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