release/src-rt-6.x.4708/linux/linux-2.6.36/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 #include <linux/kernel.h>
  14 #include <linux/jffs2.h>
  15 #include <linux/mtd/mtd.h>
  16 #include <linux/completion.h>
  17 #include <linux/sched.h>
  18 #include <linux/freezer.h>
  19 #include <linux/kthread.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         assert_spin_locked(&c->erase_completion_lock);
  28         if (c->gc_task && jffs2_thread_should_wake(c))
  29                 send_sig(SIGHUP, c->gc_task, 1);
  30 }
  31
  32 /* This must only ever be called when no GC thread is currently running */
  33 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
  34 {
  35         struct task_struct *tsk;
  36         int ret = 0;
  37
  38         BUG_ON(c->gc_task);
  39
  40         init_completion(&c->gc_thread_start);
  41         init_completion(&c->gc_thread_exit);
  42
  43         tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
  44         if (IS_ERR(tsk)) {
  45                 printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %ld\n", -PTR_ERR(tsk));
  46                 complete(&c->gc_thread_exit);
  47                 ret = PTR_ERR(tsk);
  48         } else {
  49                 /* Wait for it... */
  50                 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", tsk->pid));
  51                 wait_for_completion(&c->gc_thread_start);
  52                 ret = tsk->pid;
  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         allow_signal(SIGKILL);
  77         allow_signal(SIGSTOP);
  78         allow_signal(SIGCONT);
  79
  80         c->gc_task = current;
  81         complete(&c->gc_thread_start);
  82
  83         set_user_nice(current, 10);
  84
  85         set_freezable();
  86         for (;;) {
  87                 allow_signal(SIGHUP);
  88         again:
  89                 spin_lock(&c->erase_completion_lock);
  90                 if (!jffs2_thread_should_wake(c)) {
  91                         set_current_state (TASK_INTERRUPTIBLE);
  92                         spin_unlock(&c->erase_completion_lock);
  93                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
  94                         schedule();
  95                 } else
  96                         spin_unlock(&c->erase_completion_lock);
  97
  98
  99                 /* Problem - immediately after bootup, the GCD spends a lot
 100                  * of time in places like jffs2_kill_fragtree(); so much so
 101                  * that userspace processes (like gdm and X) are starved
 102                  * despite plenty of cond_resched()s and renicing.  Yield()
 103                  * doesn't help, either (presumably because userspace and GCD
 104                  * are generally competing for a higher latency resource -
 105                  * disk).
 106                  * This forces the GCD to slow the hell down.   Pulling an
 107                  * inode in with read_inode() is much preferable to having
 108                  * the GC thread get there first. */
 109                 schedule_timeout_interruptible(msecs_to_jiffies(50));
 110
 111                 if (kthread_should_stop()) {
 112                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread():  kthread_stop() called.\n"));
 113                         goto die;
 114                 }
 115
 116                 /* Put_super will send a SIGKILL and then wait on the sem.
 117                  */
 118                 while (signal_pending(current) || freezing(current)) {
 119                         siginfo_t info;
 120                         unsigned long signr;
 121
 122                         if (try_to_freeze())
 123                                 goto again;
 124
 125                         signr = dequeue_signal_lock(current, &current->blocked, &info);
 126
 127                         switch(signr) {
 128                         case SIGSTOP:
 129                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
 130                                 set_current_state(TASK_STOPPED);
 131                                 schedule();
 132                                 break;
 133
 134                         case SIGKILL:
 135                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
 136                                 goto die;
 137
 138                         case SIGHUP:
 139                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
 140                                 break;
 141                         default:
 142                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
 143                         }
 144                 }
 145                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
 146                 disallow_signal(SIGHUP);
 147
 148                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
 149                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 150                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
 151                         goto die;
 152                 }
 153         }
 154  die:
 155         spin_lock(&c->erase_completion_lock);
 156         c->gc_task = NULL;
 157         spin_unlock(&c->erase_completion_lock);
 158         complete_and_exit(&c->gc_thread_exit, 0);
 159 }