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 = get_file(sbi->pipe);
 179
 180        mutex_unlock(&sbi->wq_mutex);
 181
 182        if (autofs4_write(sbi, pipe, &pkt, pktsz))
 183                autofs4_catatonic_mode(sbi);
 184        fput(pipe);
 185}
 186
 187static int autofs4_getpath(struct autofs_sb_info *sbi,
 188                           struct dentry *dentry, char **name)
 189{
 190        struct dentry *root = sbi->sb->s_root;
 191        struct dentry *tmp;
 192        char *buf;
 193        char *p;
 194        int len;
 195        unsigned seq;
 196
 197rename_retry:
 198        buf = *name;
 199        len = 0;
 200
 201        seq = read_seqbegin(&rename_lock);
 202        rcu_read_lock();
 203        spin_lock(&sbi->fs_lock);
 204        for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 205                len += tmp->d_name.len + 1;
 206
 207        if (!len || --len > NAME_MAX) {
 208                spin_unlock(&sbi->fs_lock);
 209                rcu_read_unlock();
 210                if (read_seqretry(&rename_lock, seq))
 211                        goto rename_retry;
 212                return 0;
 213        }
 214
 215        *(buf + len) = '\0';
 216        p = buf + len - dentry->d_name.len;
 217        strncpy(p, dentry->d_name.name, dentry->d_name.len);
 218
 219        for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 220                *(--p) = '/';
 221                p -= tmp->d_name.len;
 222                strncpy(p, tmp->d_name.name, tmp->d_name.len);
 223        }
 224        spin_unlock(&sbi->fs_lock);
 225        rcu_read_unlock();
 226        if (read_seqretry(&rename_lock, seq))
 227                goto rename_retry;
 228
 229        return len;
 230}
 231
 232static struct autofs_wait_queue *
 233autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 234{
 235        struct autofs_wait_queue *wq;
 236
 237        for (wq = sbi->queues; wq; wq = wq->next) {
 238                if (wq->name.hash == qstr->hash &&
 239                    wq->name.len == qstr->len &&
 240                    wq->name.name &&
 241                         !memcmp(wq->name.name, qstr->name, qstr->len))
 242                        break;
 243        }
 244        return wq;
 245}
 246
 247/*
 248 * Check if we have a valid request.
 249 * Returns
 250 * 1 if the request should continue.
 251 *   In this case we can return an autofs_wait_queue entry if one is
 252 *   found or NULL to idicate a new wait needs to be created.
 253 * 0 or a negative errno if the request shouldn't continue.
 254 */
 255static int validate_request(struct autofs_wait_queue **wait,
 256                            struct autofs_sb_info *sbi,
 257                            struct qstr *qstr,
 258                            struct dentry*dentry, enum autofs_notify notify)
 259{
 260        struct autofs_wait_queue *wq;
 261        struct autofs_info *ino;
 262
 263        if (sbi->catatonic)
 264                return -ENOENT;
 265
 266        /* Wait in progress, continue; */
 267        wq = autofs4_find_wait(sbi, qstr);
 268        if (wq) {
 269                *wait = wq;
 270                return 1;
 271        }
 272
 273        *wait = NULL;
 274
 275        /* If we don't yet have any info this is a new request */
 276        ino = autofs4_dentry_ino(dentry);
 277        if (!ino)
 278                return 1;
 279
 280        /*
 281         * If we've been asked to wait on an existing expire (NFY_NONE)
 282         * but there is no wait in the queue ...
 283         */
 284        if (notify == NFY_NONE) {
 285                /*
 286                 * Either we've betean the pending expire to post it's
 287                 * wait or it finished while we waited on the mutex.
 288                 * So we need to wait till either, the wait appears
 289                 * or the expire finishes.
 290                 */
 291
 292                while (ino->flags & AUTOFS_INF_EXPIRING) {
 293                        mutex_unlock(&sbi->wq_mutex);
 294                        schedule_timeout_interruptible(HZ/10);
 295                        if (mutex_lock_interruptible(&sbi->wq_mutex))
 296                                return -EINTR;
 297
 298                        if (sbi->catatonic)
 299                                return -ENOENT;
 300
 301                        wq = autofs4_find_wait(sbi, qstr);
 302                        if (wq) {
 303                                *wait = wq;
 304                                return 1;
 305                        }
 306                }
 307
 308                /*
 309                 * Not ideal but the status has already gone. Of the two
 310                 * cases where we wait on NFY_NONE neither depend on the
 311                 * return status of the wait.
 312                 */
 313                return 0;
 314        }
 315
 316        /*
 317         * If we've been asked to trigger a mount and the request
 318         * completed while we waited on the mutex ...
 319         */
 320        if (notify == NFY_MOUNT) {
 321                struct dentry *new = NULL;
 322                int valid = 1;
 323
 324                /*
 325                 * If the dentry was successfully mounted while we slept
 326                 * on the wait queue mutex we can return success. If it
 327                 * isn't mounted (doesn't have submounts for the case of
 328                 * a multi-mount with no mount at it's base) we can
 329                 * continue on and create a new request.
 330                 */
 331                if (!IS_ROOT(dentry)) {
 332                        if (dentry->d_inode && d_unhashed(dentry)) {
 333                                struct dentry *parent = dentry->d_parent;
 334                                new = d_lookup(parent, &dentry->d_name);
 335                                if (new)
 336                                        dentry = new;
 337                        }
 338                }
 339                if (have_submounts(dentry))
 340                        valid = 0;
 341
 342                if (new)
 343                        dput(new);
 344                return valid;
 345        }
 346
 347        return 1;
 348}
 349
 350int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 351                enum autofs_notify notify)
 352{
 353        struct autofs_wait_queue *wq;
 354        struct qstr qstr;
 355        char *name;
 356        int status, ret, type;
 357
 358        /* In catatonic mode, we don't wait for nobody */
 359        if (sbi->catatonic)
 360                return -ENOENT;
 361
 362        if (!dentry->d_inode) {
 363                /*
 364                 * A wait for a negative dentry is invalid for certain
 365                 * cases. A direct or offset mount "always" has its mount
 366                 * point directory created and so the request dentry must
 367                 * be positive or the map key doesn't exist. The situation
 368                 * is very similar for indirect mounts except only dentrys
 369                 * in the root of the autofs file system may be negative.
 370                 */
 371                if (autofs_type_trigger(sbi->type))
 372                        return -ENOENT;
 373                else if (!IS_ROOT(dentry->d_parent))
 374                        return -ENOENT;
 375        }
 376
 377        name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 378        if (!name)
 379                return -ENOMEM;
 380
 381        /* If this is a direct mount request create a dummy name */
 382        if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 383                qstr.len = sprintf(name, "%p", dentry);
 384        else {
 385                qstr.len = autofs4_getpath(sbi, dentry, &name);
 386                if (!qstr.len) {
 387                        kfree(name);
 388                        return -ENOENT;
 389                }
 390        }
 391        qstr.name = name;
 392        qstr.hash = full_name_hash(name, qstr.len);
 393
 394        if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 395                kfree(qstr.name);
 396                return -EINTR;
 397        }
 398
 399        ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 400        if (ret <= 0) {
 401                if (ret != -EINTR)
 402                        mutex_unlock(&sbi->wq_mutex);
 403                kfree(qstr.name);
 404                return ret;
 405        }
 406
 407        if (!wq) {
 408                /* Create a new wait queue */
 409                wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 410                if (!wq) {
 411                        kfree(qstr.name);
 412                        mutex_unlock(&sbi->wq_mutex);
 413                        return -ENOMEM;
 414                }
 415
 416                wq->wait_queue_token = autofs4_next_wait_queue;
 417                if (++autofs4_next_wait_queue == 0)
 418                        autofs4_next_wait_queue = 1;
 419                wq->next = sbi->queues;
 420                sbi->queues = wq;
 421                init_waitqueue_head(&wq->queue);
 422                memcpy(&wq->name, &qstr, sizeof(struct qstr));
 423                wq->dev = autofs4_get_dev(sbi);
 424                wq->ino = autofs4_get_ino(sbi);
 425                wq->uid = current_uid();
 426                wq->gid = current_gid();
 427                wq->pid = current->pid;
 428                wq->tgid = current->tgid;
 429                wq->status = -EINTR; /* Status return if interrupted */
 430                wq->wait_ctr = 2;
 431                mutex_unlock(&sbi->wq_mutex);
 432
 433                if (sbi->version < 5) {
 434                        if (notify == NFY_MOUNT)
 435                                type = autofs_ptype_missing;
 436                        else
 437                                type = autofs_ptype_expire_multi;
 438                } else {
 439                        if (notify == NFY_MOUNT)
 440                                type = autofs_type_trigger(sbi->type) ?
 441                                        autofs_ptype_missing_direct :
 442                                         autofs_ptype_missing_indirect;
 443                        else
 444                                type = autofs_type_trigger(sbi->type) ?
 445                                        autofs_ptype_expire_direct :
 446                                        autofs_ptype_expire_indirect;
 447                }
 448
 449                DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 450                        (unsigned long) wq->wait_queue_token, wq->name.len,
 451                        wq->name.name, notify);
 452
 453                /* autofs4_notify_daemon() may block */
 454                autofs4_notify_daemon(sbi, wq, type);
 455        } else {
 456                wq->wait_ctr++;
 457                mutex_unlock(&sbi->wq_mutex);
 458                kfree(qstr.name);
 459                DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 460                        (unsigned long) wq->wait_queue_token, wq->name.len,
 461                        wq->name.name, notify);
 462        }
 463
 464        /*
 465         * wq->name.name is NULL iff the lock is already released
 466         * or the mount has been made catatonic.
 467         */
 468        if (wq->name.name) {
 469                /* Block all but "shutdown" signals while waiting */
 470                sigset_t oldset;
 471                unsigned long irqflags;
 472
 473                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 474                oldset = current->blocked;
 475                siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 476                recalc_sigpending();
 477                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 478
 479                wait_event_interruptible(wq->queue, wq->name.name == NULL);
 480
 481                spin_lock_irqsave(&current->sighand->siglock, irqflags);
 482                current->blocked = oldset;
 483                recalc_sigpending();
 484                spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 485        } else {
 486                DPRINTK("skipped sleeping");
 487        }
 488
 489        status = wq->status;
 490
 491        /*
 492         * For direct and offset mounts we need to track the requester's
 493         * uid and gid in the dentry info struct. This is so it can be
 494         * supplied, on request, by the misc device ioctl interface.
 495         * This is needed during daemon resatart when reconnecting
 496         * to existing, active, autofs mounts. The uid and gid (and
 497         * related string values) may be used for macro substitution
 498         * in autofs mount maps.
 499         */
 500        if (!status) {
 501                struct autofs_info *ino;
 502                struct dentry *de = NULL;
 503
 504                /* direct mount or browsable map */
 505                ino = autofs4_dentry_ino(dentry);
 506                if (!ino) {
 507                        /* If not lookup actual dentry used */
 508                        de = d_lookup(dentry->d_parent, &dentry->d_name);
 509                        if (de)
 510                                ino = autofs4_dentry_ino(de);
 511                }
 512
 513                /* Set mount requester */
 514                if (ino) {
 515                        spin_lock(&sbi->fs_lock);
 516                        ino->uid = wq->uid;
 517                        ino->gid = wq->gid;
 518                        spin_unlock(&sbi->fs_lock);
 519                }
 520
 521                if (de)
 522                        dput(de);
 523        }
 524
 525        /* Are we the last process to need status? */
 526        mutex_lock(&sbi->wq_mutex);
 527        if (!--wq->wait_ctr)
 528                kfree(wq);
 529        mutex_unlock(&sbi->wq_mutex);
 530
 531        return status;
 532}
 533
 534
 535int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 536{
 537        struct autofs_wait_queue *wq, **wql;
 538
 539        mutex_lock(&sbi->wq_mutex);
 540        for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 541                if (wq->wait_queue_token == wait_queue_token)
 542                        break;
 543        }
 544
 545        if (!wq) {
 546                mutex_unlock(&sbi->wq_mutex);
 547                return -EINVAL;
 548        }
 549
 550        *wql = wq->next;        /* Unlink from chain */
 551        kfree(wq->name.name);
 552        wq->name.name = NULL;   /* Do not wait on this queue */
 553        wq->status = status;
 554        wake_up_interruptible(&wq->queue);
 555        if (!--wq->wait_ctr)
 556                kfree(wq);
 557        mutex_unlock(&sbi->wq_mutex);
 558
 559        return 0;
 560}
 561
 562
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