root/fs/jffs2/background.c

DEFINITIONS

1. jffs2_garbage_collect_trigger
2. jffs2_start_garbage_collect_thread
3. jffs2_stop_garbage_collect_thread
4. jffs2_garbage_collect_thread

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 *
 * Created by David Woodhouse <dwmw2@infradead.org>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#include <linux/kernel.h>
#include <linux/jffs2.h>
#include <linux/mtd/mtd.h>
#include <linux/completion.h>
#include <linux/sched.h>
#include <linux/freezer.h>
#include "nodelist.h"


static int jffs2_garbage_collect_thread(void *);

void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
{
        spin_lock(&c->erase_completion_lock);
        if (c->gc_task && jffs2_thread_should_wake(c))
                send_sig(SIGHUP, c->gc_task, 1);
        spin_unlock(&c->erase_completion_lock);
}

/* This must only ever be called when no GC thread is currently running */
int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
{
        pid_t pid;
        int ret = 0;

        BUG_ON(c->gc_task);

        init_completion(&c->gc_thread_start);
        init_completion(&c->gc_thread_exit);

        pid = kernel_thread(jffs2_garbage_collect_thread, c, CLONE_FS|CLONE_FILES);
        if (pid < 0) {
                printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %d\n", -pid);
                complete(&c->gc_thread_exit);
                ret = pid;
        } else {
                /* Wait for it... */
                D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", pid));
                wait_for_completion(&c->gc_thread_start);
        }

        return ret;
}

void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
{
        int wait = 0;
        spin_lock(&c->erase_completion_lock);
        if (c->gc_task) {
                D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid));
                send_sig(SIGKILL, c->gc_task, 1);
                wait = 1;
        }
        spin_unlock(&c->erase_completion_lock);
        if (wait)
                wait_for_completion(&c->gc_thread_exit);
}

static int jffs2_garbage_collect_thread(void *_c)
{
        struct jffs2_sb_info *c = _c;

        daemonize("jffs2_gcd_mtd%d", c->mtd->index);
        allow_signal(SIGKILL);
        allow_signal(SIGSTOP);
        allow_signal(SIGCONT);

        c->gc_task = current;
        complete(&c->gc_thread_start);

        set_user_nice(current, 10);

        set_freezable();
        for (;;) {
                allow_signal(SIGHUP);
        again:
                if (!jffs2_thread_should_wake(c)) {
                        set_current_state (TASK_INTERRUPTIBLE);
                        D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
                        /* Yes, there's a race here; we checked jffs2_thread_should_wake()
                           before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
                           matter - We don't care if we miss a wakeup, because the GC thread
                           is only an optimisation anyway. */
                        schedule();
                }

                /* This thread is purely an optimisation. But if it runs when
                   other things could be running, it actually makes things a
                   lot worse. Use yield() and put it at the back of the runqueue
                   every time. Especially during boot, pulling an inode in
                   with read_inode() is much preferable to having the GC thread
                   get there first. */
                yield();

                /* Put_super will send a SIGKILL and then wait on the sem.
                 */
                while (signal_pending(current) || freezing(current)) {
                        siginfo_t info;
                        unsigned long signr;

                        if (try_to_freeze())
                                goto again;

                        signr = dequeue_signal_lock(current, &current->blocked, &info);

                        switch(signr) {
                        case SIGSTOP:
                                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
                                set_current_state(TASK_STOPPED);
                                schedule();
                                break;

                        case SIGKILL:
                                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
                                goto die;

                        case SIGHUP:
                                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
                                break;
                        default:
                                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
                        }
                }
                /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
                disallow_signal(SIGHUP);

                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
                if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
                        printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
                        goto die;
                }
        }
 die:
        spin_lock(&c->erase_completion_lock);
        c->gc_task = NULL;
        spin_unlock(&c->erase_completion_lock);
        complete_and_exit(&c->gc_thread_exit, 0);
}