[JFFS2] Check for all-zero node headers
[linux-2.6] / fs / jffs2 / background.c
1 /*
2  * JFFS2 -- Journalling Flash File System, Version 2.
3  *
4  * Copyright (C) 2001-2003 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  * $Id: background.c,v 1.54 2005/05/20 21:37:12 gleixner Exp $
11  *
12  */
13
14 #include <linux/kernel.h>
15 #include <linux/jffs2.h>
16 #include <linux/mtd/mtd.h>
17 #include <linux/completion.h>
18 #include <linux/sched.h>
19 #include <linux/freezer.h>
20 #include "nodelist.h"
21
22
23 static int jffs2_garbage_collect_thread(void *);
24
25 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
26 {
27         spin_lock(&c->erase_completion_lock);
28         if (c->gc_task && jffs2_thread_should_wake(c))
29                 send_sig(SIGHUP, c->gc_task, 1);
30         spin_unlock(&c->erase_completion_lock);
31 }
32
33 /* This must only ever be called when no GC thread is currently running */
34 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
35 {
36         pid_t pid;
37         int ret = 0;
38
39         BUG_ON(c->gc_task);
40
41         init_completion(&c->gc_thread_start);
42         init_completion(&c->gc_thread_exit);
43
44         pid = kernel_thread(jffs2_garbage_collect_thread, c, CLONE_FS|CLONE_FILES);
45         if (pid < 0) {
46                 printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %d\n", -pid);
47                 complete(&c->gc_thread_exit);
48                 ret = pid;
49         } else {
50                 /* Wait for it... */
51                 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", pid));
52                 wait_for_completion(&c->gc_thread_start);
53         }
54
55         return ret;
56 }
57
58 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
59 {
60         int wait = 0;
61         spin_lock(&c->erase_completion_lock);
62         if (c->gc_task) {
63                 D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid));
64                 send_sig(SIGKILL, c->gc_task, 1);
65                 wait = 1;
66         }
67         spin_unlock(&c->erase_completion_lock);
68         if (wait)
69                 wait_for_completion(&c->gc_thread_exit);
70 }
71
72 static int jffs2_garbage_collect_thread(void *_c)
73 {
74         struct jffs2_sb_info *c = _c;
75
76         daemonize("jffs2_gcd_mtd%d", c->mtd->index);
77         allow_signal(SIGKILL);
78         allow_signal(SIGSTOP);
79         allow_signal(SIGCONT);
80
81         c->gc_task = current;
82         complete(&c->gc_thread_start);
83
84         set_user_nice(current, 10);
85
86         for (;;) {
87                 allow_signal(SIGHUP);
88
89                 if (!jffs2_thread_should_wake(c)) {
90                         set_current_state (TASK_INTERRUPTIBLE);
91                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
92                         /* Yes, there's a race here; we checked jffs2_thread_should_wake()
93                            before setting current->state to TASK_INTERRUPTIBLE. But it doesn't
94                            matter - We don't care if we miss a wakeup, because the GC thread
95                            is only an optimisation anyway. */
96                         schedule();
97                 }
98
99                 if (try_to_freeze())
100                         continue;
101
102                 /* This thread is purely an optimisation. But if it runs when
103                    other things could be running, it actually makes things a
104                    lot worse. Use yield() and put it at the back of the runqueue
105                    every time. Especially during boot, pulling an inode in
106                    with read_inode() is much preferable to having the GC thread
107                    get there first. */
108                 yield();
109
110                 /* Put_super will send a SIGKILL and then wait on the sem.
111                  */
112                 while (signal_pending(current)) {
113                         siginfo_t info;
114                         unsigned long signr;
115
116                         signr = dequeue_signal_lock(current, &current->blocked, &info);
117
118                         switch(signr) {
119                         case SIGSTOP:
120                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
121                                 set_current_state(TASK_STOPPED);
122                                 schedule();
123                                 break;
124
125                         case SIGKILL:
126                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
127                                 goto die;
128
129                         case SIGHUP:
130                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
131                                 break;
132                         default:
133                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
134                         }
135                 }
136                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
137                 disallow_signal(SIGHUP);
138
139                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
140                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
141                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
142                         goto die;
143                 }
144         }
145  die:
146         spin_lock(&c->erase_completion_lock);
147         c->gc_task = NULL;
148         spin_unlock(&c->erase_completion_lock);
149         complete_and_exit(&c->gc_thread_exit, 0);
150 }