Root/fs/jffs2/background.c

1/*
2 * JFFS2 -- Journalling Flash File System, Version 2.
3 *
4 * Copyright © 2001-2007 Red Hat, Inc.
5 *
6 * Created by David Woodhouse <dwmw2@infradead.org>
7 *
8 * For licensing information, see the file 'LICENCE' in this directory.
9 *
10 */
11
12#include <linux/kernel.h>
13#include <linux/jffs2.h>
14#include <linux/mtd/mtd.h>
15#include <linux/completion.h>
16#include <linux/sched.h>
17#include <linux/freezer.h>
18#include "nodelist.h"
19
20
21static int jffs2_garbage_collect_thread(void *);
22
23void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
24{
25    spin_lock(&c->erase_completion_lock);
26    if (c->gc_task && jffs2_thread_should_wake(c))
27        send_sig(SIGHUP, c->gc_task, 1);
28    spin_unlock(&c->erase_completion_lock);
29}
30
31/* This must only ever be called when no GC thread is currently running */
32int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
33{
34    pid_t pid;
35    int ret = 0;
36
37    BUG_ON(c->gc_task);
38
39    init_completion(&c->gc_thread_start);
40    init_completion(&c->gc_thread_exit);
41
42    pid = kernel_thread(jffs2_garbage_collect_thread, c, CLONE_FS|CLONE_FILES);
43    if (pid < 0) {
44        printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %d\n", -pid);
45        complete(&c->gc_thread_exit);
46        ret = pid;
47    } else {
48        /* Wait for it... */
49        D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", pid));
50        wait_for_completion(&c->gc_thread_start);
51    }
52
53    return ret;
54}
55
56void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
57{
58    int wait = 0;
59    spin_lock(&c->erase_completion_lock);
60    if (c->gc_task) {
61        D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid));
62        send_sig(SIGKILL, c->gc_task, 1);
63        wait = 1;
64    }
65    spin_unlock(&c->erase_completion_lock);
66    if (wait)
67        wait_for_completion(&c->gc_thread_exit);
68}
69
70static int jffs2_garbage_collect_thread(void *_c)
71{
72    struct jffs2_sb_info *c = _c;
73
74    daemonize("jffs2_gcd_mtd%d", c->mtd->index);
75    allow_signal(SIGKILL);
76    allow_signal(SIGSTOP);
77    allow_signal(SIGCONT);
78
79    c->gc_task = current;
80    complete(&c->gc_thread_start);
81
82    set_user_nice(current, 10);
83
84    set_freezable();
85    for (;;) {
86        allow_signal(SIGHUP);
87    again:
88        spin_lock(&c->erase_completion_lock);
89        if (!jffs2_thread_should_wake(c)) {
90            set_current_state (TASK_INTERRUPTIBLE);
91            spin_unlock(&c->erase_completion_lock);
92            D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
93            schedule();
94        } else
95            spin_unlock(&c->erase_completion_lock);
96            
97
98        /* Problem - immediately after bootup, the GCD spends a lot
99         * of time in places like jffs2_kill_fragtree(); so much so
100         * that userspace processes (like gdm and X) are starved
101         * despite plenty of cond_resched()s and renicing. Yield()
102         * doesn't help, either (presumably because userspace and GCD
103         * are generally competing for a higher latency resource -
104         * disk).
105         * This forces the GCD to slow the hell down. Pulling an
106         * inode in with read_inode() is much preferable to having
107         * the GC thread get there first. */
108        schedule_timeout_interruptible(msecs_to_jiffies(50));
109
110        /* Put_super will send a SIGKILL and then wait on the sem.
111         */
112        while (signal_pending(current) || freezing(current)) {
113            siginfo_t info;
114            unsigned long signr;
115
116            if (try_to_freeze())
117                goto again;
118
119            signr = dequeue_signal_lock(current, &current->blocked, &info);
120
121            switch(signr) {
122            case SIGSTOP:
123                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
124                set_current_state(TASK_STOPPED);
125                schedule();
126                break;
127
128            case SIGKILL:
129                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
130                goto die;
131
132            case SIGHUP:
133                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
134                break;
135            default:
136                D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
137            }
138        }
139        /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
140        disallow_signal(SIGHUP);
141
142        D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
143        if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
144            printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
145            goto die;
146        }
147    }
148 die:
149    spin_lock(&c->erase_completion_lock);
150    c->gc_task = NULL;
151    spin_unlock(&c->erase_completion_lock);
152    complete_and_exit(&c->gc_thread_exit, 0);
153}
154

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