waitq.c

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/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/waitq.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 2001-2006 Ian Kent <[email protected]>
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/slab.h>
#include <linux/time.h>
#include <linux/signal.h>
#include <linux/file.h>
#include "autofs_i.h"

/* We make this a static variable rather than a part of the superblock; it
   is better if we don't reassign numbers easily even across filesystems */
static autofs_wqt_t autofs4_next_wait_queue = 1;

/* These are the signals we allow interrupting a pending mount */
#define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))

void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
{
    struct autofs_wait_queue *wq, *nwq;

    mutex_lock(&sbi->wq_mutex);
    if (sbi->catatonic) {
        mutex_unlock(&sbi->wq_mutex);
        return;
    }

    DPRINTK("entering catatonic mode");

    sbi->catatonic = 1;
    wq = sbi->queues;
    sbi->queues = NULL; /* Erase all wait queues */
    while (wq) {
        nwq = wq->next;
        wq->status = -ENOENT; /* Magic is gone - report failure */
        if (wq->name.name) {
            kfree(wq->name.name);
            wq->name.name = NULL;
        }
        wq->wait_ctr--;
        wake_up_interruptible(&wq->queue);
        wq = nwq;
    }
    fput(sbi->pipe);    /* Close the pipe */
    sbi->pipe = NULL;
    sbi->pipefd = -1;
    mutex_unlock(&sbi->wq_mutex);
}

static int autofs4_write(struct autofs_sb_info *sbi,
             struct file *file, const void *addr, int bytes)
{
    unsigned long sigpipe, flags;
    mm_segment_t fs;
    const char *data = (const char *)addr;
    ssize_t wr = 0;

    sigpipe = sigismember(&current->pending.signal, SIGPIPE);

    /* Save pointer to user space and point back to kernel space */
    fs = get_fs();
    set_fs(KERNEL_DS);

    mutex_lock(&sbi->pipe_mutex);
    while (bytes &&
           (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
        data += wr;
        bytes -= wr;
    }
    mutex_unlock(&sbi->pipe_mutex);

    set_fs(fs);

    /* Keep the currently executing process from receiving a
       SIGPIPE unless it was already supposed to get one */
    if (wr == -EPIPE && !sigpipe) {
        spin_lock_irqsave(&current->sighand->siglock, flags);
        sigdelset(&current->pending.signal, SIGPIPE);
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sighand->siglock, flags);
    }

    return (bytes > 0);
}
    
static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
                 struct autofs_wait_queue *wq,
                 int type)
{
    union {
        struct autofs_packet_hdr hdr;
        union autofs_packet_union v4_pkt;
        union autofs_v5_packet_union v5_pkt;
    } pkt;
    struct file *pipe = NULL;
    size_t pktsz;

    DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
        (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);

    memset(&pkt,0,sizeof pkt); /* For security reasons */

    pkt.hdr.proto_version = sbi->version;
    pkt.hdr.type = type;
    mutex_lock(&sbi->wq_mutex);

    /* Check if we have become catatonic */
    if (sbi->catatonic) {
        mutex_unlock(&sbi->wq_mutex);
        return;
    }
    switch (type) {
    /* Kernel protocol v4 missing and expire packets */
    case autofs_ptype_missing:
    {
        struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;

        pktsz = sizeof(*mp);

        mp->wait_queue_token = wq->wait_queue_token;
        mp->len = wq->name.len;
        memcpy(mp->name, wq->name.name, wq->name.len);
        mp->name[wq->name.len] = '\0';
        break;
    }
    case autofs_ptype_expire_multi:
    {
        struct autofs_packet_expire_multi *ep = &pkt.v4_pkt.expire_multi;

        pktsz = sizeof(*ep);

        ep->wait_queue_token = wq->wait_queue_token;
        ep->len = wq->name.len;
        memcpy(ep->name, wq->name.name, wq->name.len);
        ep->name[wq->name.len] = '\0';
        break;
    }
    /*
     * Kernel protocol v5 packet for handling indirect and direct
     * mount missing and expire requests
     */
    case autofs_ptype_missing_indirect:
    case autofs_ptype_expire_indirect:
    case autofs_ptype_missing_direct:
    case autofs_ptype_expire_direct:
    {
        struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;

        pktsz = sizeof(*packet);

        packet->wait_queue_token = wq->wait_queue_token;
        packet->len = wq->name.len;
        memcpy(packet->name, wq->name.name, wq->name.len);
        packet->name[wq->name.len] = '\0';
        packet->dev = wq->dev;
        packet->ino = wq->ino;
        packet->uid = wq->uid;
        packet->gid = wq->gid;
        packet->pid = wq->pid;
        packet->tgid = wq->tgid;
        break;
    }
    default:
        printk("autofs4_notify_daemon: bad type %d!\n", type);
        mutex_unlock(&sbi->wq_mutex);
        return;
    }

    pipe = get_file(sbi->pipe);

    mutex_unlock(&sbi->wq_mutex);

    if (autofs4_write(sbi, pipe, &pkt, pktsz))
        autofs4_catatonic_mode(sbi);
    fput(pipe);
}

static int autofs4_getpath(struct autofs_sb_info *sbi,
               struct dentry *dentry, char **name)
{
    struct dentry *root = sbi->sb->s_root;
    struct dentry *tmp;
    char *buf;
    char *p;
    int len;
    unsigned seq;

rename_retry:
    buf = *name;
    len = 0;

    seq = read_seqbegin(&rename_lock);
    rcu_read_lock();
    spin_lock(&sbi->fs_lock);
    for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
        len += tmp->d_name.len + 1;

    if (!len || --len > NAME_MAX) {
        spin_unlock(&sbi->fs_lock);
        rcu_read_unlock();
        if (read_seqretry(&rename_lock, seq))
            goto rename_retry;
        return 0;
    }

    *(buf + len) = '\0';
    p = buf + len - dentry->d_name.len;
    strncpy(p, dentry->d_name.name, dentry->d_name.len);

    for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
        *(--p) = '/';
        p -= tmp->d_name.len;
        strncpy(p, tmp->d_name.name, tmp->d_name.len);
    }
    spin_unlock(&sbi->fs_lock);
    rcu_read_unlock();
    if (read_seqretry(&rename_lock, seq))
        goto rename_retry;

    return len;
}

static struct autofs_wait_queue *
autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
{
    struct autofs_wait_queue *wq;

    for (wq = sbi->queues; wq; wq = wq->next) {
        if (wq->name.hash == qstr->hash &&
            wq->name.len == qstr->len &&
            wq->name.name &&
             !memcmp(wq->name.name, qstr->name, qstr->len))
            break;
    }
    return wq;
}

/*
 * Check if we have a valid request.
 * Returns
 * 1 if the request should continue.
 *   In this case we can return an autofs_wait_queue entry if one is
 *   found or NULL to idicate a new wait needs to be created.
 * 0 or a negative errno if the request shouldn't continue.
 */
static int validate_request(struct autofs_wait_queue **wait,
                struct autofs_sb_info *sbi,
                struct qstr *qstr,
                struct dentry*dentry, enum autofs_notify notify)
{
    struct autofs_wait_queue *wq;
    struct autofs_info *ino;

    if (sbi->catatonic)
        return -ENOENT;

    /* Wait in progress, continue; */
    wq = autofs4_find_wait(sbi, qstr);
    if (wq) {
        *wait = wq;
        return 1;
    }

    *wait = NULL;

    /* If we don't yet have any info this is a new request */
    ino = autofs4_dentry_ino(dentry);
    if (!ino)
        return 1;

    /*
     * If we've been asked to wait on an existing expire (NFY_NONE)
     * but there is no wait in the queue ...
     */
    if (notify == NFY_NONE) {
        /*
         * Either we've betean the pending expire to post it's
         * wait or it finished while we waited on the mutex.
         * So we need to wait till either, the wait appears
         * or the expire finishes.
         */

        while (ino->flags & AUTOFS_INF_EXPIRING) {
            mutex_unlock(&sbi->wq_mutex);
            schedule_timeout_interruptible(HZ/10);
            if (mutex_lock_interruptible(&sbi->wq_mutex))
                return -EINTR;

            if (sbi->catatonic)
                return -ENOENT;

            wq = autofs4_find_wait(sbi, qstr);
            if (wq) {
                *wait = wq;
                return 1;
            }
        }

        /*
         * Not ideal but the status has already gone. Of the two
         * cases where we wait on NFY_NONE neither depend on the
         * return status of the wait.
         */
        return 0;
    }

    /*
     * If we've been asked to trigger a mount and the request
     * completed while we waited on the mutex ...
     */
    if (notify == NFY_MOUNT) {
        struct dentry *new = NULL;
        int valid = 1;

        /*
         * If the dentry was successfully mounted while we slept
         * on the wait queue mutex we can return success. If it
         * isn't mounted (doesn't have submounts for the case of
         * a multi-mount with no mount at it's base) we can
         * continue on and create a new request.
         */
        if (!IS_ROOT(dentry)) {
            if (dentry->d_inode && d_unhashed(dentry)) {
                struct dentry *parent = dentry->d_parent;
                new = d_lookup(parent, &dentry->d_name);
                if (new)
                    dentry = new;
            }
        }
        if (have_submounts(dentry))
            valid = 0;

        if (new)
            dput(new);
        return valid;
    }

    return 1;
}

int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
        enum autofs_notify notify)
{
    struct autofs_wait_queue *wq;
    struct qstr qstr;
    char *name;
    int status, ret, type;

    /* In catatonic mode, we don't wait for nobody */
    if (sbi->catatonic)
        return -ENOENT;

    if (!dentry->d_inode) {
        /*
         * A wait for a negative dentry is invalid for certain
         * cases. A direct or offset mount "always" has its mount
         * point directory created and so the request dentry must
         * be positive or the map key doesn't exist. The situation
         * is very similar for indirect mounts except only dentrys
         * in the root of the autofs file system may be negative.
         */
        if (autofs_type_trigger(sbi->type))
            return -ENOENT;
        else if (!IS_ROOT(dentry->d_parent))
            return -ENOENT;
    }

    name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
    if (!name)
        return -ENOMEM;

    /* If this is a direct mount request create a dummy name */
    if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
        qstr.len = sprintf(name, "%p", dentry);
    else {
        qstr.len = autofs4_getpath(sbi, dentry, &name);
        if (!qstr.len) {
            kfree(name);
            return -ENOENT;
        }
    }
    qstr.name = name;
    qstr.hash = full_name_hash(name, qstr.len);

    if (mutex_lock_interruptible(&sbi->wq_mutex)) {
        kfree(qstr.name);
        return -EINTR;
    }

    ret = validate_request(&wq, sbi, &qstr, dentry, notify);
    if (ret <= 0) {
        if (ret != -EINTR)
            mutex_unlock(&sbi->wq_mutex);
        kfree(qstr.name);
        return ret;
    }

    if (!wq) {
        /* Create a new wait queue */
        wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
        if (!wq) {
            kfree(qstr.name);
            mutex_unlock(&sbi->wq_mutex);
            return -ENOMEM;
        }

        wq->wait_queue_token = autofs4_next_wait_queue;
        if (++autofs4_next_wait_queue == 0)
            autofs4_next_wait_queue = 1;
        wq->next = sbi->queues;
        sbi->queues = wq;
        init_waitqueue_head(&wq->queue);
        memcpy(&wq->name, &qstr, sizeof(struct qstr));
        wq->dev = autofs4_get_dev(sbi);
        wq->ino = autofs4_get_ino(sbi);
        wq->uid = current_uid();
        wq->gid = current_gid();
        wq->pid = current->pid;
        wq->tgid = current->tgid;
        wq->status = -EINTR; /* Status return if interrupted */
        wq->wait_ctr = 2;
        mutex_unlock(&sbi->wq_mutex);

        if (sbi->version < 5) {
            if (notify == NFY_MOUNT)
                type = autofs_ptype_missing;
            else
                type = autofs_ptype_expire_multi;
        } else {
            if (notify == NFY_MOUNT)
                type = autofs_type_trigger(sbi->type) ?
                    autofs_ptype_missing_direct :
                     autofs_ptype_missing_indirect;
            else
                type = autofs_type_trigger(sbi->type) ?
                    autofs_ptype_expire_direct :
                    autofs_ptype_expire_indirect;
        }

        DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
            (unsigned long) wq->wait_queue_token, wq->name.len,
            wq->name.name, notify);

        /* autofs4_notify_daemon() may block */
        autofs4_notify_daemon(sbi, wq, type);
    } else {
        wq->wait_ctr++;
        mutex_unlock(&sbi->wq_mutex);
        kfree(qstr.name);
        DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
            (unsigned long) wq->wait_queue_token, wq->name.len,
            wq->name.name, notify);
    }

    /*
     * wq->name.name is NULL iff the lock is already released
     * or the mount has been made catatonic.
     */
    if (wq->name.name) {
        /* Block all but "shutdown" signals while waiting */
        sigset_t oldset;
        unsigned long irqflags;

        spin_lock_irqsave(&current->sighand->siglock, irqflags);
        oldset = current->blocked;
        siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sighand->siglock, irqflags);

        wait_event_interruptible(wq->queue, wq->name.name == NULL);

        spin_lock_irqsave(&current->sighand->siglock, irqflags);
        current->blocked = oldset;
        recalc_sigpending();
        spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
    } else {
        DPRINTK("skipped sleeping");
    }

    status = wq->status;

    /*
     * For direct and offset mounts we need to track the requester's
     * uid and gid in the dentry info struct. This is so it can be
     * supplied, on request, by the misc device ioctl interface.
     * This is needed during daemon resatart when reconnecting
     * to existing, active, autofs mounts. The uid and gid (and
     * related string values) may be used for macro substitution
     * in autofs mount maps.
     */
    if (!status) {
        struct autofs_info *ino;
        struct dentry *de = NULL;

        /* direct mount or browsable map */
        ino = autofs4_dentry_ino(dentry);
        if (!ino) {
            /* If not lookup actual dentry used */
            de = d_lookup(dentry->d_parent, &dentry->d_name);
            if (de)
                ino = autofs4_dentry_ino(de);
        }

        /* Set mount requester */
        if (ino) {
            spin_lock(&sbi->fs_lock);
            ino->uid = wq->uid;
            ino->gid = wq->gid;
            spin_unlock(&sbi->fs_lock);
        }

        if (de)
            dput(de);
    }

    /* Are we the last process to need status? */
    mutex_lock(&sbi->wq_mutex);
    if (!--wq->wait_ctr)
        kfree(wq);
    mutex_unlock(&sbi->wq_mutex);

    return status;
}


int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
{
    struct autofs_wait_queue *wq, **wql;

    mutex_lock(&sbi->wq_mutex);
    for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
        if (wq->wait_queue_token == wait_queue_token)
            break;
    }

    if (!wq) {
        mutex_unlock(&sbi->wq_mutex);
        return -EINVAL;
    }

    *wql = wq->next;    /* Unlink from chain */
    kfree(wq->name.name);
    wq->name.name = NULL;   /* Do not wait on this queue */
    wq->status = status;
    wake_up_interruptible(&wq->queue);
    if (!--wq->wait_ctr)
        kfree(wq);
    mutex_unlock(&sbi->wq_mutex);

    return 0;
}