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   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                 if (wq->name.name) {
  40                         kfree(wq->name.name);
  41                         wq->name.name = NULL;
  42                 }
  43                 wake_up_interruptible(&wq->queue);
  44                 wq = nwq;
  45         }
  46         fput(sbi->pipe);        /* Close the pipe */
  47         sbi->pipe = NULL;
  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 {
  90                 struct autofs_packet_hdr hdr;
  91                 union autofs_packet_union v4_pkt;
  92                 union autofs_v5_packet_union v5_pkt;
  93         } pkt;
  94         size_t pktsz;
  95
  96         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
  97                 wq->wait_queue_token, wq->name.len, wq->name.name, type);
  98
  99         memset(&pkt,0,sizeof pkt); /* For security reasons */
 100
 101         pkt.hdr.proto_version = sbi->version;
 102         pkt.hdr.type = type;
 103         switch (type) {
 104         /* Kernel protocol v4 missing and expire packets */
 105         case autofs_ptype_missing:
 106         {
 107                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 108
 109                 pktsz = sizeof(*mp);
 110
 111                 mp->wait_queue_token = wq->wait_queue_token;
 112                 mp->len = wq->name.len;
 113                 memcpy(mp->name, wq->name.name, wq->name.len);
 114                 mp->name[wq->name.len] = '\0';
 115                 break;
 116         }
 117         case autofs_ptype_expire_multi:
 118         {
 119                 struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 120
 121                 pktsz = sizeof(*ep);
 122
 123                 ep->wait_queue_token = wq->wait_queue_token;
 124                 ep->len = wq->name.len;
 125                 memcpy(ep->name, wq->name.name, wq->name.len);
 126                 ep->name[wq->name.len] = '\0';
 127                 break;
 128         }
 129         /*
 130          * Kernel protocol v5 packet for handling indirect and direct
 131          * mount missing and expire requests
 132          */
 133         case autofs_ptype_missing_indirect:
 134         case autofs_ptype_expire_indirect:
 135         case autofs_ptype_missing_direct:
 136         case autofs_ptype_expire_direct:
 137         {
 138                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 139
 140                 pktsz = sizeof(*packet);
 141
 142                 packet->wait_queue_token = wq->wait_queue_token;
 143                 packet->len = wq->name.len;
 144                 memcpy(packet->name, wq->name.name, wq->name.len);
 145                 packet->name[wq->name.len] = '\0';
 146                 packet->dev = wq->dev;
 147                 packet->ino = wq->ino;
 148                 packet->uid = wq->uid;
 149                 packet->gid = wq->gid;
 150                 packet->pid = wq->pid;
 151                 packet->tgid = wq->tgid;
 152                 break;
 153         }
 154         default:
 155                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 156                 return;
 157         }
 158
 159         if (autofs4_write(sbi->pipe, &pkt, pktsz))
 160                 autofs4_catatonic_mode(sbi);
 161 }
 162
 163 static int autofs4_getpath(struct autofs_sb_info *sbi,
 164                            struct dentry *dentry, char **name)
 165 {
 166         struct dentry *root = sbi->sb->s_root;
 167         struct dentry *tmp;
 168         char *buf = *name;
 169         char *p;
 170         int len = 0;
 171
 172         spin_lock(&dcache_lock);
 173         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 174                 len += tmp->d_name.len + 1;
 175
 176         if (!len || --len > NAME_MAX) {
 177                 spin_unlock(&dcache_lock);
 178                 return 0;
 179         }
 180
 181         *(buf + len) = '\0';
 182         p = buf + len - dentry->d_name.len;
 183         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 184
 185         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 186                 *(--p) = '/';
 187                 p -= tmp->d_name.len;
 188                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 189         }
 190         spin_unlock(&dcache_lock);
 191
 192         return len;
 193 }
 194
 195 static struct autofs_wait_queue *
 196 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 197 {
 198         struct autofs_wait_queue *wq;
 199
 200         for (wq = sbi->queues; wq; wq = wq->next) {
 201                 if (wq->name.hash == qstr->hash &&
 202                     wq->name.len == qstr->len &&
 203                     wq->name.name &&
 204                          !memcmp(wq->name.name, qstr->name, qstr->len))
 205                         break;
 206         }
 207         return wq;
 208 }
 209
 210 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 211                 enum autofs_notify notify)
 212 {
 213         struct autofs_info *ino;
 214         struct autofs_wait_queue *wq;
 215         struct qstr qstr;
 216         char *name;
 217         int status, type;
 218
 219         /* In catatonic mode, we don't wait for nobody */
 220         if (sbi->catatonic)
 221                 return -ENOENT;
 222
 223         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 224         if (!name)
 225                 return -ENOMEM;
 226
 227         /* If this is a direct mount request create a dummy name */
 228         if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
 229                 qstr.len = sprintf(name, "%p", dentry);
 230         else {
 231                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 232                 if (!qstr.len) {
 233                         kfree(name);
 234                         return -ENOENT;
 235                 }
 236         }
 237         qstr.name = name;
 238         qstr.hash = full_name_hash(name, qstr.len);
 239
 240         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 241                 kfree(qstr.name);
 242                 return -EINTR;
 243         }
 244
 245         wq = autofs4_find_wait(sbi, &qstr);
 246         ino = autofs4_dentry_ino(dentry);
 247         if (!wq && ino && notify == NFY_NONE) {
 248                 /*
 249                  * Either we've betean the pending expire to post it's
 250                  * wait or it finished while we waited on the mutex.
 251                  * So we need to wait till either, the wait appears
 252                  * or the expire finishes.
 253                  */
 254
 255                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 256                         mutex_unlock(&sbi->wq_mutex);
 257                         schedule_timeout_interruptible(HZ/10);
 258                         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 259                                 kfree(qstr.name);
 260                                 return -EINTR;
 261                         }
 262                         wq = autofs4_find_wait(sbi, &qstr);
 263                         if (wq)
 264                                 break;
 265                 }
 266
 267                 /*
 268                  * Not ideal but the status has already gone. Of the two
 269                  * cases where we wait on NFY_NONE neither depend on the
 270                  * return status of the wait.
 271                  */
 272                 if (!wq) {
 273                         kfree(qstr.name);
 274                         mutex_unlock(&sbi->wq_mutex);
 275                         return 0;
 276                 }
 277         }
 278
 279         if (!wq) {
 280                 /* Create a new wait queue */
 281                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 282                 if (!wq) {
 283                         kfree(qstr.name);
 284                         mutex_unlock(&sbi->wq_mutex);
 285                         return -ENOMEM;
 286                 }
 287
 288                 wq->wait_queue_token = autofs4_next_wait_queue;
 289                 if (++autofs4_next_wait_queue == 0)
 290                         autofs4_next_wait_queue = 1;
 291                 wq->next = sbi->queues;
 292                 sbi->queues = wq;
 293                 init_waitqueue_head(&wq->queue);
 294                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 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->name.len,
 323                         wq->name.name, notify);
 324
 325                 /* autofs4_notify_daemon() may block */
 326                 autofs4_notify_daemon(sbi, wq, type);
 327         } else {
 328                 atomic_inc(&wq->wait_ctr);
 329                 mutex_unlock(&sbi->wq_mutex);
 330                 kfree(qstr.name);
 331                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 332                         (unsigned long) wq->wait_queue_token, wq->name.len,
 333                         wq->name.name, notify);
 334         }
 335
 336         /* wq->name is NULL if and only if the lock is already released */
 337
 338         if (sbi->catatonic) {
 339                 /* We might have slept, so check again for catatonic mode */
 340                 wq->status = -ENOENT;
 341                 if (wq->name.name) {
 342                         kfree(wq->name.name);
 343                         wq->name.name = NULL;
 344                 }
 345         }
 346
 347         if (wq->name.name) {
 348                 /* Block all but "shutdown" signals while waiting */
 349                 sigset_t oldset;
 350                 unsigned long irqflags;
 351
 352                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 353                 oldset = current->blocked;
 354                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 355                 recalc_sigpending();
 356                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 357
 358                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 359
 360                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 361                 current->blocked = oldset;
 362                 recalc_sigpending();
 363                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 364         } else {
 365                 DPRINTK("skipped sleeping");
 366         }
 367
 368         status = wq->status;
 369
 370         /* Are we the last process to need status? */
 371         if (atomic_dec_and_test(&wq->wait_ctr))
 372                 kfree(wq);
 373
 374         return status;
 375 }
 376
 377
 378 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 379 {
 380         struct autofs_wait_queue *wq, **wql;
 381
 382         mutex_lock(&sbi->wq_mutex);
 383         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 384                 if (wq->wait_queue_token == wait_queue_token)
 385                         break;
 386         }
 387
 388         if (!wq) {
 389                 mutex_unlock(&sbi->wq_mutex);
 390                 return -EINVAL;
 391         }
 392
 393         *wql = wq->next;        /* Unlink from chain */
 394         mutex_unlock(&sbi->wq_mutex);
 395         kfree(wq->name.name);
 396         wq->name.name = NULL;   /* Do not wait on this queue */
 397
 398         wq->status = status;
 399
 400         if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
 401                 kfree(wq);
 402         else
 403                 wake_up_interruptible(&wq->queue);
 404
 405         return 0;
 406 }
 407