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 autofs_sb_info *sbi,
  60                         struct file *file, const void *addr, int bytes)
  61{
  62        unsigned long sigpipe, flags;
  63        mm_segment_t fs;
  64        const char *data = (const char *)addr;
  65        ssize_t wr = 0;
  66
  67        sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  68
  69        /* Save pointer to user space and point back to kernel space */
  70        fs = get_fs();
  71        set_fs(KERNEL_DS);
  72
  73        mutex_lock(&sbi->pipe_mutex);
  74        while (bytes &&
  75               (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  76                data += wr;
  77                bytes -= wr;
  78        }
  79        mutex_unlock(&sbi->pipe_mutex);
  80
  81        set_fs(fs);
  82
  83        /* Keep the currently executing process from receiving a
  84           SIGPIPE unless it was already supposed to get one */
  85        if (wr == -EPIPE && !sigpipe) {
  86                spin_lock_irqsave(&current->sighand->siglock, flags);
  87                sigdelset(&current->pending.signal, SIGPIPE);
  88                recalc_sigpending();
  89                spin_unlock_irqrestore(&current->sighand->siglock, flags);
  90        }
  91
  92        return (bytes > 0);
  93}
  94        
  95static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  96                                 struct autofs_wait_queue *wq,
  97                                 int type)
  98{
  99        union {
 100                struct autofs_packet_hdr hdr;
 101                union autofs_packet_union v4_pkt;
 102                union autofs_v5_packet_union v5_pkt;
 103        } pkt;
 104        struct file *pipe = NULL;
 105        size_t pktsz;
 106
 107        DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 108                (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);
 109
 110        memset(&pkt,0,sizeof pkt); /* For security reasons */
 111
 112        pkt.hdr.proto_version = sbi->version;
 113        pkt.hdr.type = type;
 114        mutex_lock(&sbi->wq_mutex);
 115
 116        /* Check if we have become catatonic */
 117        if (sbi->catatonic) {
 118                mutex_unlock(&sbi->wq_mutex);
 119                return;
 120        }
 121        switch (type) {
 122        /* Kernel protocol v4 missing and expire packets */
 123        case autofs_ptype_missing:
 124        {
 125                struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 126
 127                pktsz = sizeof(*mp);
 128
 129                mp->wait_queue_token = wq->wait_queue_token;
 130                mp->len = wq->name.len;
 131                memcpy(mp->name, wq->name.name, wq->name.len);
 132                mp->name[wq->name.len] = '\0';
 133                break;
 134        }
 135        case autofs_ptype_expire_multi:
 136        {
 137                struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 138
 139                pktsz = sizeof(*ep);
 140
 141                ep->wait_queue_token = wq->wait_queue_token;
 142                ep->len = wq->name.len;
 143                memcpy(ep->name, wq->name.name, wq->name.len);
 144                ep->name[wq->name.len] = '\0';
 145                break;
 146        }
 147        /*
 148         * Kernel protocol v5 packet for handling indirect and direct
 149         * mount missing and expire requests
 150         */
 151        case autofs_ptype_missing_indirect:
 152        case autofs_ptype_expire_indirect:
 153        case autofs_ptype_missing_direct:
 154        case autofs_ptype_expire_direct:
 155        {
 156                struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 157
 158                pktsz = sizeof(*packet);
 159
 160                packet->wait_queue_token = wq->wait_queue_token;
 161                packet->len = wq->name.len;
 162                memcpy(packet->name, wq->name.name, wq->name.len);
 163                packet->name[wq->name.len] = '\0';
 164                packet->dev = wq->dev;
 165                packet->ino = wq->ino;
 166                packet->uid = wq->uid;
 167                packet->gid = wq->gid;
 168                packet->pid = wq->pid;
 169                packet->tgid = wq->tgid;
 170                break;
 171        }
 172        default:
 173                printk("autofs4_notify_daemon: bad type %d!\n", type);
 174                mutex_unlock(&sbi->wq_mutex);
 175                return;
 176        }
 177
 178        pipe = sbi->pipe;
 179        get_file(pipe);
 180
 181        mutex_unlock(&sbi->wq_mutex);
 182
 183        if (autofs4_write(sbi, pipe, &pkt, pktsz))
 184                autofs4_catatonic_mode(sbi);
 185        fput(pipe);
 186}
 187
 188static int autofs4_getpath(struct autofs_sb_info *sbi,
 189                           struct dentry *dentry, char **name)
 190{
 191        struct dentry *root = sbi->sb->s_root;
 192        struct dentry *tmp;
 193        char *buf;
 194        char *p;
 195        int len;
 196        unsigned seq;
 197
 198rename_retry:
 199        buf = *name;
 200        len = 0;
 201
 202        seq = read_seqbegin(&rename_lock);
 203        rcu_read_lock();
 204        spin_lock(&sbi->fs_lock);
 205        for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 206                len += tmp->d_name.len + 1;
 207
 208        if (!len || --len > NAME_MAX) {
 209                spin_unlock(&sbi->fs_lock);
 210                rcu_read_unlock();
 211                if (read_seqretry(&rename_lock, seq))
 212                        goto rename_retry;
 213                return 0;
 214        }
 215
 216        *(buf + len) = '\0';
 217        p = buf + len - dentry->d_name.len;
 218        strncpy(p, dentry->d_name.name, dentry->d_name.len);
 219
 220        for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 221                *(--p) = '/';
 222                p -= tmp->d_name.len;
 223                strncpy(p, tmp->d_name.name, tmp->d_name.len);
 224        }
 225        spin_unlock(&sbi->fs_lock);
 226        rcu_read_unlock();
 227        if (read_seqretry(&rename_lock, seq))
 228                goto rename_retry;
 229
 230        return len;
 231}
 232
 233static struct autofs_wait_queue *
 234autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 235{
 236        struct autofs_wait_queue *wq;
 237
 238        for (wq = sbi->queues; wq; wq = wq->next) {
 239                if (wq->name.hash == qstr->hash &&
 240                    wq->name.len == qstr->len &&
 241                    wq->name.name &&
 242                         !memcmp(wq->name.name, qstr->name, qstr->len))
 243                        break;
 244        }
 245        return wq;
 246}
 247
 248/*
 249 * Check if we have a valid request.
 250 * Returns
 251 * 1 if the request should continue.
 252 *   In this case we can return an autofs_wait_queue entry if one is
 253 *   found or NULL to idicate a new wait needs to be created.
 254 * 0 or a negative errno if the request shouldn't continue.
 255 */
 256static int validate_request(struct autofs_wait_queue **wait,
 257                            struct autofs_sb_info *sbi,
 258                            struct qstr *qstr,
 259                            struct dentry*dentry, enum autofs_notify notify)
 260{
 261        struct autofs_wait_queue *wq;
 262        struct autofs_info *ino;
 263
 264        if (sbi->catatonic)
 265                return -ENOENT;
 266
 267        /* Wait in progress, continue; */
 268        wq = autofs4_find_wait(sbi, qstr);
 269        if (wq) {
 270                *wait = wq;
 271                return 1;
 272        }
 273
 274        *wait = NULL;
 275
 276        /* If we don't yet have any info this is a new request */
 277        ino = autofs4_dentry_ino(dentry);
 278        if (!ino)
 279                return 1;
 280
 281        /*
 282         * If we've been asked to wait on an existing expire (NFY_NONE)
 283         * but there is no wait in the queue ...
 284         */
 285        if (notify == NFY_NONE) {
 286                /*
 287                 * Either we've betean the pending expire to post it's
 288                 * wait or it finished while we waited on the mutex.
 289                 * So we need to wait till either, the wait appears
 290                 * or the expire finishes.
 291                 */
 292
 293                while (ino->flags & AUTOFS_INF_EXPIRING) {
 294                        mutex_unlock(&sbi->wq_mutex);
 295                        schedule_timeout_interruptible(HZ/10);
 296                        if (mutex_lock_interruptible(&sbi->wq_mutex))
 297                                return -EINTR;
 298
 299                        if (sbi->catatonic)
 300                                return -ENOENT;
 301
 302                        wq = autofs4_find_wait(sbi, qstr);
 303                        if (wq) {
 304                                *wait = wq;
 305                                return 1;
 306                        }
 307                }
 308
 309                /*
 310                 * Not ideal but the status has already gone. Of the two
 311                 * cases where we wait on NFY_NONE neither depend on the
 312                 * return status of the wait.
 313                 */
 314                return 0;
 315        }
 316
 317        /*
 318         * If we've been asked to trigger a mount and the request
 319         * completed while we waited on the mutex ...
 320         */
 321        if (notify == NFY_MOUNT) {
 322                struct dentry *new = NULL;
 323                int valid = 1;
 324
 325                /*
 326                 * If the dentry was successfully mounted while we slept
 327                 * on the wait queue mutex we can return success. If it
 328                 * isn't mounted (doesn't have submounts for the case of
 329                 * a multi-mount with no mount at it's base) we can
 330                 * continue on and create a new request.
 331                 */
 332                if (!IS_ROOT(dentry)) {
 333                        if (dentry->d_inode && d_unhashed(dentry)) {
 334                                struct dentry *parent = dentry->d_parent;
 335                                new = d_lookup(parent, &dentry->d_name);
 336                                if (new)
 337                                        dentry = new;
 338                        }
 339                }
 340                if (have_submounts(dentry))
 341                        valid = 0;
 342
 343                if (new)
 344                        dput(new);
 345                return valid;
 346        }
 347
 348        return 1;
 349}
 350
 351int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 352                enum autofs_notify notify)
 353{
 354        struct autofs_wait_queue *wq;
 355        struct qstr qstr;
 356        char *name;
 357        int status, ret, type;
 358
 359        /* In catatonic mode, we don't wait for nobody */
 360        if (sbi->catatonic)
 361                return -ENOENT;
 362
 363        if (!dentry->d_inode) {
 364                /*
 365                 * A wait for a negative dentry is invalid for certain
 366                 * cases. A direct or offset mount "always" has its mount
 367                 * point directory created and so the request dentry must
 368                 * be positive or the map key doesn't exist. The situation
 369                 * is very similar for indirect mounts except only dentrys
 370                 * in the root of the autofs file system may be negative.
 371                 */
 372                if (autofs_type_trigger(sbi->type))
 373                        return -ENOENT;
 374                else if (!IS_ROOT(dentry->d_parent))
 375                        return -ENOENT;
 376        }
 377
 378        name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 379        if (!name)
 380                return -ENOMEM;
 381
 382        /* If this is a direct mount request create a dummy name */
 383        if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 384                qstr.len = sprintf(name, "%p", dentry);
 385        else {
 386                qstr.len = autofs4_getpath(sbi, dentry, &name);
 387                if (!qstr.len) {
 388                        kfree(name);
 389                        return -ENOENT;
 390                }
 391        }
 392        qstr.name = name;
 393        qstr.hash = full_name_hash(name, qstr.len);
 394
 395        if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 396                kfree(qstr.name);
 397                return -EINTR;
 398        }
 399
 400        ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 401        if (ret <= 0) {
 402                if (ret != -EINTR)
 403                        mutex_unlock(&sbi->wq_mutex);
 404                kfree(qstr.name);
 405                return ret;
 406        }
 407
 408        if (!wq) {
 409                /* Create a new wait queue */
 410                wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 411                if (!wq) {
 412                        kfree(qstr.name);
 413                        mutex_unlock(&sbi->wq_mutex);
 414                        return -ENOMEM;
 415                }
 416
 417                wq->wait_queue_token = autofs4_next_wait_queue;
 418                if (++autofs4_next_wait_queue == 0)
 419                        autofs4_next_wait_queue = 1;
 420                wq->next = sbi->queues;
 421                sbi->queues = wq;
 422                init_waitqueue_head(&wq->queue);
 423                memcpy(&wq->name, &qstr, sizeof(struct qstr));
 424                wq->dev = autofs4_get_dev(sbi);
 425                wq->ino = autofs4_get_ino(sbi);
 426                wq->uid = current_uid();
 427                wq->gid = current_gid();
 428                wq->pid = current->pid;
 429                wq->tgid = current->tgid;
 430                wq->status = -EINTR; /* Status return if interrupted */
 431                wq->wait_ctr = 2;
 432                mutex_unlock(&sbi->wq_mutex);
 433
 434                if (sbi->version < 5) {
 435                        if (notify == NFY_MOUNT)
 436                                type = autofs_ptype_missing;
 437                        else
 438                                type = autofs_ptype_expire_multi;
 439                } else {
 440                        if (notify == NFY_MOUNT)
 441                                type = autofs_type_trigger(sbi->type) ?
 442                                        autofs_ptype_missing_direct :
 443                                         autofs_ptype_missing_indirect;
 444                        else
 445                                type = autofs_type_trigger(sbi->type) ?
 446                                        autofs_ptype_expire_direct :
 447                                        autofs_ptype_expire_indirect;
 448                }
 449
 450                DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 451                        (unsigned long) wq->wait_queue_token, wq->name.len,
 452                        wq->name.name, notify);
 453
 454                /* autofs4_notify_daemon() may block */
 455                autofs4_notify_daemon(sbi, wq, type);
 456        } else {
 457                wq->wait_ctr++;
 458                mutex_unlock(&sbi->wq_mutex);
 459                kfree(qstr.name);
 460                DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 461                        (unsigned long) wq->wait_queue_token, wq->name.len,
 462                        wq->name.name, notify);
 463        }
 464
 465        /*
 466         * wq->name.name is NULL iff the lock is already released
 467         * or the mount has been made catatonic.
 468         */
 469        if (wq->name.name) {
 470                /* Block all but "shutdown" signals while waiting */
 471                sigset_t oldset;
 472                unsigned long irqflags;
 473
 474                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 475                oldset = current->blocked;
 476                siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 477                recalc_sigpending();
 478                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 479
 480                wait_event_interruptible(wq->queue, wq->name.name == NULL);
 481
 482                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 483                current->blocked = oldset;
 484                recalc_sigpending();
 485                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 486        } else {
 487                DPRINTK("skipped sleeping");
 488        }
 489
 490        status = wq->status;
 491
 492        /*
 493         * For direct and offset mounts we need to track the requester's
 494         * uid and gid in the dentry info struct. This is so it can be
 495         * supplied, on request, by the misc device ioctl interface.
 496         * This is needed during daemon resatart when reconnecting
 497         * to existing, active, autofs mounts. The uid and gid (and
 498         * related string values) may be used for macro substitution
 499         * in autofs mount maps.
 500         */
 501        if (!status) {
 502                struct autofs_info *ino;
 503                struct dentry *de = NULL;
 504
 505                /* direct mount or browsable map */
 506                ino = autofs4_dentry_ino(dentry);
 507                if (!ino) {
 508                        /* If not lookup actual dentry used */
 509                        de = d_lookup(dentry->d_parent, &dentry->d_name);
 510                        if (de)
 511                                ino = autofs4_dentry_ino(de);
 512                }
 513
 514                /* Set mount requester */
 515                if (ino) {
 516                        spin_lock(&sbi->fs_lock);
 517                        ino->uid = wq->uid;
 518                        ino->gid = wq->gid;
 519                        spin_unlock(&sbi->fs_lock);
 520                }
 521
 522                if (de)
 523                        dput(de);
 524        }
 525
 526        /* Are we the last process to need status? */
 527        mutex_lock(&sbi->wq_mutex);
 528        if (!--wq->wait_ctr)
 529                kfree(wq);
 530        mutex_unlock(&sbi->wq_mutex);
 531
 532        return status;
 533}
 534
 535
 536int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 537{
 538        struct autofs_wait_queue *wq, **wql;
 539
 540        mutex_lock(&sbi->wq_mutex);
 541        for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 542                if (wq->wait_queue_token == wait_queue_token)
 543                        break;
 544        }
 545
 546        if (!wq) {
 547                mutex_unlock(&sbi->wq_mutex);
 548                return -EINVAL;
 549        }
 550
 551        *wql = wq->next;        /* Unlink from chain */
 552        kfree(wq->name.name);
 553        wq->name.name = NULL;   /* Do not wait on this queue */
 554        wq->status = status;
 555        wake_up_interruptible(&wq->queue);
 556        if (!--wq->wait_ctr)
 557                kfree(wq);
 558        mutex_unlock(&sbi->wq_mutex);
 559
 560        return 0;
 561}
 562
 563
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