linux/fs/autofs4/waitq.c
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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 */
  22static 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
  27void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  28{
  29        struct autofs_wait_queue *wq, *nwq;
  30
  31        mutex_lock(&sbi->wq_mutex);
  32        if (sbi->catatonic) {
  33                mutex_unlock(&sbi->wq_mutex);
  34                return;
  35        }
  36
  37        DPRINTK("entering catatonic mode");
  38
  39        sbi->catatonic = 1;
  40        wq = sbi->queues;
  41        sbi->queues = NULL;     /* Erase all wait queues */
  42        while (wq) {
  43                nwq = wq->next;
  44                wq->status = -ENOENT; /* Magic is gone - report failure */
  45                if (wq->name.name) {
  46                        kfree(wq->name.name);
  47                        wq->name.name = NULL;
  48                }
  49                wq->wait_ctr--;
  50                wake_up_interruptible(&wq->queue);
  51                wq = nwq;
  52        }
  53        fput(sbi->pipe);        /* Close the pipe */
  54        sbi->pipe = NULL;
  55        sbi->pipefd = -1;
  56        mutex_unlock(&sbi->wq_mutex);
  57}
  58
  59static int autofs4_write(struct file *file, const void *addr, int bytes)
  60{
  61        unsigned long sigpipe, flags;
  62        mm_segment_t fs;
  63        const char *data = (const char *)addr;
  64        ssize_t wr = 0;
  65
  66        /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
  67
  68        sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  69
  70        /* Save pointer to user space and point back to kernel space */
  71        fs = get_fs();
  72        set_fs(KERNEL_DS);
  73
  74        while (bytes &&
  75               (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  76                data += wr;
  77                bytes -= wr;
  78        }
  79
  80        set_fs(fs);
  81
  82        /* Keep the currently executing process from receiving a
  83           SIGPIPE unless it was already supposed to get one */
  84        if (wr == -EPIPE && !sigpipe) {
  85                spin_lock_irqsave(&current->sighand->siglock, flags);
  86                sigdelset(&current->pending.signal, SIGPIPE);
  87                recalc_sigpending();
  88                spin_unlock_irqrestore(&current->sighand->siglock, flags);
  89        }
  90
  91        return (bytes > 0);
  92}
  93        
  94static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  95                                 struct autofs_wait_queue *wq,
  96                                 int type)
  97{
  98        union {
  99                struct autofs_packet_hdr hdr;
 100                union autofs_packet_union v4_pkt;
 101                union autofs_v5_packet_union v5_pkt;
 102        } pkt;
 103        struct file *pipe = NULL;
 104        size_t pktsz;
 105
 106        DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 107                wq->wait_queue_token, wq->name.len, wq->name.name, type);
 108
 109        memset(&pkt,0,sizeof pkt); /* For security reasons */
 110
 111        pkt.hdr.proto_version = sbi->version;
 112        pkt.hdr.type = type;
 113        switch (type) {
 114        /* Kernel protocol v4 missing and expire packets */
 115        case autofs_ptype_missing:
 116        {
 117                struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 118
 119                pktsz = sizeof(*mp);
 120
 121                mp->wait_queue_token = wq->wait_queue_token;
 122                mp->len = wq->name.len;
 123                memcpy(mp->name, wq->name.name, wq->name.len);
 124                mp->name[wq->name.len] = '\0';
 125                break;
 126        }
 127        case autofs_ptype_expire_multi:
 128        {
 129                struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 130
 131                pktsz = sizeof(*ep);
 132
 133                ep->wait_queue_token = wq->wait_queue_token;
 134                ep->len = wq->name.len;
 135                memcpy(ep->name, wq->name.name, wq->name.len);
 136                ep->name[wq->name.len] = '\0';
 137                break;
 138        }
 139        /*
 140         * Kernel protocol v5 packet for handling indirect and direct
 141         * mount missing and expire requests
 142         */
 143        case autofs_ptype_missing_indirect:
 144        case autofs_ptype_expire_indirect:
 145        case autofs_ptype_missing_direct:
 146        case autofs_ptype_expire_direct:
 147        {
 148                struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 149
 150                pktsz = sizeof(*packet);
 151
 152                packet->wait_queue_token = wq->wait_queue_token;
 153                packet->len = wq->name.len;
 154                memcpy(packet->name, wq->name.name, wq->name.len);
 155                packet->name[wq->name.len] = '\0';
 156                packet->dev = wq->dev;
 157                packet->ino = wq->ino;
 158                packet->uid = wq->uid;
 159                packet->gid = wq->gid;
 160                packet->pid = wq->pid;
 161                packet->tgid = wq->tgid;
 162                break;
 163        }
 164        default:
 165                printk("autofs4_notify_daemon: bad type %d!\n", type);
 166                return;
 167        }
 168
 169        /* Check if we have become catatonic */
 170        mutex_lock(&sbi->wq_mutex);
 171        if (!sbi->catatonic) {
 172                pipe = sbi->pipe;
 173                get_file(pipe);
 174        }
 175        mutex_unlock(&sbi->wq_mutex);
 176
 177        if (pipe) {
 178                if (autofs4_write(pipe, &pkt, pktsz))
 179                        autofs4_catatonic_mode(sbi);
 180                fput(pipe);
 181        }
 182}
 183
 184static int autofs4_getpath(struct autofs_sb_info *sbi,
 185                           struct dentry *dentry, char **name)
 186{
 187        struct dentry *root = sbi->sb->s_root;
 188        struct dentry *tmp;
 189        char *buf;
 190        char *p;
 191        int len;
 192        unsigned seq;
 193
 194rename_retry:
 195        buf = *name;
 196        len = 0;
 197
 198        seq = read_seqbegin(&rename_lock);
 199        rcu_read_lock();
 200        spin_lock(&sbi->fs_lock);
 201        for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 202                len += tmp->d_name.len + 1;
 203
 204        if (!len || --len > NAME_MAX) {
 205                spin_unlock(&sbi->fs_lock);
 206                rcu_read_unlock();
 207                if (read_seqretry(&rename_lock, seq))
 208                        goto rename_retry;
 209                return 0;
 210        }
 211
 212        *(buf + len) = '\0';
 213        p = buf + len - dentry->d_name.len;
 214        strncpy(p, dentry->d_name.name, dentry->d_name.len);
 215
 216        for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 217                *(--p) = '/';
 218                p -= tmp->d_name.len;
 219                strncpy(p, tmp->d_name.name, tmp->d_name.len);
 220        }
 221        spin_unlock(&sbi->fs_lock);
 222        rcu_read_unlock();
 223        if (read_seqretry(&rename_lock, seq))
 224                goto rename_retry;
 225
 226        return len;
 227}
 228
 229static struct autofs_wait_queue *
 230autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 231{
 232        struct autofs_wait_queue *wq;
 233
 234        for (wq = sbi->queues; wq; wq = wq->next) {
 235                if (wq->name.hash == qstr->hash &&
 236                    wq->name.len == qstr->len &&
 237                    wq->name.name &&
 238                         !memcmp(wq->name.name, qstr->name, qstr->len))
 239                        break;
 240        }
 241        return wq;
 242}
 243
 244/*
 245 * Check if we have a valid request.
 246 * Returns
 247 * 1 if the request should continue.
 248 *   In this case we can return an autofs_wait_queue entry if one is
 249 *   found or NULL to idicate a new wait needs to be created.
 250 * 0 or a negative errno if the request shouldn't continue.
 251 */
 252static int validate_request(struct autofs_wait_queue **wait,
 253                            struct autofs_sb_info *sbi,
 254                            struct qstr *qstr,
 255                            struct dentry*dentry, enum autofs_notify notify)
 256{
 257        struct autofs_wait_queue *wq;
 258        struct autofs_info *ino;
 259
 260        /* Wait in progress, continue; */
 261        wq = autofs4_find_wait(sbi, qstr);
 262        if (wq) {
 263                *wait = wq;
 264                return 1;
 265        }
 266
 267        *wait = NULL;
 268
 269        /* If we don't yet have any info this is a new request */
 270        ino = autofs4_dentry_ino(dentry);
 271        if (!ino)
 272                return 1;
 273
 274        /*
 275         * If we've been asked to wait on an existing expire (NFY_NONE)
 276         * but there is no wait in the queue ...
 277         */
 278        if (notify == NFY_NONE) {
 279                /*
 280                 * Either we've betean the pending expire to post it's
 281                 * wait or it finished while we waited on the mutex.
 282                 * So we need to wait till either, the wait appears
 283                 * or the expire finishes.
 284                 */
 285
 286                while (ino->flags & AUTOFS_INF_EXPIRING) {
 287                        mutex_unlock(&sbi->wq_mutex);
 288                        schedule_timeout_interruptible(HZ/10);
 289                        if (mutex_lock_interruptible(&sbi->wq_mutex))
 290                                return -EINTR;
 291
 292                        wq = autofs4_find_wait(sbi, qstr);
 293                        if (wq) {
 294                                *wait = wq;
 295                                return 1;
 296                        }
 297                }
 298
 299                /*
 300                 * Not ideal but the status has already gone. Of the two
 301                 * cases where we wait on NFY_NONE neither depend on the
 302                 * return status of the wait.
 303                 */
 304                return 0;
 305        }
 306
 307        /*
 308         * If we've been asked to trigger a mount and the request
 309         * completed while we waited on the mutex ...
 310         */
 311        if (notify == NFY_MOUNT) {
 312                struct dentry *new = NULL;
 313                int valid = 1;
 314
 315                /*
 316                 * If the dentry was successfully mounted while we slept
 317                 * on the wait queue mutex we can return success. If it
 318                 * isn't mounted (doesn't have submounts for the case of
 319                 * a multi-mount with no mount at it's base) we can
 320                 * continue on and create a new request.
 321                 */
 322                if (!IS_ROOT(dentry)) {
 323                        if (dentry->d_inode && d_unhashed(dentry)) {
 324                                struct dentry *parent = dentry->d_parent;
 325                                new = d_lookup(parent, &dentry->d_name);
 326                                if (new)
 327                                        dentry = new;
 328                        }
 329                }
 330                if (have_submounts(dentry))
 331                        valid = 0;
 332
 333                if (new)
 334                        dput(new);
 335                return valid;
 336        }
 337
 338        return 1;
 339}
 340
 341int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 342                enum autofs_notify notify)
 343{
 344        struct autofs_wait_queue *wq;
 345        struct qstr qstr;
 346        char *name;
 347        int status, ret, type;
 348
 349        /* In catatonic mode, we don't wait for nobody */
 350        if (sbi->catatonic)
 351                return -ENOENT;
 352
 353        if (!dentry->d_inode) {
 354                /*
 355                 * A wait for a negative dentry is invalid for certain
 356                 * cases. A direct or offset mount "always" has its mount
 357                 * point directory created and so the request dentry must
 358                 * be positive or the map key doesn't exist. The situation
 359                 * is very similar for indirect mounts except only dentrys
 360                 * in the root of the autofs file system may be negative.
 361                 */
 362                if (autofs_type_trigger(sbi->type))
 363                        return -ENOENT;
 364                else if (!IS_ROOT(dentry->d_parent))
 365                        return -ENOENT;
 366        }
 367
 368        name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 369        if (!name)
 370                return -ENOMEM;
 371
 372        /* If this is a direct mount request create a dummy name */
 373        if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 374                qstr.len = sprintf(name, "%p", dentry);
 375        else {
 376                qstr.len = autofs4_getpath(sbi, dentry, &name);
 377                if (!qstr.len) {
 378                        kfree(name);
 379                        return -ENOENT;
 380                }
 381        }
 382        qstr.name = name;
 383        qstr.hash = full_name_hash(name, qstr.len);
 384
 385        if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 386                kfree(qstr.name);
 387                return -EINTR;
 388        }
 389
 390        ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 391        if (ret <= 0) {
 392                if (ret == 0)
 393                        mutex_unlock(&sbi->wq_mutex);
 394                kfree(qstr.name);
 395                return ret;
 396        }
 397
 398        if (!wq) {
 399                /* Create a new wait queue */
 400                wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 401                if (!wq) {
 402                        kfree(qstr.name);
 403                        mutex_unlock(&sbi->wq_mutex);
 404                        return -ENOMEM;
 405                }
 406
 407                wq->wait_queue_token = autofs4_next_wait_queue;
 408                if (++autofs4_next_wait_queue == 0)
 409                        autofs4_next_wait_queue = 1;
 410                wq->next = sbi->queues;
 411                sbi->queues = wq;
 412                init_waitqueue_head(&wq->queue);
 413                memcpy(&wq->name, &qstr, sizeof(struct qstr));
 414                wq->dev = autofs4_get_dev(sbi);
 415                wq->ino = autofs4_get_ino(sbi);
 416                wq->uid = current_uid();
 417                wq->gid = current_gid();
 418                wq->pid = current->pid;
 419                wq->tgid = current->tgid;
 420                wq->status = -EINTR; /* Status return if interrupted */
 421                wq->wait_ctr = 2;
 422                mutex_unlock(&sbi->wq_mutex);
 423
 424                if (sbi->version < 5) {
 425                        if (notify == NFY_MOUNT)
 426                                type = autofs_ptype_missing;
 427                        else
 428                                type = autofs_ptype_expire_multi;
 429                } else {
 430                        if (notify == NFY_MOUNT)
 431                                type = autofs_type_trigger(sbi->type) ?
 432                                        autofs_ptype_missing_direct :
 433                                         autofs_ptype_missing_indirect;
 434                        else
 435                                type = autofs_type_trigger(sbi->type) ?
 436                                        autofs_ptype_expire_direct :
 437                                        autofs_ptype_expire_indirect;
 438                }
 439
 440                DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 441                        (unsigned long) wq->wait_queue_token, wq->name.len,
 442                        wq->name.name, notify);
 443
 444                /* autofs4_notify_daemon() may block */
 445                autofs4_notify_daemon(sbi, wq, type);
 446        } else {
 447                wq->wait_ctr++;
 448                mutex_unlock(&sbi->wq_mutex);
 449                kfree(qstr.name);
 450                DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 451                        (unsigned long) wq->wait_queue_token, wq->name.len,
 452                        wq->name.name, notify);
 453        }
 454
 455        /*
 456         * wq->name.name is NULL iff the lock is already released
 457         * or the mount has been made catatonic.
 458         */
 459        if (wq->name.name) {
 460                /* Block all but "shutdown" signals while waiting */
 461                sigset_t oldset;
 462                unsigned long irqflags;
 463
 464                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 465                oldset = current->blocked;
 466                siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 467                recalc_sigpending();
 468                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 469
 470                wait_event_interruptible(wq->queue, wq->name.name == NULL);
 471
 472                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 473                current->blocked = oldset;
 474                recalc_sigpending();
 475                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 476        } else {
 477                DPRINTK("skipped sleeping");
 478        }
 479
 480        status = wq->status;
 481
 482        /*
 483         * For direct and offset mounts we need to track the requester's
 484         * uid and gid in the dentry info struct. This is so it can be
 485         * supplied, on request, by the misc device ioctl interface.
 486         * This is needed during daemon resatart when reconnecting
 487         * to existing, active, autofs mounts. The uid and gid (and
 488         * related string values) may be used for macro substitution
 489         * in autofs mount maps.
 490         */
 491        if (!status) {
 492                struct autofs_info *ino;
 493                struct dentry *de = NULL;
 494
 495                /* direct mount or browsable map */
 496                ino = autofs4_dentry_ino(dentry);
 497                if (!ino) {
 498                        /* If not lookup actual dentry used */
 499                        de = d_lookup(dentry->d_parent, &dentry->d_name);
 500                        if (de)
 501                                ino = autofs4_dentry_ino(de);
 502                }
 503
 504                /* Set mount requester */
 505                if (ino) {
 506                        spin_lock(&sbi->fs_lock);
 507                        ino->uid = wq->uid;
 508                        ino->gid = wq->gid;
 509                        spin_unlock(&sbi->fs_lock);
 510                }
 511
 512                if (de)
 513                        dput(de);
 514        }
 515
 516        /* Are we the last process to need status? */
 517        mutex_lock(&sbi->wq_mutex);
 518        if (!--wq->wait_ctr)
 519                kfree(wq);
 520        mutex_unlock(&sbi->wq_mutex);
 521
 522        return status;
 523}
 524
 525
 526int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 527{
 528        struct autofs_wait_queue *wq, **wql;
 529
 530        mutex_lock(&sbi->wq_mutex);
 531        for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 532                if (wq->wait_queue_token == wait_queue_token)
 533                        break;
 534        }
 535
 536        if (!wq) {
 537                mutex_unlock(&sbi->wq_mutex);
 538                return -EINVAL;
 539        }
 540
 541        *wql = wq->next;        /* Unlink from chain */
 542        kfree(wq->name.name);
 543        wq->name.name = NULL;   /* Do not wait on this queue */
 544        wq->status = status;
 545        wake_up_interruptible(&wq->queue);
 546        if (!--wq->wait_ctr)
 547                kfree(wq);
 548        mutex_unlock(&sbi->wq_mutex);
 549
 550        return 0;
 551}
 552
 553