1/*
2 * JFFS2 -- Journalling Flash File System, Version 2.
3 *
4 * Copyright © 2001-2007 Red Hat, Inc.
5 * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
6 *
7 * Created by David Woodhouse <dwmw2@infradead.org>
8 *
9 * For licensing information, see the file 'LICENCE' in this directory.
10 *
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/kernel.h>
16#include <linux/jffs2.h>
17#include <linux/mtd/mtd.h>
18#include <linux/completion.h>
19#include <linux/sched.h>
20#include <linux/freezer.h>
21#include <linux/kthread.h>
22#include "nodelist.h"
23
24
25static int jffs2_garbage_collect_thread(void *);
26
27void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
28{
29	assert_spin_locked(&c->erase_completion_lock);
30	if (c->gc_task && jffs2_thread_should_wake(c))
31		send_sig(SIGHUP, c->gc_task, 1);
32}
33
34/* This must only ever be called when no GC thread is currently running */
35int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
36{
37	struct task_struct *tsk;
38	int ret = 0;
39
40	BUG_ON(c->gc_task);
41
42	init_completion(&c->gc_thread_start);
43	init_completion(&c->gc_thread_exit);
44
45	tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
46	if (IS_ERR(tsk)) {
47		pr_warn("fork failed for JFFS2 garbage collect thread: %ld\n",
48			-PTR_ERR(tsk));
49		complete(&c->gc_thread_exit);
50		ret = PTR_ERR(tsk);
51	} else {
52		/* Wait for it... */
53		jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);
54		wait_for_completion(&c->gc_thread_start);
55		ret = tsk->pid;
56	}
57
58	return ret;
59}
60
61void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
62{
63	int wait = 0;
64	spin_lock(&c->erase_completion_lock);
65	if (c->gc_task) {
66		jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);
67		send_sig(SIGKILL, c->gc_task, 1);
68		wait = 1;
69	}
70	spin_unlock(&c->erase_completion_lock);
71	if (wait)
72		wait_for_completion(&c->gc_thread_exit);
73}
74
75static int jffs2_garbage_collect_thread(void *_c)
76{
77	struct jffs2_sb_info *c = _c;
78	sigset_t hupmask;
79
80	siginitset(&hupmask, sigmask(SIGHUP));
81	allow_signal(SIGKILL);
82	allow_signal(SIGSTOP);
83	allow_signal(SIGCONT);
84	allow_signal(SIGHUP);
85
86	c->gc_task = current;
87	complete(&c->gc_thread_start);
88
89	set_user_nice(current, 10);
90
91	set_freezable();
92	for (;;) {
93		sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
94	again:
95		spin_lock(&c->erase_completion_lock);
96		if (!jffs2_thread_should_wake(c)) {
97			set_current_state (TASK_INTERRUPTIBLE);
98			spin_unlock(&c->erase_completion_lock);
99			jffs2_dbg(1, "%s(): sleeping...\n", __func__);
100			schedule();
101		} else {
102			spin_unlock(&c->erase_completion_lock);
103		}
104		/* Problem - immediately after bootup, the GCD spends a lot
105		 * of time in places like jffs2_kill_fragtree(); so much so
106		 * that userspace processes (like gdm and X) are starved
107		 * despite plenty of cond_resched()s and renicing.  Yield()
108		 * doesn't help, either (presumably because userspace and GCD
109		 * are generally competing for a higher latency resource -
110		 * disk).
111		 * This forces the GCD to slow the hell down.   Pulling an
112		 * inode in with read_inode() is much preferable to having
113		 * the GC thread get there first. */
114		schedule_timeout_interruptible(msecs_to_jiffies(50));
115
116		if (kthread_should_stop()) {
117			jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
118			goto die;
119		}
120
121		/* Put_super will send a SIGKILL and then wait on the sem.
122		 */
123		while (signal_pending(current) || freezing(current)) {
124			siginfo_t info;
125			unsigned long signr;
126
127			if (try_to_freeze())
128				goto again;
129
130			signr = dequeue_signal_lock(current, &current->blocked, &info);
131
132			switch(signr) {
133			case SIGSTOP:
134				jffs2_dbg(1, "%s(): SIGSTOP received\n",
135					  __func__);
136				set_current_state(TASK_STOPPED);
137				schedule();
138				break;
139
140			case SIGKILL:
141				jffs2_dbg(1, "%s(): SIGKILL received\n",
142					  __func__);
143				goto die;
144
145			case SIGHUP:
146				jffs2_dbg(1, "%s(): SIGHUP received\n",
147					  __func__);
148				break;
149			default:
150				jffs2_dbg(1, "%s(): signal %ld received\n",
151					  __func__, signr);
152			}
153		}
154		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
155		sigprocmask(SIG_BLOCK, &hupmask, NULL);
156
157		jffs2_dbg(1, "%s(): pass\n", __func__);
158		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
159			pr_notice("No space for garbage collection. Aborting GC thread\n");
160			goto die;
161		}
162	}
163 die:
164	spin_lock(&c->erase_completion_lock);
165	c->gc_task = NULL;
166	spin_unlock(&c->erase_completion_lock);
167	complete_and_exit(&c->gc_thread_exit, 0);
168}
169