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
25 static int jffs2_garbage_collect_thread(void *);
26
jffs2_garbage_collect_trigger(struct jffs2_sb_info * c)27 void 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 */
jffs2_start_garbage_collect_thread(struct jffs2_sb_info * c)35 int 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
jffs2_stop_garbage_collect_thread(struct jffs2_sb_info * c)61 void 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
jffs2_garbage_collect_thread(void * _c)75 static 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