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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
[linux-2.6-omap-h63xx.git] / fs / jffs2 / background.c
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
21 static int jffs2_garbage_collect_thread(void *);
22
23 void 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 */
32 int 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
56 void 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
70 static 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         set_freezable();
85         for (;;) {
86                 allow_signal(SIGHUP);
87         again:
88                 if (!jffs2_thread_should_wake(c)) {
89                         set_current_state (TASK_INTERRUPTIBLE);
90                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
91                         /* Yes, there's a race here; we checked jffs2_thread_should_wake()
92                            before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
93                            matter - We don't care if we miss a wakeup, because the GC thread
94                            is only an optimisation anyway. */
95                         schedule();
96                 }
97
98                 /* This thread is purely an optimisation. But if it runs when
99                    other things could be running, it actually makes things a
100                    lot worse. Use yield() and put it at the back of the runqueue
101                    every time. Especially during boot, pulling an inode in
102                    with read_inode() is much preferable to having the GC thread
103                    get there first. */
104                 yield();
105
106                 /* Put_super will send a SIGKILL and then wait on the sem.
107                  */
108                 while (signal_pending(current) || freezing(current)) {
109                         siginfo_t info;
110                         unsigned long signr;
111
112                         if (try_to_freeze())
113                                 goto again;
114
115                         signr = dequeue_signal_lock(current, &current->blocked, &info);
116
117                         switch(signr) {
118                         case SIGSTOP:
119                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
120                                 set_current_state(TASK_STOPPED);
121                                 schedule();
122                                 break;
123
124                         case SIGKILL:
125                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
126                                 goto die;
127
128                         case SIGHUP:
129                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
130                                 break;
131                         default:
132                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
133                         }
134                 }
135                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
136                 disallow_signal(SIGHUP);
137
138                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
139                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
140                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
141                         goto die;
142                 }
143         }
144  die:
145         spin_lock(&c->erase_completion_lock);
146         c->gc_task = NULL;
147         spin_unlock(&c->erase_completion_lock);
148         complete_and_exit(&c->gc_thread_exit, 0);
149 }