GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / jffs2 / background.c
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
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 */
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
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
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(NULL);
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         complete_and_exit(&c->gc_thread_exit, 0);
165 }