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