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	for (;;) {
85		allow_signal(SIGHUP);
86
87		if (!jffs2_thread_should_wake(c)) {
88			set_current_state (TASK_INTERRUPTIBLE);
89			D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
90			/* Yes, there's a race here; we checked jffs2_thread_should_wake()
91			   before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
92			   matter - We don't care if we miss a wakeup, because the GC thread
93			   is only an optimisation anyway. */
94			schedule();
95		}
96
97		if (try_to_freeze())
98			continue;
99
100		/* This thread is purely an optimisation. But if it runs when
101		   other things could be running, it actually makes things a
102		   lot worse. Use yield() and put it at the back of the runqueue
103		   every time. Especially during boot, pulling an inode in
104		   with read_inode() is much preferable to having the GC thread
105		   get there first. */
106		yield();
107
108		/* Put_super will send a SIGKILL and then wait on the sem.
109		 */
110		while (signal_pending(current)) {
111			siginfo_t info;
112			unsigned long signr;
113
114			signr = dequeue_signal_lock(current, &current->blocked, &info);
115
116			switch(signr) {
117			case SIGSTOP:
118				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
119				set_current_state(TASK_STOPPED);
120				schedule();
121				break;
122
123			case SIGKILL:
124				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
125				goto die;
126
127			case SIGHUP:
128				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
129				break;
130			default:
131				D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
132			}
133		}
134		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
135		disallow_signal(SIGHUP);
136
137		D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
138		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
139			printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
140			goto die;
141		}
142	}
143 die:
144	spin_lock(&c->erase_completion_lock);
145	c->gc_task = NULL;
146	spin_unlock(&c->erase_completion_lock);
147	complete_and_exit(&c->gc_thread_exit, 0);
148}
149