = autofs4_next_wait_queue;
422                 if (++autofs4_next_wait_queue == 0)
423                         autofs4_next_wait_queue = 1;
424                 wq->next = sbi->queues;
425                 sbi->queues = wq;
426                 init_waitqueue_head(&wq->queue);
427                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
428                 wq->dev = autofs4_get_dev(sbi);
429                 wq->ino = autofs4_get_ino(sbi);
430                 wq->uid = current_uid();
431                 wq->gid = current_gid();
432                 wq->pid = pid;
433                 wq->tgid = tgid;
434                 wq->status = -EINTR; /* Status return if interrupted */
435                 wq->wait_ctr = 2;
436 
437                 if (sbi->version < 5) {
438                         if (notify == NFY_MOUNT)
439                                 type = autofs_ptype_missing;
440                         else
441                                 type = autofs_ptype_expire_multi;
442                 } else {
443                         if (notify == NFY_MOUNT)
444                                 type = autofs_type_trigger(sbi->type) ?
445                                         autofs_ptype_missing_direct :
446                                          autofs_ptype_missing_indirect;
447                         else
448                                 type = autofs_type_trigger(sbi->type) ?
449                                         autofs_ptype_expire_direct :
450                                         autofs_ptype_expire_indirect;
451                 }
452 
453                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
454                         (unsigned long) wq->wait_queue_token, wq->name.len,
455                         wq->name.name, notify);
456 
457                 /* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
458                 autofs4_notify_daemon(sbi, wq, type);
459         } else {
460                 wq->wait_ctr++;
461                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
462                         (unsigned long) wq->wait_queue_token, wq->name.len,
463                         wq->name.name, notify);
464                 mutex_unlock(&sbi->wq_mutex);
465                 kfree(qstr.name);
466         }
467 
468         /*
469          * wq->name.name is NULL iff the lock is already released
470          * or the mount has been made catatonic.
471          */
472         if (wq->name.name) {
473                 /* Block all but "shutdown" signals while waiting */
474                 sigset_t oldset;
475                 unsigned long irqflags;
476 
477                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
478                 oldset = current->blocked;
479                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
480                 recalc_sigpending();
481                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
482 
483                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
484 
485                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
486                 current->blocked = oldset;
487                 recalc_sigpending();
488                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
489         } else {
490                 DPRINTK("skipped sleeping");
491         }
492 
493         status = wq->status;
494 
495         /*
496          * For direct and offset mounts we need to track the requester's
497          * uid and gid in the dentry info struct. This is so it can be
498          * supplied, on request, by the misc device ioctl interface.
499          * This is needed during daemon resatart when reconnecting
500          * to existing, active, autofs mounts. The uid and gid (and
501          * related string values) may be used for macro substitution
502          * in autofs mount maps.
503          */
504         if (!status) {
505                 struct autofs_info *ino;
506                 struct dentry *de = NULL;
507 
508                 /* direct mount or browsable map */
509                 ino = autofs4_dentry_ino(dentry);
510                 if (!ino) {
511                         /* If not lookup actual dentry used */
512                         de = d_lookup(dentry->d_parent, &dentry->d_name);
513                         if (de)
514                                 ino = autofs4_dentry_ino(de);
515                 }
516 
517                 /* Set mount requester */
518                 if (ino) {
519                         spin_lock(&sbi->fs_lock);
520                         ino->uid = wq->uid;
521                         ino->gid = wq->gid;
522                         spin_unlock(&sbi->fs_lock);
523                 }
524 
525                 if (de)
526                         dput(de);
527         }
528 
529         /* Are we the last process to need status? */
530         mutex_lock(&sbi->wq_mutex);
531         if (!--wq->wait_ctr)
532                 kfree(wq);
533         mutex_unlock(&sbi->wq_mutex);
534 
535         return status;
536 }
537 
538 
539 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
540 {
541         struct autofs_wait_queue *wq, **wql;
542 
543         mutex_lock(&sbi->wq_mutex);
544         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
545                 if (wq->wait_queue_token == wait_queue_token)
546                         break;
547         }
548 
549         if (!wq) {
550                 mutex_unlock(&sbi->wq_mutex);
551                 return -EINVAL;
552         }
553 
554         *wql = wq->next;        /* Unlink from chain */
555         kfree(wq->name.name);
556         wq->name.name = NULL;   /* Do not wait on this queue */
557         wq->status = status;
558         wake_up_interruptible(&wq->queue);
559         if (!--wq->wait_ctr)
560                 kfree(wq);
561         mutex_unlock(&sbi->wq_mutex);
562 
563         return 0;
564 }
565 
566 

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