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                kfree(wq->name.name);
  46                wq->name.name = NULL;
  47                wq->wait_ctr--;
  48                wake_up_interruptible(&wq->queue);
  49                wq = nwq;
  50        }
  51        fput(sbi->pipe);        /* Close the pipe */
  52        sbi->pipe = NULL;
  53        sbi->pipefd = -1;
  54        mutex_unlock(&sbi->wq_mutex);
  55}
  56
  57static int autofs4_write(struct autofs_sb_info *sbi,
  58                         struct file *file, const void *addr, int bytes)
  59{
  60        unsigned long sigpipe, flags;
  61        mm_segment_t fs;
  62        const char *data = (const char *)addr;
  63        ssize_t wr = 0;
  64
  65        sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  66
  67        /* Save pointer to user space and point back to kernel space */
  68        fs = get_fs();
  69        set_fs(KERNEL_DS);
  70
  71        mutex_lock(&sbi->pipe_mutex);
  72        while (bytes &&
  73               (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
  74                data += wr;
  75                bytes -= wr;
  76        }
  77        mutex_unlock(&sbi->pipe_mutex);
  78
  79        set_fs(fs);
  80
  81        /* Keep the currently executing process from receiving a
  82           SIGPIPE unless it was already supposed to get one */
  83        if (wr == -EPIPE && !sigpipe) {
  84                spin_lock_irqsave(&current->sighand->siglock, flags);
  85                sigdelset(&current->pending.signal, SIGPIPE);
  86                recalc_sigpending();
  87                spin_unlock_irqrestore(&current->sighand->siglock, flags);
  88        }
  89
  90        return (bytes > 0);
  91}
  92        
  93static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  94                                 struct autofs_wait_queue *wq,
  95                                 int type)
  96{
  97        union {
  98                struct autofs_packet_hdr hdr;
  99                union autofs_packet_union v4_pkt;
 100                union autofs_v5_packet_union v5_pkt;
 101        } pkt;
 102        struct file *pipe = NULL;
 103        size_t pktsz;
 104
 105        DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 106                (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);
 107
 108        memset(&pkt,0,sizeof pkt); /* For security reasons */
 109
 110        pkt.hdr.proto_version = sbi->version;
 111        pkt.hdr.type = type;
 112        mutex_lock(&sbi->wq_mutex);
 113
 114        /* Check if we have become catatonic */
 115        if (sbi->catatonic) {
 116                mutex_unlock(&sbi->wq_mutex);
 117                return;
 118        }
 119        switch (type) {
 120        /* Kernel protocol v4 missing and expire packets */
 121        case autofs_ptype_missing:
 122        {
 123                struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 124
 125                pktsz = sizeof(*mp);
 126
 127                mp->wait_queue_token = wq->wait_queue_token;
 128                mp->len = wq->name.len;
 129                memcpy(mp->name, wq->name.name, wq->name.len);
 130                mp->name[wq->name.len] = '\0';
 131                break;
 132        }
 133        case autofs_ptype_expire_multi:
 134        {
 135                struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;
 136
 137                pktsz = sizeof(*ep);
 138
 139                ep->wait_queue_token = wq->wait_queue_token;
 140                ep->len = wq->name.len;
 141                memcpy(ep->name, wq->name.name, wq->name.len);
 142                ep->name[wq->name.len] = '\0';
 143                break;
 144        }
 145        /*
 146         * Kernel protocol v5 packet for handling indirect and direct
 147         * mount missing and expire requests
 148         */
 149        case autofs_ptype_missing_indirect:
 150        case autofs_ptype_expire_indirect:
 151        case autofs_ptype_missing_direct:
 152        case autofs_ptype_expire_direct:
 153        {
 154                struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 155                struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 156
 157                pktsz = sizeof(*packet);
 158
 159                packet->wait_queue_token = wq->wait_queue_token;
 160                packet->len = wq->name.len;
 161                memcpy(packet->name, wq->name.name, wq->name.len);
 162                packet->name[wq->name.len] = '\0';
 163                packet->dev = wq->dev;
 164                packet->ino = wq->ino;
 165                packet->uid = from_kuid_munged(user_ns, wq->uid);
 166                packet->gid = from_kgid_munged(user_ns, wq->gid);
 167                packet->pid = wq->pid;
 168                packet->tgid = wq->tgid;
 169                break;
 170        }
 171        default:
 172                printk("autofs4_notify_daemon: bad type %d!\n", type);
 173                mutex_unlock(&sbi->wq_mutex);
 174                return;
 175        }
 176
 177        pipe = get_file(sbi->pipe);
 178
 179        mutex_unlock(&sbi->wq_mutex);
 180
 181        if (autofs4_write(sbi, pipe, &pkt, pktsz))
 182                autofs4_catatonic_mode(sbi);
 183        fput(pipe);
 184}
 185
 186static int autofs4_getpath(struct autofs_sb_info *sbi,
 187                           struct dentry *dentry, char **name)
 188{
 189        struct dentry *root = sbi->sb->s_root;
 190        struct dentry *tmp;
 191        char *buf;
 192        char *p;
 193        int len;
 194        unsigned seq;
 195
 196rename_retry:
 197        buf = *name;
 198        len = 0;
 199
 200        seq = read_seqbegin(&rename_lock);
 201        rcu_read_lock();
 202        spin_lock(&sbi->fs_lock);
 203        for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 204                len += tmp->d_name.len + 1;
 205
 206        if (!len || --len > NAME_MAX) {
 207                spin_unlock(&sbi->fs_lock);
 208                rcu_read_unlock();
 209                if (read_seqretry(&rename_lock, seq))
 210                        goto rename_retry;
 211                return 0;
 212        }
 213
 214        *(buf + len) = '\0';
 215        p = buf + len - dentry->d_name.len;
 216        strncpy(p, dentry->d_name.name, dentry->d_name.len);
 217
 218        for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 219                *(--p) = '/';
 220                p -= tmp->d_name.len;
 221                strncpy(p, tmp->d_name.name, tmp->d_name.len);
 222        }
 223        spin_unlock(&sbi->fs_lock);
 224        rcu_read_unlock();
 225        if (read_seqretry(&rename_lock, seq))
 226                goto rename_retry;
 227
 228        return len;
 229}
 230
 231static struct autofs_wait_queue *
 232autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 233{
 234        struct autofs_wait_queue *wq;
 235
 236        for (wq = sbi->queues; wq; wq = wq->next) {
 237                if (wq->name.hash == qstr->hash &&
 238                    wq->name.len == qstr->len &&
 239                    wq->name.name &&
 240                         !memcmp(wq->name.name, qstr->name, qstr->len))
 241                        break;
 242        }
 243        return wq;
 244}
 245
 246/*
 247 * Check if we have a valid request.
 248 * Returns
 249 * 1 if the request should continue.
 250 *   In this case we can return an autofs_wait_queue entry if one is
 251 *   found or NULL to idicate a new wait needs to be created.
 252 * 0 or a negative errno if the request shouldn't continue.
 253 */
 254static int validate_request(struct autofs_wait_queue **wait,
 255                            struct autofs_sb_info *sbi,
 256                            struct qstr *qstr,
 257                            struct dentry*dentry, enum autofs_notify notify)
 258{
 259        struct autofs_wait_queue *wq;
 260        struct autofs_info *ino;
 261
 262        if (sbi->catatonic)
 263                return -ENOENT;
 264
 265        /* Wait in progress, continue; */
 266        wq = autofs4_find_wait(sbi, qstr);
 267        if (wq) {
 268                *wait = wq;
 269                return 1;
 270        }
 271
 272        *wait = NULL;
 273
 274        /* If we don't yet have any info this is a new request */
 275        ino = autofs4_dentry_ino(dentry);
 276        if (!ino)
 277                return 1;
 278
 279        /*
 280         * If we've been asked to wait on an existing expire (NFY_NONE)
 281         * but there is no wait in the queue ...
 282         */
 283        if (notify == NFY_NONE) {
 284                /*
 285                 * Either we've betean the pending expire to post it's
 286                 * wait or it finished while we waited on the mutex.
 287                 * So we need to wait till either, the wait appears
 288                 * or the expire finishes.
 289                 */
 290
 291                while (ino->flags & AUTOFS_INF_EXPIRING) {
 292                        mutex_unlock(&sbi->wq_mutex);
 293                        schedule_timeout_interruptible(HZ/10);
 294                        if (mutex_lock_interruptible(&sbi->wq_mutex))
 295                                return -EINTR;
 296
 297                        if (sbi->catatonic)
 298                                return -ENOENT;
 299
 300                        wq = autofs4_find_wait(sbi, qstr);
 301                        if (wq) {
 302                                *wait = wq;
 303                                return 1;
 304                        }
 305                }
 306
 307                /*
 308                 * Not ideal but the status has already gone. Of the two
 309                 * cases where we wait on NFY_NONE neither depend on the
 310                 * return status of the wait.
 311                 */
 312                return 0;
 313        }
 314
 315        /*
 316         * If we've been asked to trigger a mount and the request
 317         * completed while we waited on the mutex ...
 318         */
 319        if (notify == NFY_MOUNT) {
 320                struct dentry *new = NULL;
 321                int valid = 1;
 322
 323                /*
 324                 * If the dentry was successfully mounted while we slept
 325                 * on the wait queue mutex we can return success. If it
 326                 * isn't mounted (doesn't have submounts for the case of
 327                 * a multi-mount with no mount at it's base) we can
 328                 * continue on and create a new request.
 329                 */
 330                if (!IS_ROOT(dentry)) {
 331                        if (dentry->d_inode && d_unhashed(dentry)) {
 332                                struct dentry *parent = dentry->d_parent;
 333                                new = d_lookup(parent, &dentry->d_name);
 334                                if (new)
 335                                        dentry = new;
 336                        }
 337                }
 338                if (have_submounts(dentry))
 339                        valid = 0;
 340
 341                if (new)
 342                        dput(new);
 343                return valid;
 344        }
 345
 346        return 1;
 347}
 348
 349int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 350                enum autofs_notify notify)
 351{
 352        struct autofs_wait_queue *wq;
 353        struct qstr qstr;
 354        char *name;
 355        int status, ret, type;
 356
 357        /* In catatonic mode, we don't wait for nobody */
 358        if (sbi->catatonic)
 359                return -ENOENT;
 360
 361        if (!dentry->d_inode) {
 362                /*
 363                 * A wait for a negative dentry is invalid for certain
 364                 * cases. A direct or offset mount "always" has its mount
 365                 * point directory created and so the request dentry must
 366                 * be positive or the map key doesn't exist. The situation
 367                 * is very similar for indirect mounts except only dentrys
 368                 * in the root of the autofs file system may be negative.
 369                 */
 370                if (autofs_type_trigger(sbi->type))
 371                        return -ENOENT;
 372                else if (!IS_ROOT(dentry->d_parent))
 373                        return -ENOENT;
 374        }
 375
 376        name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 377        if (!name)
 378                return -ENOMEM;
 379
 380        /* If this is a direct mount request create a dummy name */
 381        if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 382                qstr.len = sprintf(name, "%p", dentry);
 383        else {
 384                qstr.len = autofs4_getpath(sbi, dentry, &name);
 385                if (!qstr.len) {
 386                        kfree(name);
 387                        return -ENOENT;
 388                }
 389        }
 390        qstr.name = name;
 391        qstr.hash = full_name_hash(name, qstr.len);
 392
 393        if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 394                kfree(qstr.name);
 395                return -EINTR;
 396        }
 397
 398        ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 399        if (ret <= 0) {
 400                if (ret != -EINTR)
 401                        mutex_unlock(&sbi->wq_mutex);
 402                kfree(qstr.name);
 403                return ret;
 404        }
 405
 406        if (!wq) {
 407                /* Create a new wait queue */
 408                wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 409                if (!wq) {
 410                        kfree(qstr.name);
 411                        mutex_unlock(&sbi->wq_mutex);
 412                        return -ENOMEM;
 413                }
 414
 415                wq->wait_queue_token = autofs4_next_wait_queue;
 416                if (++autofs4_next_wait_queue == 0)
 417                        autofs4_next_wait_queue = 1;
 418                wq->next = sbi->queues;
 419                sbi->queues = wq;
 420                init_waitqueue_head(&wq->queue);
 421                memcpy(&wq->name, &qstr, sizeof(struct qstr));
 422                wq->dev = autofs4_get_dev(sbi);
 423                wq->ino = autofs4_get_ino(sbi);
 424                wq->uid = current_uid();
 425                wq->gid = current_gid();
 426                wq->pid = current->pid;
 427                wq->tgid = current->tgid;
 428                wq->status = -EINTR; /* Status return if interrupted */
 429                wq->wait_ctr = 2;
 430                mutex_unlock(&sbi->wq_mutex);
 431
 432                if (sbi->version < 5) {
 433                        if (notify == NFY_MOUNT)
 434                                type = autofs_ptype_missing;
 435                        else
 436                                type = autofs_ptype_expire_multi;
 437                } else {
 438                        if (notify == NFY_MOUNT)
 439                                type = autofs_type_trigger(sbi->type) ?
 440                                        autofs_ptype_missing_direct :
 441                                         autofs_ptype_missing_indirect;
 442                        else
 443                                type = autofs_type_trigger(sbi->type) ?
 444                                        autofs_ptype_expire_direct :
 445                                        autofs_ptype_expire_indirect;
 446                }
 447
 448                DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 449                        (unsigned long) wq->wait_queue_token, wq->name.len,
 450                        wq->name.name, notify);
 451
 452                /* autofs4_notify_daemon() may block */
 453                autofs4_notify_daemon(sbi, wq, type);
 454        } else {
 455                wq->wait_ctr++;
 456                mutex_unlock(&sbi->wq_mutex);
 457                kfree(qstr.name);
 458                DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 459                        (unsigned long) wq->wait_queue_token, wq->name.len,
 460                        wq->name.name, notify);
 461        }
 462
 463        /*
 464         * wq->name.name is NULL iff the lock is already released
 465         * or the mount has been made catatonic.
 466         */
 467        if (wq->name.name) {
 468                /* Block all but "shutdown" signals while waiting */
 469                sigset_t oldset;
 470                unsigned long irqflags;
 471
 472                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 473                oldset = current->blocked;
 474                siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 475                recalc_sigpending();
 476                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 477
 478                wait_event_interruptible(wq->queue, wq->name.name == NULL);
 479
 480                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 481                current->blocked = oldset;
 482                recalc_sigpending();
 483                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 484        } else {
 485                DPRINTK("skipped sleeping");
 486        }
 487
 488        status = wq->status;
 489
 490        /*
 491         * For direct and offset mounts we need to track the requester's
 492         * uid and gid in the dentry info struct. This is so it can be
 493         * supplied, on request, by the misc device ioctl interface.
 494         * This is needed during daemon resatart when reconnecting
 495         * to existing, active, autofs mounts. The uid and gid (and
 496         * related string values) may be used for macro substitution
 497         * in autofs mount maps.
 498         */
 499        if (!status) {
 500                struct autofs_info *ino;
 501                struct dentry *de = NULL;
 502
 503                /* direct mount or browsable map */
 504                ino = autofs4_dentry_ino(dentry);
 505                if (!ino) {
 506                        /* If not lookup actual dentry used */
 507                        de = d_lookup(dentry->d_parent, &dentry->d_name);
 508                        if (de)
 509                                ino = autofs4_dentry_ino(de);
 510                }
 511
 512                /* Set mount requester */
 513                if (ino) {
 514                        spin_lock(&sbi->fs_lock);
 515                        ino->uid = wq->uid;
 516                        ino->gid = wq->gid;
 517                        spin_unlock(&sbi->fs_lock);
 518                }
 519
 520                if (de)
 521                        dput(de);
 522        }
 523
 524        /* Are we the last process to need status? */
 525        mutex_lock(&sbi->wq_mutex);
 526        if (!--wq->wait_ctr)
 527                kfree(wq);
 528        mutex_unlock(&sbi->wq_mutex);
 529
 530        return status;
 531}
 532
 533
 534int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 535{
 536        struct autofs_wait_queue *wq, **wql;
 537
 538        mutex_lock(&sbi->wq_mutex);
 539        for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 540                if (wq->wait_queue_token == wait_queue_token)
 541                        break;
 542        }
 543
 544        if (!wq) {
 545                mutex_unlock(&sbi->wq_mutex);
 546                return -EINVAL;
 547        }
 548
 549        *wql = wq->next;        /* Unlink from chain */
 550        kfree(wq->name.name);
 551        wq->name.name = NULL;   /* Do not wait on this queue */
 552        wq->status = status;
 553        wake_up_interruptible(&wq->queue);
 554        if (!--wq->wait_ctr)
 555                kfree(wq);
 556        mutex_unlock(&sbi->wq_mutex);
 557
 558        return 0;
 559}
 560
 561
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