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 /*
  96  * The autofs_v5 packet was misdesigned.
  97  *
  98  * The packets are identical on x86-32 and x86-64, but have different
  99  * alignment. Which means that 'sizeof()' will give different results.
 100  * Fix it up for the case of running 32-bit user mode on a 64-bit kernel.
 101  */
 102 static noinline size_t autofs_v5_packet_size(struct autofs_sb_info *sbi)
 103 {
 104         size_t pktsz = sizeof(struct autofs_v5_packet);
 105 #if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
 106         if (sbi->compat_daemon > 0)
 107                 pktsz -= 4;
 108 #endif
 109         return pktsz;
 110 }
 111
 112 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 113                                  struct autofs_wait_queue *wq,
 114                                  int type)
 115 {
 116         union {
 117                 struct autofs_packet_hdr hdr;
 118                 union autofs_packet_union v4_pkt;
 119                 union autofs_v5_packet_union v5_pkt;
 120         } pkt;
 121         struct file *pipe = NULL;
 122         size_t pktsz;
 123
 124         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 125                 (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);
 126
 127         memset(&pkt,0,sizeof pkt); /* For security reasons */
 128
 129         pkt.hdr.proto_version = sbi->version;
 130         pkt.hdr.type = type;
 131         mutex_lock(&sbi->wq_mutex);
 132
 133         /* Check if we have become catatonic */
 134         if (sbi->catatonic) {
 135                 mutex_unlock(&sbi->wq_mutex);
 136                 return;
 137         }
 138         switch (type) {
 139         /* Kernel protocol v4 missing and expire packets */
 140         case autofs_ptype_missing:
 141         {
 142                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 143
 144                 pktsz = sizeof(*mp);
 145
 146                 mp->wait_queue_token = wq->wait_queue_token;
 147                 mp->len = wq->name.len;
 148                 memcpy(mp->name, wq->name.name, wq->name.len);
 149                 mp->name[wq->name.len] = '\0';
 150                 break;
 151         }
 152         case autofs_ptype_expire_multi:
 153         {
 154                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 155
 156                 pktsz = sizeof(*ep);
 157
 158                 ep->wait_queue_token = wq->wait_queue_token;
 159                 ep->len = wq->name.len;
 160                 memcpy(ep->name, wq->name.name, wq->name.len);
 161                 ep->name[wq->name.len] = '\0';
 162                 break;
 163         }
 164         /*
 165          * Kernel protocol v5 packet for handling indirect and direct
 166          * mount missing and expire requests
 167          */
 168         case autofs_ptype_missing_indirect:
 169         case autofs_ptype_expire_indirect:
 170         case autofs_ptype_missing_direct:
 171         case autofs_ptype_expire_direct:
 172         {
 173                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 174
 175                 pktsz = autofs_v5_packet_size(sbi);
 176                 packet->wait_queue_token = wq->wait_queue_token;
 177                 packet->len = wq->name.len;
 178                 memcpy(packet->name, wq->name.name, wq->name.len);
 179                 packet->name[wq->name.len] = '\0';
 180                 packet->dev = wq->dev;
 181                 packet->ino = wq->ino;
 182                 packet->uid = wq->uid;
 183                 packet->gid = wq->gid;
 184                 packet->pid = wq->pid;
 185                 packet->tgid = wq->tgid;
 186                 break;
 187         }
 188         default:
 189                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 190                 mutex_unlock(&sbi->wq_mutex);
 191                 return;
 192         }
 193
 194         pipe = sbi->pipe;
 195         get_file(pipe);
 196
 197         mutex_unlock(&sbi->wq_mutex);
 198
 199         if (autofs4_write(sbi, pipe, &pkt, pktsz))
 200                 autofs4_catatonic_mode(sbi);
 201         fput(pipe);
 202 }
 203
 204 static int autofs4_getpath(struct autofs_sb_info *sbi,
 205                            struct dentry *dentry, char **name)
 206 {
 207         struct dentry *root = sbi->sb->s_root;
 208         struct dentry *tmp;
 209         char *buf;
 210         char *p;
 211         int len;
 212         unsigned seq;
 213
 214 rename_retry:
 215         buf = *name;
 216         len = 0;
 217
 218         seq = read_seqbegin(&rename_lock);
 219         rcu_read_lock();
 220         spin_lock(&sbi->fs_lock);
 221         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 222                 len += tmp->d_name.len + 1;
 223
 224         if (!len || --len > NAME_MAX) {
 225                 spin_unlock(&sbi->fs_lock);
 226                 rcu_read_unlock();
 227                 if (read_seqretry(&rename_lock, seq))
 228                         goto rename_retry;
 229                 return 0;
 230         }
 231
 232         *(buf + len) = '\0';
 233         p = buf + len - dentry->d_name.len;
 234         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 235
 236         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 237                 *(--p) = '/';
 238                 p -= tmp->d_name.len;
 239                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 240         }
 241         spin_unlock(&sbi->fs_lock);
 242         rcu_read_unlock();
 243         if (read_seqretry(&rename_lock, seq))
 244                 goto rename_retry;
 245
 246         return len;
 247 }
 248
 249 static struct autofs_wait_queue *
 250 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 251 {
 252         struct autofs_wait_queue *wq;
 253
 254         for (wq = sbi->queues; wq; wq = wq->next) {
 255                 if (wq->name.hash == qstr->hash &&
 256                     wq->name.len == qstr->len &&
 257                     wq->name.name &&
 258                          !memcmp(wq->name.name, qstr->name, qstr->len))
 259                         break;
 260         }
 261         return wq;
 262 }
 263
 264 /*
 265  * Check if we have a valid request.
 266  * Returns
 267  * 1 if the request should continue.
 268  *   In this case we can return an autofs_wait_queue entry if one is
 269  *   found or NULL to idicate a new wait needs to be created.
 270  * 0 or a negative errno if the request shouldn't continue.
 271  */
 272 static int validate_request(struct autofs_wait_queue **wait,
 273                             struct autofs_sb_info *sbi,
 274                             struct qstr *qstr,
 275                             struct dentry*dentry, enum autofs_notify notify)
 276 {
 277         struct autofs_wait_queue *wq;
 278         struct autofs_info *ino;
 279
 280         if (sbi->catatonic)
 281                 return -ENOENT;
 282
 283         /* Wait in progress, continue; */
 284         wq = autofs4_find_wait(sbi, qstr);
 285         if (wq) {
 286                 *wait = wq;
 287                 return 1;
 288         }
 289
 290         *wait = NULL;
 291
 292         /* If we don't yet have any info this is a new request */
 293         ino = autofs4_dentry_ino(dentry);
 294         if (!ino)
 295                 return 1;
 296
 297         /*
 298          * If we've been asked to wait on an existing expire (NFY_NONE)
 299          * but there is no wait in the queue ...
 300          */
 301         if (notify == NFY_NONE) {
 302                 /*
 303                  * Either we've betean the pending expire to post it's
 304                  * wait or it finished while we waited on the mutex.
 305                  * So we need to wait till either, the wait appears
 306                  * or the expire finishes.
 307                  */
 308
 309                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 310                         mutex_unlock(&sbi->wq_mutex);
 311                         schedule_timeout_interruptible(HZ/10);
 312                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 313                                 return -EINTR;
 314
 315                         if (sbi->catatonic)
 316                                 return -ENOENT;
 317
 318                         wq = autofs4_find_wait(sbi, qstr);
 319                         if (wq) {
 320                                 *wait = wq;
 321                                 return 1;
 322                         }
 323                 }
 324
 325                 /*
 326                  * Not ideal but the status has already gone. Of the two
 327                  * cases where we wait on NFY_NONE neither depend on the
 328                  * return status of the wait.
 329                  */
 330                 return 0;
 331         }
 332
 333         /*
 334          * If we've been asked to trigger a mount and the request
 335          * completed while we waited on the mutex ...
 336          */
 337         if (notify == NFY_MOUNT) {
 338                 struct dentry *new = NULL;
 339                 int valid = 1;
 340
 341                 /*
 342                  * If the dentry was successfully mounted while we slept
 343                  * on the wait queue mutex we can return success. If it
 344                  * isn't mounted (doesn't have submounts for the case of
 345                  * a multi-mount with no mount at it's base) we can
 346                  * continue on and create a new request.
 347                  */
 348                 if (!IS_ROOT(dentry)) {
 349                         if (dentry->d_inode && d_unhashed(dentry)) {
 350                                 struct dentry *parent = dentry->d_parent;
 351                                 new = d_lookup(parent, &dentry->d_name);
 352                                 if (new)
 353                                         dentry = new;
 354                         }
 355                 }
 356                 if (have_submounts(dentry))
 357                         valid = 0;
 358
 359                 if (new)
 360                         dput(new);
 361                 return valid;
 362         }
 363
 364         return 1;
 365 }
 366
 367 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 368                 enum autofs_notify notify)
 369 {
 370         struct autofs_wait_queue *wq;
 371         struct qstr qstr;
 372         char *name;
 373         int status, ret, type;
 374
 375         /* In catatonic mode, we don't wait for nobody */
 376         if (sbi->catatonic)
 377                 return -ENOENT;
 378
 379         if (!dentry->d_inode) {
 380                 /*
 381                  * A wait for a negative dentry is invalid for certain
 382                  * cases. A direct or offset mount "always" has its mount
 383                  * point directory created and so the request dentry must
 384                  * be positive or the map key doesn't exist. The situation
 385                  * is very similar for indirect mounts except only dentrys
 386                  * in the root of the autofs file system may be negative.
 387                  */
 388                 if (autofs_type_trigger(sbi->type))
 389                         return -ENOENT;
 390                 else if (!IS_ROOT(dentry->d_parent))
 391                         return -ENOENT;
 392         }
 393
 394         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 395         if (!name)
 396                 return -ENOMEM;
 397
 398         /* If this is a direct mount request create a dummy name */
 399         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 400                 qstr.len = sprintf(name, "%p", dentry);
 401         else {
 402                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 403                 if (!qstr.len) {
 404                         kfree(name);
 405                         return -ENOENT;
 406                 }
 407         }
 408         qstr.name = name;
 409         qstr.hash = full_name_hash(name, qstr.len);
 410
 411         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 412                 kfree(qstr.name);
 413                 return -EINTR;
 414         }
 415
 416         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 417         if (ret <= 0) {
 418                 if (ret != -EINTR)
 419                         mutex_unlock(&sbi->wq_mutex);
 420                 kfree(qstr.name);
 421                 return ret;
 422         }
 423
 424         if (!wq) {
 425                 /* Create a new wait queue */
 426                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 427                 if (!wq) {
 428                         kfree(qstr.name);
 429                         mutex_unlock(&sbi->wq_mutex);
 430                         return -ENOMEM;
 431                 }
 432
 433                 wq->wait_queue_token = autofs4_next_wait_queue;
 434                 if (++autofs4_next_wait_queue == 0)
 435                         autofs4_next_wait_queue = 1;
 436                 wq->next = sbi->queues;
 437                 sbi->queues = wq;
 438                 init_waitqueue_head(&wq->queue);
 439                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 440                 wq->dev = autofs4_get_dev(sbi);
 441                 wq->ino = autofs4_get_ino(sbi);
 442                 wq->uid = current_uid();
 443                 wq->gid = current_gid();
 444                 wq->pid = current->pid;
 445                 wq->tgid = current->tgid;
 446                 wq->status = -EINTR; /* Status return if interrupted */
 447                 wq->wait_ctr = 2;
 448                 mutex_unlock(&sbi->wq_mutex);
 449
 450                 if (sbi->version < 5) {
 451                         if (notify == NFY_MOUNT)
 452                                 type = autofs_ptype_missing;
 453                         else
 454                                 type = autofs_ptype_expire_multi;
 455                 } else {
 456                         if (notify == NFY_MOUNT)
 457                                 type = autofs_type_trigger(sbi->type) ?
 458                                         autofs_ptype_missing_direct :
 459                                          autofs_ptype_missing_indirect;
 460                         else
 461                                 type = autofs_type_trigger(sbi->type) ?
 462                                         autofs_ptype_expire_direct :
 463                                         autofs_ptype_expire_indirect;
 464                 }
 465
 466                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 467                         (unsigned long) wq->wait_queue_token, wq->name.len,
 468                         wq->name.name, notify);
 469
 470                 /* autofs4_notify_daemon() may block */
 471                 autofs4_notify_daemon(sbi, wq, type);
 472         } else {
 473                 wq->wait_ctr++;
 474                 mutex_unlock(&sbi->wq_mutex);
 475                 kfree(qstr.name);
 476                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 477                         (unsigned long) wq->wait_queue_token, wq->name.len,
 478                         wq->name.name, notify);
 479         }
 480
 481         /*
 482          * wq->name.name is NULL iff the lock is already released
 483          * or the mount has been made catatonic.
 484          */
 485         if (wq->name.name) {
 486                 /* Block all but "shutdown" signals while waiting */
 487                 sigset_t oldset;
 488                 unsigned long irqflags;
 489
 490                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 491                 oldset = current->blocked;
 492                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 493                 recalc_sigpending();
 494                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 495
 496                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 497
 498                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 499                 current->blocked = oldset;
 500                 recalc_sigpending();
 501                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 502         } else {
 503                 DPRINTK("skipped sleeping");
 504         }
 505
 506         status = wq->status;
 507
 508         /*
 509          * For direct and offset mounts we need to track the requester's
 510          * uid and gid in the dentry info struct. This is so it can be
 511          * supplied, on request, by the misc device ioctl interface.
 512          * This is needed during daemon resatart when reconnecting
 513          * to existing, active, autofs mounts. The uid and gid (and
 514          * related string values) may be used for macro substitution
 515          * in autofs mount maps.
 516          */
 517         if (!status) {
 518                 struct autofs_info *ino;
 519                 struct dentry *de = NULL;
 520
 521                 /* direct mount or browsable map */
 522                 ino = autofs4_dentry_ino(dentry);
 523                 if (!ino) {
 524                         /* If not lookup actual dentry used */
 525                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 526                         if (de)
 527                                 ino = autofs4_dentry_ino(de);
 528                 }
 529
 530                 /* Set mount requester */
 531                 if (ino) {
 532                         spin_lock(&sbi->fs_lock);
 533                         ino->uid = wq->uid;
 534                         ino->gid = wq->gid;
 535                         spin_unlock(&sbi->fs_lock);
 536                 }
 537
 538                 if (de)
 539                         dput(de);
 540         }
 541
 542         /* Are we the last process to need status? */
 543         mutex_lock(&sbi->wq_mutex);
 544         if (!--wq->wait_ctr)
 545                 kfree(wq);
 546         mutex_unlock(&sbi->wq_mutex);
 547
 548         return status;
 549 }
 550
 551
 552 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 553 {
 554         struct autofs_wait_queue *wq, **wql;
 555
 556         mutex_lock(&sbi->wq_mutex);
 557         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 558                 if (wq->wait_queue_token == wait_queue_token)
 559                         break;
 560         }
 561
 562         if (!wq) {
 563                 mutex_unlock(&sbi->wq_mutex);
 564                 return -EINVAL;
 565         }
 566
 567         *wql = wq->next;        /* Unlink from chain */
 568         kfree(wq->name.name);
 569         wq->name.name = NULL;   /* Do not wait on this queue */
 570         wq->status = status;
 571         wake_up_interruptible(&wq->queue);
 572         if (!--wq->wait_ctr)
 573                 kfree(wq);
 574         mutex_unlock(&sbi->wq_mutex);
 575
 576         return 0;
 577 }
 578