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 {
  88                 struct autofs_packet_hdr hdr;
  89                 union autofs_packet_union v4_pkt;
  90                 union autofs_v5_packet_union v5_pkt;
  91         } pkt;
  92         size_t pktsz;
  93
  94         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  95                 wq->wait_queue_token, wq->len, wq->name, type);
  96
  97         memset(&pkt,0,sizeof pkt); /* For security reasons */
  98
  99         pkt.hdr.proto_version = sbi->version;
 100         pkt.hdr.type = type;
 101         switch (type) {
 102         /* Kernel protocol v4 missing and expire packets */
 103         case autofs_ptype_missing:
 104         {
 105                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 106
 107                 pktsz = sizeof(*mp);
 108
 109                 mp->wait_queue_token = wq->wait_queue_token;
 110                 mp->len = wq->len;
 111                 memcpy(mp->name, wq->name, wq->len);
 112                 mp->name[wq->len] = '\0';
 113                 break;
 114         }
 115         case autofs_ptype_expire_multi:
 116         {
 117                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 118
 119                 pktsz = sizeof(*ep);
 120
 121                 ep->wait_queue_token = wq->wait_queue_token;
 122                 ep->len = wq->len;
 123                 memcpy(ep->name, wq->name, wq->len);
 124                 ep->name[wq->len] = '\0';
 125                 break;
 126         }
 127         /*
 128          * Kernel protocol v5 packet for handling indirect and direct
 129          * mount missing and expire requests
 130          */
 131         case autofs_ptype_missing_indirect:
 132         case autofs_ptype_expire_indirect:
 133         case autofs_ptype_missing_direct:
 134         case autofs_ptype_expire_direct:
 135         {
 136                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 137
 138                 pktsz = sizeof(*packet);
 139
 140                 packet->wait_queue_token = wq->wait_queue_token;
 141                 packet->len = wq->len;
 142                 memcpy(packet->name, wq->name, wq->len);
 143                 packet->name[wq->len] = '\0';
 144                 packet->dev = wq->dev;
 145                 packet->ino = wq->ino;
 146                 packet->uid = wq->uid;
 147                 packet->gid = wq->gid;
 148                 packet->pid = wq->pid;
 149                 packet->tgid = wq->tgid;
 150                 break;
 151         }
 152         default:
 153                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 154                 return;
 155         }
 156
 157         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 158                 autofs4_catatonic_mode(sbi);
 159 }
 160
 161 static int autofs4_getpath(struct autofs_sb_info *sbi,
 162                            struct dentry *dentry, char **name)
 163 {
 164         struct dentry *root = sbi->sb->s_root;
 165         struct dentry *tmp;
 166         char *buf = *name;
 167         char *p;
 168         int len = 0;
 169
 170         spin_lock(&dcache_lock);
 171         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 172                 len += tmp->d_name.len + 1;
 173
 174         if (--len > NAME_MAX) {
 175                 spin_unlock(&dcache_lock);
 176                 return 0;
 177         }
 178
 179         *(buf + len) = '\0';
 180         p = buf + len - dentry->d_name.len;
 181         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 182
 183         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 184                 *(--p) = '/';
 185                 p -= tmp->d_name.len;
 186                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 187         }
 188         spin_unlock(&dcache_lock);
 189
 190         return len;
 191 }
 192
 193 static struct autofs_wait_queue *
 194 autofs4_find_wait(struct autofs_sb_info *sbi,
 195                   char *name, unsigned int hash, unsigned int len)
 196 {
 197         struct autofs_wait_queue *wq;
 198
 199         for (wq = sbi->queues; wq; wq = wq->next) {
 200                 if (wq->hash == hash &&
 201                     wq->len == len &&
 202                     wq->name && !memcmp(wq->name, name, len))
 203                         break;
 204         }
 205         return wq;
 206 }
 207
 208 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 209                 enum autofs_notify notify)
 210 {
 211         struct autofs_info *ino;
 212         struct autofs_wait_queue *wq;
 213         char *name;
 214         unsigned int len = 0;
 215         unsigned int hash = 0;
 216         int status, type;
 217
 218         /* In catatonic mode, we don't wait for nobody */
 219         if (sbi->catatonic)
 220                 return -ENOENT;
 221
 222         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 223         if (!name)
 224                 return -ENOMEM;
 225
 226         /* If this is a direct mount request create a dummy name */
 227         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
 228                 len = sprintf(name, "%p", dentry);
 229         else {
 230                 len = autofs4_getpath(sbi, dentry, &name);
 231                 if (!len) {
 232                         kfree(name);
 233                         return -ENOENT;
 234                 }
 235         }
 236         hash = full_name_hash(name, len);
 237
 238         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 239                 kfree(name);
 240                 return -EINTR;
 241         }
 242
 243         wq = autofs4_find_wait(sbi, name, hash, len);
 244         ino = autofs4_dentry_ino(dentry);
 245         if (!wq && ino && notify == NFY_NONE) {
 246                 /*
 247                  * Either we've betean the pending expire to post it's
 248                  * wait or it finished while we waited on the mutex.
 249                  * So we need to wait till either, the wait appears
 250                  * or the expire finishes.
 251                  */
 252
 253                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 254                         mutex_unlock(&sbi->wq_mutex);
 255                         schedule_timeout_interruptible(HZ/10);
 256                         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 257                                 kfree(name);
 258                                 return -EINTR;
 259                         }
 260                         wq = autofs4_find_wait(sbi, name, hash, len);
 261                         if (wq)
 262                                 break;
 263                 }
 264
 265                 /*
 266                  * Not ideal but the status has already gone. Of the two
 267                  * cases where we wait on NFY_NONE neither depend on the
 268                  * return status of the wait.
 269                  */
 270                 if (!wq) {
 271                         kfree(name);
 272                         mutex_unlock(&sbi->wq_mutex);
 273                         return 0;
 274                 }
 275         }
 276
 277         if (!wq) {
 278                 /* Create a new wait queue */
 279                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 280                 if (!wq) {
 281                         kfree(name);
 282                         mutex_unlock(&sbi->wq_mutex);
 283                         return -ENOMEM;
 284                 }
 285
 286                 wq->wait_queue_token = autofs4_next_wait_queue;
 287                 if (++autofs4_next_wait_queue == 0)
 288                         autofs4_next_wait_queue = 1;
 289                 wq->next = sbi->queues;
 290                 sbi->queues = wq;
 291                 init_waitqueue_head(&wq->queue);
 292                 wq->hash = hash;
 293                 wq->name = name;
 294                 wq->len = len;
 295                 wq->dev = autofs4_get_dev(sbi);
 296                 wq->ino = autofs4_get_ino(sbi);
 297                 wq->uid = current->uid;
 298                 wq->gid = current->gid;
 299                 wq->pid = current->pid;
 300                 wq->tgid = current->tgid;
 301                 wq->status = -EINTR; /* Status return if interrupted */
 302                 atomic_set(&wq->wait_ctr, 2);
 303                 mutex_unlock(&sbi->wq_mutex);
 304
 305                 if (sbi->version < 5) {
 306                         if (notify == NFY_MOUNT)
 307                                 type = autofs_ptype_missing;
 308                         else
 309                                 type = autofs_ptype_expire_multi;
 310                 } else {
 311                         if (notify == NFY_MOUNT)
 312                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 313                                         autofs_ptype_missing_direct :
 314                                          autofs_ptype_missing_indirect;
 315                         else
 316                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 317                                         autofs_ptype_expire_direct :
 318                                         autofs_ptype_expire_indirect;
 319                 }
 320
 321                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 322                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 323
 324                 /* autofs4_notify_daemon() may block */
 325                 autofs4_notify_daemon(sbi, wq, type);
 326         } else {
 327                 atomic_inc(&wq->wait_ctr);
 328                 mutex_unlock(&sbi->wq_mutex);
 329                 kfree(name);
 330                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 331                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 332         }
 333
 334         /* wq->name is NULL if and only if the lock is already released */
 335
 336         if (sbi->catatonic) {
 337                 /* We might have slept, so check again for catatonic mode */
 338                 wq->status = -ENOENT;
 339                 kfree(wq->name);
 340                 wq->name = NULL;
 341         }
 342
 343         if (wq->name) {
 344                 /* Block all but "shutdown" signals while waiting */
 345                 sigset_t oldset;
 346                 unsigned long irqflags;
 347
 348                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 349                 oldset = current->blocked;
 350                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 351                 recalc_sigpending();
 352                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 353
 354                 wait_event_interruptible(wq->queue, wq->name == NULL);
 355
 356                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 357                 current->blocked = oldset;
 358                 recalc_sigpending();
 359                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 360         } else {
 361                 DPRINTK("skipped sleeping");
 362         }
 363
 364         status = wq->status;
 365
 366         /* Are we the last process to need status? */
 367         if (atomic_dec_and_test(&wq->wait_ctr))
 368                 kfree(wq);
 369
 370         return status;
 371 }
 372
 373
 374 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 375 {
 376         struct autofs_wait_queue *wq, **wql;
 377
 378         mutex_lock(&sbi->wq_mutex);
 379         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 380                 if (wq->wait_queue_token == wait_queue_token)
 381                         break;
 382         }
 383
 384         if (!wq) {
 385                 mutex_unlock(&sbi->wq_mutex);
 386                 return -EINVAL;
 387         }
 388
 389         *wql = wq->next;        /* Unlink from chain */
 390         mutex_unlock(&sbi->wq_mutex);
 391         kfree(wq->name);
 392         wq->name = NULL;        /* Do not wait on this queue */
 393
 394         wq->status = status;
 395
 396         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 397                 kfree(wq);
 398         else
 399                 wake_up_interruptible(&wq->queue);
 400
 401         return 0;
 402 }
 403