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         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