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         if (sbi->pipe) {
  45                 fput(sbi->pipe);        /* Close the pipe */
  46                 sbi->pipe = NULL;
  47         }
  48         shrink_dcache_sb(sbi->sb);
  49 }
  50
  51 static int autofs4_write(struct file *file, const void *addr, int bytes)
  52 {
  53         unsigned long sigpipe, flags;
  54         mm_segment_t fs;
  55         const char *data = (const char *)addr;
  56         ssize_t wr = 0;
  57
  58         /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  59
  60         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  61
  62         /* Save pointer to user space and point back to kernel space */
  63         fs = get_fs();
  64         set_fs(KERNEL_DS);
  65
  66         while (bytes &&
  67                (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  68                 data += wr;
  69                 bytes -= wr;
  70         }
  71
  72         set_fs(fs);
  73
  74         /* Keep the currently executing process from receiving a
  75            SIGPIPE unless it was already supposed to get one */
  76         if (wr == -EPIPE && !sigpipe) {
  77                 spin_lock_irqsave(&current->sighand->siglock, flags);
  78                 sigdelset(&current->pending.signal, SIGPIPE);
  79                 recalc_sigpending();
  80                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  81         }
  82
  83         return (bytes > 0);
  84 }
  85
  86 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  87                                  struct autofs_wait_queue *wq,
  88                                  int type)
  89 {
  90         union autofs_packet_union pkt;
  91         size_t pktsz;
  92
  93         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  94                 wq->wait_queue_token, wq->len, wq->name, type);
  95
  96         memset(&pkt,0,sizeof pkt); /* For security reasons */
  97
  98         pkt.hdr.proto_version = sbi->version;
  99         pkt.hdr.type = type;
 100         switch (type) {
 101         /* Kernel protocol v4 missing and expire packets */
 102         case autofs_ptype_missing:
 103         {
 104                 struct autofs_packet_missing *mp = &pkt.missing;
 105
 106                 pktsz = sizeof(*mp);
 107
 108                 mp->wait_queue_token = wq->wait_queue_token;
 109                 mp->len = wq->len;
 110                 memcpy(mp->name, wq->name, wq->len);
 111                 mp->name[wq->len] = '\0';
 112                 break;
 113         }
 114         case autofs_ptype_expire_multi:
 115         {
 116                 struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
 117
 118                 pktsz = sizeof(*ep);
 119
 120                 ep->wait_queue_token = wq->wait_queue_token;
 121                 ep->len = wq->len;
 122                 memcpy(ep->name, wq->name, wq->len);
 123                 ep->name[wq->len] = '\0';
 124                 break;
 125         }
 126         /*
 127          * Kernel protocol v5 packet for handling indirect and direct
 128          * mount missing and expire requests
 129          */
 130         case autofs_ptype_missing_indirect:
 131         case autofs_ptype_expire_indirect:
 132         case autofs_ptype_missing_direct:
 133         case autofs_ptype_expire_direct:
 134         {
 135                 struct autofs_v5_packet *packet = &pkt.v5_packet;
 136
 137                 pktsz = sizeof(*packet);
 138
 139                 packet->wait_queue_token = wq->wait_queue_token;
 140                 packet->len = wq->len;
 141                 memcpy(packet->name, wq->name, wq->len);
 142                 packet->name[wq->len] = '\0';
 143                 packet->dev = wq->dev;
 144                 packet->ino = wq->ino;
 145                 packet->uid = wq->uid;
 146                 packet->gid = wq->gid;
 147                 packet->pid = wq->pid;
 148                 packet->tgid = wq->tgid;
 149                 break;
 150         }
 151         default:
 152                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 153                 return;
 154         }
 155
 156         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 157                 autofs4_catatonic_mode(sbi);
 158 }
 159
 160 static int autofs4_getpath(struct autofs_sb_info *sbi,
 161                            struct dentry *dentry, char **name)
 162 {
 163         struct dentry *root = sbi->sb->s_root;
 164         struct dentry *tmp;
 165         char *buf = *name;
 166         char *p;
 167         int len = 0;
 168
 169         spin_lock(&dcache_lock);
 170         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 171                 len += tmp->d_name.len + 1;
 172
 173         if (--len > NAME_MAX) {
 174                 spin_unlock(&dcache_lock);
 175                 return 0;
 176         }
 177
 178         *(buf + len) = '\0';
 179         p = buf + len - dentry->d_name.len;
 180         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 181
 182         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 183                 *(--p) = '/';
 184                 p -= tmp->d_name.len;
 185                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 186         }
 187         spin_unlock(&dcache_lock);
 188
 189         return len;
 190 }
 191
 192 static struct autofs_wait_queue *
 193 autofs4_find_wait(struct autofs_sb_info *sbi,
 194                   char *name, unsigned int hash, unsigned int len)
 195 {
 196         struct autofs_wait_queue *wq;
 197
 198         for (wq = sbi->queues; wq; wq = wq->next) {
 199                 if (wq->hash == hash &&
 200                     wq->len == len &&
 201                     wq->name && !memcmp(wq->name, name, len))
 202                         break;
 203         }
 204         return wq;
 205 }
 206
 207 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 208                 enum autofs_notify notify)
 209 {
 210         struct autofs_info *ino;
 211         struct autofs_wait_queue *wq;
 212         char *name;
 213         unsigned int len = 0;
 214         unsigned int hash = 0;
 215         int status, type;
 216
 217         /* In catatonic mode, we don't wait for nobody */
 218         if (sbi->catatonic)
 219                 return -ENOENT;
 220
 221         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 222         if (!name)
 223                 return -ENOMEM;
 224
 225         /* If this is a direct mount request create a dummy name */
 226         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
 227                 len = sprintf(name, "%p", dentry);
 228         else {
 229                 len = autofs4_getpath(sbi, dentry, &name);
 230                 if (!len) {
 231                         kfree(name);
 232                         return -ENOENT;
 233                 }
 234         }
 235         hash = full_name_hash(name, len);
 236
 237         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 238                 kfree(name);
 239                 return -EINTR;
 240         }
 241
 242         wq = autofs4_find_wait(sbi, name, hash, len);
 243         ino = autofs4_dentry_ino(dentry);
 244         if (!wq && ino && notify == NFY_NONE) {
 245                 /*
 246                  * Either we've betean the pending expire to post it's
 247                  * wait or it finished while we waited on the mutex.
 248                  * So we need to wait till either, the wait appears
 249                  * or the expire finishes.
 250                  */
 251
 252                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 253                         mutex_unlock(&sbi->wq_mutex);
 254                         schedule_timeout_interruptible(HZ/10);
 255                         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 256                                 kfree(name);
 257                                 return -EINTR;
 258                         }
 259                         wq = autofs4_find_wait(sbi, name, hash, len);
 260                         if (wq)
 261                                 break;
 262                 }
 263
 264                 /*
 265                  * Not ideal but the status has already gone. Of the two
 266                  * cases where we wait on NFY_NONE neither depend on the
 267                  * return status of the wait.
 268                  */
 269                 if (!wq) {
 270                         kfree(name);
 271                         mutex_unlock(&sbi->wq_mutex);
 272                         return 0;
 273                 }
 274         }
 275
 276         if (!wq) {
 277                 /* Create a new wait queue */
 278                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 279                 if (!wq) {
 280                         kfree(name);
 281                         mutex_unlock(&sbi->wq_mutex);
 282                         return -ENOMEM;
 283                 }
 284
 285                 wq->wait_queue_token = autofs4_next_wait_queue;
 286                 if (++autofs4_next_wait_queue == 0)
 287                         autofs4_next_wait_queue = 1;
 288                 wq->next = sbi->queues;
 289                 sbi->queues = wq;
 290                 init_waitqueue_head(&wq->queue);
 291                 wq->hash = hash;
 292                 wq->name = name;
 293                 wq->len = len;
 294                 wq->dev = autofs4_get_dev(sbi);
 295                 wq->ino = autofs4_get_ino(sbi);
 296                 wq->uid = current->uid;
 297                 wq->gid = current->gid;
 298                 wq->pid = current->pid;
 299                 wq->tgid = current->tgid;
 300                 wq->status = -EINTR; /* Status return if interrupted */
 301                 atomic_set(&wq->wait_ctr, 2);
 302                 mutex_unlock(&sbi->wq_mutex);
 303
 304                 if (sbi->version < 5) {
 305                         if (notify == NFY_MOUNT)
 306                                 type = autofs_ptype_missing;
 307                         else
 308                                 type = autofs_ptype_expire_multi;
 309                 } else {
 310                         if (notify == NFY_MOUNT)
 311                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 312                                         autofs_ptype_missing_direct :
 313                                          autofs_ptype_missing_indirect;
 314                         else
 315                                 type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
 316                                         autofs_ptype_expire_direct :
 317                                         autofs_ptype_expire_indirect;
 318                 }
 319
 320                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 321                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 322
 323                 /* autofs4_notify_daemon() may block */
 324                 autofs4_notify_daemon(sbi, wq, type);
 325         } else {
 326                 atomic_inc(&wq->wait_ctr);
 327                 mutex_unlock(&sbi->wq_mutex);
 328                 kfree(name);
 329                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 330                         (unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
 331         }
 332
 333         /* wq->name is NULL if and only if the lock is already released */
 334
 335         if (sbi->catatonic) {
 336                 /* We might have slept, so check again for catatonic mode */
 337                 wq->status = -ENOENT;
 338                 kfree(wq->name);
 339                 wq->name = NULL;
 340         }
 341
 342         if (wq->name) {
 343                 /* Block all but "shutdown" signals while waiting */
 344                 sigset_t oldset;
 345                 unsigned long irqflags;
 346
 347                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 348                 oldset = current->blocked;
 349                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 350                 recalc_sigpending();
 351                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 352
 353                 wait_event_interruptible(wq->queue, wq->name == NULL);
 354
 355                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 356                 current->blocked = oldset;
 357                 recalc_sigpending();
 358                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 359         } else {
 360                 DPRINTK("skipped sleeping");
 361         }
 362
 363         status = wq->status;
 364
 365         /* Are we the last process to need status? */
 366         if (atomic_dec_and_test(&wq->wait_ctr))
 367                 kfree(wq);
 368
 369         return status;
 370 }
 371
 372
 373 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 374 {
 375         struct autofs_wait_queue *wq, **wql;
 376
 377         mutex_lock(&sbi->wq_mutex);
 378         for (wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next) {
 379                 if (wq->wait_queue_token == wait_queue_token)
 380                         break;
 381         }
 382
 383         if (!wq) {
 384                 mutex_unlock(&sbi->wq_mutex);
 385                 return -EINVAL;
 386         }
 387
 388         *wql = wq->next;        /* Unlink from chain */
 389         mutex_unlock(&sbi->wq_mutex);
 390         kfree(wq->name);
 391         wq->name = NULL;        /* Do not wait on this queue */
 392
 393         wq->status = status;
 394
 395         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 396                 kfree(wq);
 397         else
 398                 wake_up_interruptible(&wq->queue);
 399
 400         return 0;
 401 }
 402