/* -*- c -*- --------------------------------------------------------------- *
 *
 * linux/fs/autofs/waitq.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
 *
 * 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 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;

        /** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/

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

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

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

        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",
                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;
        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);
                return;
        }

        /* Check if we have become catatonic */
        mutex_lock(&sbi->wq_mutex);
        if (!sbi->catatonic) {
                pipe = sbi->pipe;
                get_file(pipe);
        }
        mutex_unlock(&sbi->wq_mutex);

        if (pipe) {
                if (autofs4_write(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;

        /* 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;

                        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 == 0)
                        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;
}