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