root/fs/autofs/waitq.c

DEFINITIONS

1. autofs_catatonic_mode
2. autofs_write
3. autofs_notify_daemon
4. autofs_wait
5. autofs_wait_release

/* -*- linux-c -*- --------------------------------------------------------- *
 *
 * linux/fs/autofs/waitq.c
 *
 *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
 *
 * 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 autofs_next_wait_queue = 1;

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

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

        DPRINTK(("autofs: entering catatonic mode\n"));

        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 */
                kfree(wq->name);
                wq->name = NULL;
                wake_up(&wq->queue);
                wq = nwq;
        }
        fput(sbi->pipe);        /* Close the pipe */
        sbi->pipe = NULL;
        autofs_hash_dputall(&sbi->dirhash); /* Remove all dentry pointers */
}

static int autofs_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 autofs_notify_daemon(struct autofs_sb_info *sbi, struct autofs_wait_queue *wq)
{
        struct autofs_packet_missing pkt;

        DPRINTK(("autofs_wait: wait id = 0x%08lx, name = ", wq->wait_queue_token));
        autofs_say(wq->name,wq->len);

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

        pkt.hdr.proto_version = AUTOFS_PROTO_VERSION;
        pkt.hdr.type = autofs_ptype_missing;
        pkt.wait_queue_token = wq->wait_queue_token;
        pkt.len = wq->len;
        memcpy(pkt.name, wq->name, pkt.len);
        pkt.name[pkt.len] = '\0';

        if ( autofs_write(sbi->pipe,&pkt,sizeof(struct autofs_packet_missing)) )
                autofs_catatonic_mode(sbi);
}

int autofs_wait(struct autofs_sb_info *sbi, struct qstr *name)
{
        struct autofs_wait_queue *wq;
        int status;

        /* In catatonic mode, we don't wait for nobody */
        if ( sbi->catatonic )
                return -ENOENT;
        
        /* We shouldn't be able to get here, but just in case */
        if ( name->len > NAME_MAX )
                return -ENOENT;

        for ( wq = sbi->queues ; wq ; wq = wq->next ) {
                if ( wq->hash == name->hash &&
                     wq->len == name->len &&
                     wq->name && !memcmp(wq->name,name->name,name->len) )
                        break;
        }
        
        if ( !wq ) {
                /* Create a new wait queue */
                wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
                if ( !wq )
                        return -ENOMEM;

                wq->name = kmalloc(name->len,GFP_KERNEL);
                if ( !wq->name ) {
                        kfree(wq);
                        return -ENOMEM;
                }
                wq->wait_queue_token = autofs_next_wait_queue++;
                init_waitqueue_head(&wq->queue);
                wq->hash = name->hash;
                wq->len = name->len;
                wq->status = -EINTR; /* Status return if interrupted */
                memcpy(wq->name, name->name, name->len);
                wq->next = sbi->queues;
                sbi->queues = wq;

                /* autofs_notify_daemon() may block */
                wq->wait_ctr = 2;
                autofs_notify_daemon(sbi,wq);
        } else
                wq->wait_ctr++;

        /* wq->name is NULL if and only if the lock is already released */

        if ( sbi->catatonic ) {
                /* We might have slept, so check again for catatonic mode */
                wq->status = -ENOENT;
                kfree(wq->name);
                wq->name = NULL;
        }

        if ( wq->name ) {
                /* Block all but "shutdown" signals while waiting */
                sigset_t sigmask;

                siginitsetinv(&sigmask, SHUTDOWN_SIGS);
                sigprocmask(SIG_BLOCK, &sigmask, &sigmask);

                interruptible_sleep_on(&wq->queue);

                sigprocmask(SIG_SETMASK, &sigmask, NULL);
        } else {
                DPRINTK(("autofs_wait: skipped sleeping\n"));
        }

        status = wq->status;

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

        return status;
}


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

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

        *wql = wq->next;        /* Unlink from chain */
        kfree(wq->name);
        wq->name = NULL;        /* Do not wait on this queue */

        wq->status = status;

        if ( ! --wq->wait_ctr ) /* Is anyone still waiting for this guy? */
                kfree(wq);
        else
                wake_up(&wq->queue);

        return 0;
}