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