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         DPRINTK("entering catatonic mode");
  32
  33         sbi->catatonic = 1;
  34         wq = sbi->queues;
  35         sbi->queues = NULL;     /* Erase all wait queues */
  36         while (wq) {
  37                 nwq = wq->next;
  38                 wq->status = -ENOENT; /* Magic is gone - report failure */
  39                 kfree(wq->name);
  40                 wq->name = NULL;
  41                 wake_up_interruptible(&wq->queue);
  42                 wq = nwq;
  43         }
  44         fput(sbi->pipe);        /* Close the pipe */
  45         sbi->pipe = NULL;
  46 }
  47
  48 static int autofs4_write(struct file *file, const void *addr, int bytes)
  49 {
  50         unsigned long sigpipe, flags;
  51         mm_segment_t fs;
  52         const char *data = (const char *)addr;
  53         ssize_t wr = 0;
  54
  55         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  56
  57         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  58
  59         /* Save pointer to user space and point back to kernel space */
  60         fs = get_fs();
  61         set_fs(KERNEL_DS);
  62
  63         while (bytes &&
  64                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  65                 data += wr;
  66                 bytes -= wr;
  67         }
  68
  69         set_fs(fs);
  70
  71         /* Keep the currently executing process from receiving a
  72            SIGPIPE unless it was already supposed to get one */
  73         if (wr == -EPIPE && !sigpipe) {
  74                 spin_lock_irqsave(&current->sighand->siglock, flags);
  75                 sigdelset(&current->pending.signal, SIGPIPE);
  76                 recalc_sigpending();
  77                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  78         }
  79
  80         return (bytes > 0);
  81 }
  82
  83 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  84                                  struct autofs_wait_queue *wq,
  85                                  int type)
  86 {
  87         union autofs_packet_union pkt;
  88         size_t pktsz;
  89
  90         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  91                 wq->wait_queue_token, wq->len, wq->name, type);
  92
  93         memset(&pkt,0,sizeof pkt); /* For security reasons */
  94
  95         pkt.hdr.proto_version = sbi->version;
  96         pkt.hdr.type = type;
  97         switch (type) {
  98         /* Kernel protocol v4 missing and expire packets */
  99         case autofs_ptype_missing:
 100         {
 101                 struct autofs_packet_missing *mp = &pkt.missing;
 102
 103                 pktsz = sizeof(*mp);
 104
 105                 mp->wait_queue_token = wq->wait_queue_token;
 106                 mp->len = wq->len;
 107                 memcpy(mp->name, wq->name, wq->len);
 108                 mp->name[wq->len] = '\0';
 109                 break;
 110         }
 111         case autofs_ptype_expire_multi:
 112         {
 113                 struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
 114
 115                 pktsz = sizeof(*ep);
 116
 117                 ep->wait_queue_token = wq->wait_queue_token;
 118                 ep->len = wq->len;
 119                 memcpy(ep->name, wq->name, wq->len);
 120                 ep->name[wq->len] = '\0';
 121                 break;
 122         }
 123         /*
 124          * Kernel protocol v5 packet for handling indirect and direct
 125          * mount missing and expire requests
 126          */
 127         case autofs_ptype_missing_indirect:
 128         case autofs_ptype_expire_indirect:
 129         case autofs_ptype_missing_direct:
 130         case autofs_ptype_expire_direct:
 131         {
 132                 struct autofs_v5_packet *packet = &pkt.v5_packet;
 133
 134                 pktsz = sizeof(*packet);
 135
 136                 packet->wait_queue_token = wq->wait_queue_token;
 137                 packet->len = wq->len;
 138                 memcpy(packet->name, wq->name, wq->len);
 139                 packet->name[wq->len] = '\0';
 140                 packet->dev = wq->dev;
 141                 packet->ino = wq->ino;
 142                 packet->uid = wq->uid;
 143                 packet->gid = wq->gid;
 144                 packet->pid = wq->pid;
 145                 packet->tgid = wq->tgid;
 146                 break;
 147         }
 148         default:
 149                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 150                 return;
 151         }
 152
 153         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 154                 autofs4_catatonic_mode(sbi);
 155 }
 156
 157 static int autofs4_getpath(struct autofs_sb_info *sbi,
 158                            struct dentry *dentry, char **name)
 159 {
 160         struct dentry *root = sbi->sb->s_root;
 161         struct dentry *tmp;
 162         char *buf = *name;
 163         char *p;
 164         int len = 0;
 165
 166         spin_lock(&dcache_lock);
 167         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 168                 len += tmp->d_name.len + 1;
 169
 170         if (--len > NAME_MAX) {
 171                 spin_unlock(&dcache_lock);
 172                 return 0;
 173         }
 174
 175         *(buf + len) = '\0';
 176         p = buf + len - dentry->d_name.len;
 177         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 178
 179         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 180                 *(--p) = '/';
 181                 p -= tmp->d_name.len;
 182                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 183         }
 184         spin_unlock(&dcache_lock);
 185
 186         return len;
 187 }
 188
 189 static struct autofs_wait_queue *
 190 autofs4_find_wait(struct autofs_sb_info *sbi,
 191                   char *name, unsigned int hash, unsigned int len)
 192 {
 193         struct autofs_wait_queue *wq;
 194
 195         for (wq = sbi->queues; wq; wq = wq->next) {
 196                 if (wq->hash == hash &&
 197                     wq->len == len &&
 198                     wq->name && !memcmp(wq->name, name, len))
 199                         break;
 200         }
 201         return wq;
 202 }
 203
 204 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 205                 enum autofs_notify notify)
 206 {
 207         struct autofs_info *ino;
 208         struct autofs_wait_queue *wq;
 209         char *name;
 210         unsigned int len = 0;
 211         unsigned int hash = 0;
 212         int status, type;
 213
 214         /* In catatonic mode, we don't wait for nobody */
 215         if (sbi->catatonic)
 216                 return -ENOENT;
 217
 218         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 219         if (!name)
 220                 return -ENOMEM;
 221
 222         /* If this is a direct mount request create a dummy name */
 223         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
 224                 len = sprintf(name, "%p", dentry);
 225         else {
 226                 len = autofs4_getpath(sbi, dentry, &name);
 227                 if (!len) {
 228                         kfree(name);
 229                         return -ENOENT;
 230                 }
 231         }
 232         hash = full_name_hash(name, len);
 233
 234         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 235                 kfree(name);
 236                 return -EINTR;
 237         }
 238
 239         wq = autofs4_find_wait(sbi, name, hash, len);
 240         ino = autofs4_dentry_ino(dentry);
 241         if (!wq && ino && notify == NFY_NONE) {
 242                 /*
 243                  * Either we've betean the pending expire to post it's
 244                  * wait or it finished while we waited on the mutex.
 245                  * So we need to wait till either, the wait appears
 246                  * or the expire finishes.
 247                  */
 248
 249                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 250                         mutex_unlock(&sbi->wq_mutex);
 251                         schedule_timeout_interruptible(HZ/10);
 252                         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 253                                 kfree(name);
 254                                 return -EINTR;
 255                         }
 256                         wq = autofs4_find_wait(sbi, name, hash, len);
 257                         if (wq)
 258                                 break;
 259                 }
 260
 261                 /*
 262                  * Not ideal but the status has already gone. Of the two
 263                  * cases where we wait on NFY_NONE neither depend on the
 264                  * return status of the wait.
 265                  */
 266                 if (!wq) {
 267                         kfree(name);
 268                         mutex_unlock(&sbi->wq_mutex);
 269                         return 0;
 270                 }
 271         }
 272
 273         if (!wq) {
 274                 /* Create a new wait queue */
 275                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 276                 if (!wq) {
 277                         kfree(name);
 278                         mutex_unlock(&sbi->wq_mutex);
 279                         return -ENOMEM;
 280                 }
 281
 282                 wq->wait_queue_token = autofs4_next_wait_queue;
 283                 if (++autofs4_next_wait_queue == 0)
 284                         autofs4_next_wait_queue = 1;
 285                 wq->next = sbi->queues;
 286                 sbi->queues = wq;
 287                 init_waitqueue_head(&wq->queue);
 288                 wq->hash = hash;
 289                 wq->name = name;
 290                 wq->len = len;
 291                 wq->dev = autofs4_get_dev(sbi);
 292                 wq->ino = autofs4_get_ino(sbi);
 293                 wq->uid = current->uid;
 294                 wq->gid = current->gid;
 295                 wq->pid = current->pid;
 296                 wq->tgid = current->tgid;
 297                 wq->status = -EINTR; /* Status return if interrupted */
 298                 atomic_set(&wq->wait_ctr, 2);
 299                 mutex_unlock(&sbi->wq_mutex);
 300
 301                 if (sbi->version < 5) {
 302                         if (notify == NFY_MOUNT)
 303                                 type = autofs_ptype_missing;
 304                         else
 305                                 type = autofs_ptype_expire_multi;
 306                 } else {
 307                         if (notify == NFY_MOUNT)
 308                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 309                                         autofs_ptype_missing_direct :
 310                                          autofs_ptype_missing_indirect;
 311                         else
 312                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 313                                         autofs_ptype_expire_direct :
 314                                         autofs_ptype_expire_indirect;
 315                 }
 316
 317                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 318                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 319
 320                 /* autofs4_notify_daemon() may block */
 321                 autofs4_notify_daemon(sbi, wq, type);
 322         } else {
 323                 atomic_inc(&wq->wait_ctr);
 324                 mutex_unlock(&sbi->wq_mutex);
 325                 kfree(name);
 326                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 327                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 328         }
 329
 330         /* wq->name is NULL if and only if the lock is already released */
 331
 332         if (sbi->catatonic) {
 333                 /* We might have slept, so check again for catatonic mode */
 334                 wq->status = -ENOENT;
 335                 kfree(wq->name);
 336                 wq->name = NULL;
 337         }
 338
 339         if (wq->name) {
 340                 /* Block all but "shutdown" signals while waiting */
 341                 sigset_t oldset;
 342                 unsigned long irqflags;
 343
 344                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 345                 oldset = current->blocked;
 346                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 347                 recalc_sigpending();
 348                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 349
 350                 wait_event_interruptible(wq->queue, wq->name == NULL);
 351
 352                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 353                 current->blocked = oldset;
 354                 recalc_sigpending();
 355                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 356         } else {
 357                 DPRINTK("skipped sleeping");
 358         }
 359
 360         status = wq->status;
 361
 362         /* Are we the last process to need status? */
 363         if (atomic_dec_and_test(&wq->wait_ctr))
 364                 kfree(wq);
 365
 366         return status;
 367 }
 368
 369
 370 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 371 {
 372         struct autofs_wait_queue *wq, **wql;
 373
 374         mutex_lock(&sbi->wq_mutex);
 375         for (wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next) {
 376                 if (wq->wait_queue_token == wait_queue_token)
 377                         break;
 378         }
 379
 380         if (!wq) {
 381                 mutex_unlock(&sbi->wq_mutex);
 382                 return -EINVAL;
 383         }
 384
 385         *wql = wq->next;        /* Unlink from chain */
 386         mutex_unlock(&sbi->wq_mutex);
 387         kfree(wq->name);
 388         wq->name = NULL;        /* Do not wait on this queue */
 389
 390         wq->status = status;
 391
 392         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 393                 kfree(wq);
 394         else
 395                 wake_up_interruptible(&wq->queue);
 396
 397         return 0;
 398 }
 399