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/signal.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(SIGHUP);
84
85	c->gc_task = current;
86	complete(&c->gc_thread_start);
87
88	set_user_nice(current, 10);
89
90	set_freezable();
91	for (;;) {
92		sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
93	again:
94		spin_lock(&c->erase_completion_lock);
95		if (!jffs2_thread_should_wake(c)) {
96			set_current_state (TASK_INTERRUPTIBLE);
97			spin_unlock(&c->erase_completion_lock);
98			jffs2_dbg(1, "%s(): sleeping...\n", __func__);
99			schedule();
100		} else {
101			spin_unlock(&c->erase_completion_lock);
102		}
103		/* Problem - immediately after bootup, the GCD spends a lot
104		 * of time in places like jffs2_kill_fragtree(); so much so
105		 * that userspace processes (like gdm and X) are starved
106		 * despite plenty of cond_resched()s and renicing.  Yield()
107		 * doesn't help, either (presumably because userspace and GCD
108		 * are generally competing for a higher latency resource -
109		 * disk).
110		 * This forces the GCD to slow the hell down.   Pulling an
111		 * inode in with read_inode() is much preferable to having
112		 * the GC thread get there first. */
113		schedule_timeout_interruptible(msecs_to_jiffies(50));
114
115		if (kthread_should_stop()) {
116			jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
117			goto die;
118		}
119
120		/* Put_super will send a SIGKILL and then wait on the sem.
121		 */
122		while (signal_pending(current) || freezing(current)) {
123			unsigned long signr;
124
125			if (try_to_freeze())
126				goto again;
127
128			signr = kernel_dequeue_signal();
129
130			switch(signr) {
131			case SIGSTOP:
132				jffs2_dbg(1, "%s(): SIGSTOP received\n",
133					  __func__);
134				kernel_signal_stop();
135				break;
136
137			case SIGKILL:
138				jffs2_dbg(1, "%s(): SIGKILL received\n",
139					  __func__);
140				goto die;
141
142			case SIGHUP:
143				jffs2_dbg(1, "%s(): SIGHUP received\n",
144					  __func__);
145				break;
146			default:
147				jffs2_dbg(1, "%s(): signal %ld received\n",
148					  __func__, signr);
149			}
150		}
151		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
152		sigprocmask(SIG_BLOCK, &hupmask, NULL);
153
154		jffs2_dbg(1, "%s(): pass\n", __func__);
155		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
156			pr_notice("No space for garbage collection. Aborting GC thread\n");
157			goto die;
158		}
159	}
160 die:
161	spin_lock(&c->erase_completion_lock);
162	c->gc_task = NULL;
163	spin_unlock(&c->erase_completion_lock);
164	kthread_complete_and_exit(&c->gc_thread_exit, 0);
165}
166