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