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 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