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