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                 wake_up_interruptible(&wq->queue);
  50                 wq = nwq;
  51         }
  52         fput(sbi->pipe);        /* Close the pipe */
  53         sbi->pipe = NULL;
  54         sbi->pipefd = -1;
  55         mutex_unlock(&sbi->wq_mutex);
  56 }
  57
  58 static int autofs4_write(struct file *file, const void *addr, int bytes)
  59 {
  60         unsigned long sigpipe, flags;
  61         mm_segment_t fs;
  62         const char *data = (const char *)addr;
  63         ssize_t wr = 0;
  64
  65         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  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         while (bytes &&
  74                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  75                 data += wr;
  76                 bytes -= wr;
  77         }
  78
  79         set_fs(fs);
  80
  81         /* Keep the currently executing process from receiving a
  82            SIGPIPE unless it was already supposed to get one */
  83         if (wr == -EPIPE && !sigpipe) {
  84                 spin_lock_irqsave(&current->sighand->siglock, flags);
  85                 sigdelset(&current->pending.signal, SIGPIPE);
  86                 recalc_sigpending();
  87                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  88         }
  89
  90         return (bytes > 0);
  91 }
  92
  93 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  94                                  struct autofs_wait_queue *wq,
  95                                  int type)
  96 {
  97         union {
  98                 struct autofs_packet_hdr hdr;
  99                 union autofs_packet_union v4_pkt;
 100                 union autofs_v5_packet_union v5_pkt;
 101         } pkt;
 102         size_t pktsz;
 103
 104         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 105                 wq->wait_queue_token, wq->name.len, wq->name.name, type);
 106
 107         memset(&pkt,0,sizeof pkt); /* For security reasons */
 108
 109         pkt.hdr.proto_version = sbi->version;
 110         pkt.hdr.type = type;
 111         switch (type) {
 112         /* Kernel protocol v4 missing and expire packets */
 113         case autofs_ptype_missing:
 114         {
 115                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 116
 117                 pktsz = sizeof(*mp);
 118
 119                 mp->wait_queue_token = wq->wait_queue_token;
 120                 mp->len = wq->name.len;
 121                 memcpy(mp->name, wq->name.name, wq->name.len);
 122                 mp->name[wq->name.len] = '\0';
 123                 break;
 124         }
 125         case autofs_ptype_expire_multi:
 126         {
 127                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 128
 129                 pktsz = sizeof(*ep);
 130
 131                 ep->wait_queue_token = wq->wait_queue_token;
 132                 ep->len = wq->name.len;
 133                 memcpy(ep->name, wq->name.name, wq->name.len);
 134                 ep->name[wq->name.len] = '\0';
 135                 break;
 136         }
 137         /*
 138          * Kernel protocol v5 packet for handling indirect and direct
 139          * mount missing and expire requests
 140          */
 141         case autofs_ptype_missing_indirect:
 142         case autofs_ptype_expire_indirect:
 143         case autofs_ptype_missing_direct:
 144         case autofs_ptype_expire_direct:
 145         {
 146                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 147
 148                 pktsz = sizeof(*packet);
 149
 150                 packet->wait_queue_token = wq->wait_queue_token;
 151                 packet->len = wq->name.len;
 152                 memcpy(packet->name, wq->name.name, wq->name.len);
 153                 packet->name[wq->name.len] = '\0';
 154                 packet->dev = wq->dev;
 155                 packet->ino = wq->ino;
 156                 packet->uid = wq->uid;
 157                 packet->gid = wq->gid;
 158                 packet->pid = wq->pid;
 159                 packet->tgid = wq->tgid;
 160                 break;
 161         }
 162         default:
 163                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 164                 return;
 165         }
 166
 167         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 168                 autofs4_catatonic_mode(sbi);
 169 }
 170
 171 static int autofs4_getpath(struct autofs_sb_info *sbi,
 172                            struct dentry *dentry, char **name)
 173 {
 174         struct dentry *root = sbi->sb->s_root;
 175         struct dentry *tmp;
 176         char *buf = *name;
 177         char *p;
 178         int len = 0;
 179
 180         spin_lock(&dcache_lock);
 181         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 182                 len += tmp->d_name.len + 1;
 183
 184         if (!len || --len > NAME_MAX) {
 185                 spin_unlock(&dcache_lock);
 186                 return 0;
 187         }
 188
 189         *(buf + len) = '\0';
 190         p = buf + len - dentry->d_name.len;
 191         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 192
 193         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 194                 *(--p) = '/';
 195                 p -= tmp->d_name.len;
 196                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 197         }
 198         spin_unlock(&dcache_lock);
 199
 200         return len;
 201 }
 202
 203 static struct autofs_wait_queue *
 204 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 205 {
 206         struct autofs_wait_queue *wq;
 207
 208         for (wq = sbi->queues; wq; wq = wq->next) {
 209                 if (wq->name.hash == qstr->hash &&
 210                     wq->name.len == qstr->len &&
 211                     wq->name.name &&
 212                          !memcmp(wq->name.name, qstr->name, qstr->len))
 213                         break;
 214         }
 215         return wq;
 216 }
 217
 218 /*
 219  * Check if we have a valid request.
 220  * Returns
 221  * 1 if the request should continue.
 222  *   In this case we can return an autofs_wait_queue entry if one is
 223  *   found or NULL to idicate a new wait needs to be created.
 224  * 0 or a negative errno if the request shouldn't continue.
 225  */
 226 static int validate_request(struct autofs_wait_queue **wait,
 227                             struct autofs_sb_info *sbi,
 228                             struct qstr *qstr,
 229                             struct dentry*dentry, enum autofs_notify notify)
 230 {
 231         struct autofs_wait_queue *wq;
 232         struct autofs_info *ino;
 233
 234         /* Wait in progress, continue; */
 235         wq = autofs4_find_wait(sbi, qstr);
 236         if (wq) {
 237                 *wait = wq;
 238                 return 1;
 239         }
 240
 241         *wait = NULL;
 242
 243         /* If we don't yet have any info this is a new request */
 244         ino = autofs4_dentry_ino(dentry);
 245         if (!ino)
 246                 return 1;
 247
 248         /*
 249          * If we've been asked to wait on an existing expire (NFY_NONE)
 250          * but there is no wait in the queue ...
 251          */
 252         if (notify == NFY_NONE) {
 253                 /*
 254                  * Either we've betean the pending expire to post it's
 255                  * wait or it finished while we waited on the mutex.
 256                  * So we need to wait till either, the wait appears
 257                  * or the expire finishes.
 258                  */
 259
 260                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 261                         mutex_unlock(&sbi->wq_mutex);
 262                         schedule_timeout_interruptible(HZ/10);
 263                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 264                                 return -EINTR;
 265
 266                         wq = autofs4_find_wait(sbi, qstr);
 267                         if (wq) {
 268                                 *wait = wq;
 269                                 return 1;
 270                         }
 271                 }
 272
 273                 /*
 274                  * Not ideal but the status has already gone. Of the two
 275                  * cases where we wait on NFY_NONE neither depend on the
 276                  * return status of the wait.
 277                  */
 278                 return 0;
 279         }
 280
 281         /*
 282          * If we've been asked to trigger a mount and the request
 283          * completed while we waited on the mutex ...
 284          */
 285         if (notify == NFY_MOUNT) {
 286                 /*
 287                  * If the dentry isn't hashed just go ahead and try the
 288                  * mount again with a new wait (not much else we can do).
 289                 */
 290                 if (!d_unhashed(dentry)) {
 291                         /*
 292                          * But if the dentry is hashed, that means that we
 293                          * got here through the revalidate path.  Thus, we
 294                          * need to check if the dentry has been mounted
 295                          * while we waited on the wq_mutex. If it has,
 296                          * simply return success.
 297                          */
 298                         if (d_mountpoint(dentry))
 299                                 return 0;
 300                 }
 301         }
 302
 303         return 1;
 304 }
 305
 306 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 307                 enum autofs_notify notify)
 308 {
 309         struct autofs_wait_queue *wq;
 310         struct qstr qstr;
 311         char *name;
 312         int status, ret, type;
 313
 314         /* In catatonic mode, we don't wait for nobody */
 315         if (sbi->catatonic)
 316                 return -ENOENT;
 317
 318         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 319         if (!name)
 320                 return -ENOMEM;
 321
 322         /* If this is a direct mount request create a dummy name */
 323         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
 324                 qstr.len = sprintf(name, "%p", dentry);
 325         else {
 326                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 327                 if (!qstr.len) {
 328                         kfree(name);
 329                         return -ENOENT;
 330                 }
 331         }
 332         qstr.name = name;
 333         qstr.hash = full_name_hash(name, qstr.len);
 334
 335         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 336                 kfree(qstr.name);
 337                 return -EINTR;
 338         }
 339
 340         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 341         if (ret <= 0) {
 342                 if (ret == 0)
 343                         mutex_unlock(&sbi->wq_mutex);
 344                 kfree(qstr.name);
 345                 return ret;
 346         }
 347
 348         if (!wq) {
 349                 /* Create a new wait queue */
 350                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 351                 if (!wq) {
 352                         kfree(qstr.name);
 353                         mutex_unlock(&sbi->wq_mutex);
 354                         return -ENOMEM;
 355                 }
 356
 357                 wq->wait_queue_token = autofs4_next_wait_queue;
 358                 if (++autofs4_next_wait_queue == 0)
 359                         autofs4_next_wait_queue = 1;
 360                 wq->next = sbi->queues;
 361                 sbi->queues = wq;
 362                 init_waitqueue_head(&wq->queue);
 363                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 364                 wq->dev = autofs4_get_dev(sbi);
 365                 wq->ino = autofs4_get_ino(sbi);
 366                 wq->uid = current->uid;
 367                 wq->gid = current->gid;
 368                 wq->pid = current->pid;
 369                 wq->tgid = current->tgid;
 370                 wq->status = -EINTR; /* Status return if interrupted */
 371                 atomic_set(&wq->wait_ctr, 2);
 372                 mutex_unlock(&sbi->wq_mutex);
 373
 374                 if (sbi->version < 5) {
 375                         if (notify == NFY_MOUNT)
 376                                 type = autofs_ptype_missing;
 377                         else
 378                                 type = autofs_ptype_expire_multi;
 379                 } else {
 380                         if (notify == NFY_MOUNT)
 381                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 382                                         autofs_ptype_missing_direct :
 383                                          autofs_ptype_missing_indirect;
 384                         else
 385                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 386                                         autofs_ptype_expire_direct :
 387                                         autofs_ptype_expire_indirect;
 388                 }
 389
 390                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 391                         (unsigned long) wq->wait_queue_token, wq->name.len,
 392                         wq->name.name, notify);
 393
 394                 /* autofs4_notify_daemon() may block */
 395                 autofs4_notify_daemon(sbi, wq, type);
 396         } else {
 397                 atomic_inc(&wq->wait_ctr);
 398                 mutex_unlock(&sbi->wq_mutex);
 399                 kfree(qstr.name);
 400                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 401                         (unsigned long) wq->wait_queue_token, wq->name.len,
 402                         wq->name.name, notify);
 403         }
 404
 405         /*
 406          * wq->name.name is NULL iff the lock is already released
 407          * or the mount has been made catatonic.
 408          */
 409         if (wq->name.name) {
 410                 /* Block all but "shutdown" signals while waiting */
 411                 sigset_t oldset;
 412                 unsigned long irqflags;
 413
 414                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 415                 oldset = current->blocked;
 416                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 417                 recalc_sigpending();
 418                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 419
 420                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 421
 422                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 423                 current->blocked = oldset;
 424                 recalc_sigpending();
 425                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 426         } else {
 427                 DPRINTK("skipped sleeping");
 428         }
 429
 430         status = wq->status;
 431
 432         /* Are we the last process to need status? */
 433         if (atomic_dec_and_test(&wq->wait_ctr))
 434                 kfree(wq);
 435
 436         return status;
 437 }
 438
 439
 440 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 441 {
 442         struct autofs_wait_queue *wq, **wql;
 443
 444         mutex_lock(&sbi->wq_mutex);
 445         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 446                 if (wq->wait_queue_token == wait_queue_token)
 447                         break;
 448         }
 449
 450         if (!wq) {
 451                 mutex_unlock(&sbi->wq_mutex);
 452                 return -EINVAL;
 453         }
 454
 455         *wql = wq->next;        /* Unlink from chain */
 456         kfree(wq->name.name);
 457         wq->name.name = NULL;   /* Do not wait on this queue */
 458         mutex_unlock(&sbi->wq_mutex);
 459
 460         wq->status = status;
 461
 462         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 463                 kfree(wq);
 464         else
 465                 wake_up_interruptible(&wq->queue);
 466
 467         return 0;
 468 }
 469