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                 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 = *name;
 190         char *p;
 191         int len = 0;
 192
 193         spin_lock(&dcache_lock);
 194         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 195                 len += tmp->d_name.len + 1;
 196
 197         if (!len || --len > NAME_MAX) {
 198                 spin_unlock(&dcache_lock);
 199                 return 0;
 200         }
 201
 202         *(buf + len) = '\0';
 203         p = buf + len - dentry->d_name.len;
 204         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 205
 206         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 207                 *(--p) = '/';
 208                 p -= tmp->d_name.len;
 209                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 210         }
 211         spin_unlock(&dcache_lock);
 212
 213         return len;
 214 }
 215
 216 static struct autofs_wait_queue *
 217 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 218 {
 219         struct autofs_wait_queue *wq;
 220
 221         for (wq = sbi->queues; wq; wq = wq->next) {
 222                 if (wq->name.hash == qstr->hash &&
 223                     wq->name.len == qstr->len &&
 224                     wq->name.name &&
 225                          !memcmp(wq->name.name, qstr->name, qstr->len))
 226                         break;
 227         }
 228         return wq;
 229 }
 230
 231 /*
 232  * Check if we have a valid request.
 233  * Returns
 234  * 1 if the request should continue.
 235  *   In this case we can return an autofs_wait_queue entry if one is
 236  *   found or NULL to idicate a new wait needs to be created.
 237  * 0 or a negative errno if the request shouldn't continue.
 238  */
 239 static int validate_request(struct autofs_wait_queue **wait,
 240                             struct autofs_sb_info *sbi,
 241                             struct qstr *qstr,
 242                             struct dentry*dentry, enum autofs_notify notify)
 243 {
 244         struct autofs_wait_queue *wq;
 245         struct autofs_info *ino;
 246
 247         /* Wait in progress, continue; */
 248         wq = autofs4_find_wait(sbi, qstr);
 249         if (wq) {
 250                 *wait = wq;
 251                 return 1;
 252         }
 253
 254         *wait = NULL;
 255
 256         /* If we don't yet have any info this is a new request */
 257         ino = autofs4_dentry_ino(dentry);
 258         if (!ino)
 259                 return 1;
 260
 261         /*
 262          * If we've been asked to wait on an existing expire (NFY_NONE)
 263          * but there is no wait in the queue ...
 264          */
 265         if (notify == NFY_NONE) {
 266                 /*
 267                  * Either we've betean the pending expire to post it's
 268                  * wait or it finished while we waited on the mutex.
 269                  * So we need to wait till either, the wait appears
 270                  * or the expire finishes.
 271                  */
 272
 273                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 274                         mutex_unlock(&sbi->wq_mutex);
 275                         schedule_timeout_interruptible(HZ/10);
 276                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 277                                 return -EINTR;
 278
 279                         wq = autofs4_find_wait(sbi, qstr);
 280                         if (wq) {
 281                                 *wait = wq;
 282                                 return 1;
 283                         }
 284                 }
 285
 286                 /*
 287                  * Not ideal but the status has already gone. Of the two
 288                  * cases where we wait on NFY_NONE neither depend on the
 289                  * return status of the wait.
 290                  */
 291                 return 0;
 292         }
 293
 294         /*
 295          * If we've been asked to trigger a mount and the request
 296          * completed while we waited on the mutex ...
 297          */
 298         if (notify == NFY_MOUNT) {
 299                 /*
 300                  * If the dentry was successfully mounted while we slept
 301                  * on the wait queue mutex we can return success. If it
 302                  * isn't mounted (doesn't have submounts for the case of
 303                  * a multi-mount with no mount at it's base) we can
 304                  * continue on and create a new request.
 305                  */
 306                 if (have_submounts(dentry))
 307                         return 0;
 308         }
 309
 310         return 1;
 311 }
 312
 313 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 314                 enum autofs_notify notify)
 315 {
 316         struct autofs_wait_queue *wq;
 317         struct qstr qstr;
 318         char *name;
 319         int status, ret, type;
 320
 321         /* In catatonic mode, we don't wait for nobody */
 322         if (sbi->catatonic)
 323                 return -ENOENT;
 324
 325         if (!dentry->d_inode) {
 326                 /*
 327                  * A wait for a negative dentry is invalid for certain
 328                  * cases. A direct or offset mount "always" has its mount
 329                  * point directory created and so the request dentry must
 330                  * be positive or the map key doesn't exist. The situation
 331                  * is very similar for indirect mounts except only dentrys
 332                  * in the root of the autofs file system may be negative.
 333                  */
 334                 if (autofs_type_trigger(sbi->type))
 335                         return -ENOENT;
 336                 else if (!IS_ROOT(dentry->d_parent))
 337                         return -ENOENT;
 338         }
 339
 340         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 341         if (!name)
 342                 return -ENOMEM;
 343
 344         /* If this is a direct mount request create a dummy name */
 345         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 346                 qstr.len = sprintf(name, "%p", dentry);
 347         else {
 348                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 349                 if (!qstr.len) {
 350                         kfree(name);
 351                         return -ENOENT;
 352                 }
 353         }
 354         qstr.name = name;
 355         qstr.hash = full_name_hash(name, qstr.len);
 356
 357         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 358                 kfree(qstr.name);
 359                 return -EINTR;
 360         }
 361
 362         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 363         if (ret <= 0) {
 364                 if (ret == 0)
 365                         mutex_unlock(&sbi->wq_mutex);
 366                 kfree(qstr.name);
 367                 return ret;
 368         }
 369
 370         if (!wq) {
 371                 /* Create a new wait queue */
 372                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 373                 if (!wq) {
 374                         kfree(qstr.name);
 375                         mutex_unlock(&sbi->wq_mutex);
 376                         return -ENOMEM;
 377                 }
 378
 379                 wq->wait_queue_token = autofs4_next_wait_queue;
 380                 if (++autofs4_next_wait_queue == 0)
 381                         autofs4_next_wait_queue = 1;
 382                 wq->next = sbi->queues;
 383                 sbi->queues = wq;
 384                 init_waitqueue_head(&wq->queue);
 385                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 386                 wq->dev = autofs4_get_dev(sbi);
 387                 wq->ino = autofs4_get_ino(sbi);
 388                 wq->uid = current_uid();
 389                 wq->gid = current_gid();
 390                 wq->pid = current->pid;
 391                 wq->tgid = current->tgid;
 392                 wq->status = -EINTR; /* Status return if interrupted */
 393                 wq->wait_ctr = 2;
 394                 mutex_unlock(&sbi->wq_mutex);
 395
 396                 if (sbi->version < 5) {
 397                         if (notify == NFY_MOUNT)
 398                                 type = autofs_ptype_missing;
 399                         else
 400                                 type = autofs_ptype_expire_multi;
 401                 } else {
 402                         if (notify == NFY_MOUNT)
 403                                 type = autofs_type_trigger(sbi->type) ?
 404                                         autofs_ptype_missing_direct :
 405                                          autofs_ptype_missing_indirect;
 406                         else
 407                                 type = autofs_type_trigger(sbi->type) ?
 408                                         autofs_ptype_expire_direct :
 409                                         autofs_ptype_expire_indirect;
 410                 }
 411
 412                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 413                         (unsigned long) wq->wait_queue_token, wq->name.len,
 414                         wq->name.name, notify);
 415
 416                 /* autofs4_notify_daemon() may block */
 417                 autofs4_notify_daemon(sbi, wq, type);
 418         } else {
 419                 wq->wait_ctr++;
 420                 mutex_unlock(&sbi->wq_mutex);
 421                 kfree(qstr.name);
 422                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 423                         (unsigned long) wq->wait_queue_token, wq->name.len,
 424                         wq->name.name, notify);
 425         }
 426
 427         /*
 428          * wq->name.name is NULL iff the lock is already released
 429          * or the mount has been made catatonic.
 430          */
 431         if (wq->name.name) {
 432                 /* Block all but "shutdown" signals while waiting */
 433                 sigset_t oldset;
 434                 unsigned long irqflags;
 435
 436                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 437                 oldset = current->blocked;
 438                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 439                 recalc_sigpending();
 440                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 441
 442                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 443
 444                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 445                 current->blocked = oldset;
 446                 recalc_sigpending();
 447                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 448         } else {
 449                 DPRINTK("skipped sleeping");
 450         }
 451
 452         status = wq->status;
 453
 454         /*
 455          * For direct and offset mounts we need to track the requester's
 456          * uid and gid in the dentry info struct. This is so it can be
 457          * supplied, on request, by the misc device ioctl interface.
 458          * This is needed during daemon resatart when reconnecting
 459          * to existing, active, autofs mounts. The uid and gid (and
 460          * related string values) may be used for macro substitution
 461          * in autofs mount maps.
 462          */
 463         if (!status) {
 464                 struct autofs_info *ino;
 465                 struct dentry *de = NULL;
 466
 467                 /* direct mount or browsable map */
 468                 ino = autofs4_dentry_ino(dentry);
 469                 if (!ino) {
 470                         /* If not lookup actual dentry used */
 471                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 472                         if (de)
 473                                 ino = autofs4_dentry_ino(de);
 474                 }
 475
 476                 /* Set mount requester */
 477                 if (ino) {
 478                         spin_lock(&sbi->fs_lock);
 479                         ino->uid = wq->uid;
 480                         ino->gid = wq->gid;
 481                         spin_unlock(&sbi->fs_lock);
 482                 }
 483
 484                 if (de)
 485                         dput(de);
 486         }
 487
 488         /* Are we the last process to need status? */
 489         mutex_lock(&sbi->wq_mutex);
 490         if (!--wq->wait_ctr)
 491                 kfree(wq);
 492         mutex_unlock(&sbi->wq_mutex);
 493
 494         return status;
 495 }
 496
 497
 498 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 499 {
 500         struct autofs_wait_queue *wq, **wql;
 501
 502         mutex_lock(&sbi->wq_mutex);
 503         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 504                 if (wq->wait_queue_token == wait_queue_token)
 505                         break;
 506         }
 507
 508         if (!wq) {
 509                 mutex_unlock(&sbi->wq_mutex);
 510                 return -EINVAL;
 511         }
 512
 513         *wql = wq->next;        /* Unlink from chain */
 514         kfree(wq->name.name);
 515         wq->name.name = NULL;   /* Do not wait on this queue */
 516         wq->status = status;
 517         wake_up_interruptible(&wq->queue);
 518         if (!--wq->wait_ctr)
 519                 kfree(wq);
 520         mutex_unlock(&sbi->wq_mutex);
 521
 522         return 0;
 523 }
 524