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 <linux/kthread.h>
  19 #include "nodelist.h"
  20
  21
  22 static int jffs2_garbage_collect_thread(void *);
  23
  24 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
  25 {
  26         assert_spin_locked(&c->erase_completion_lock);
  27         if (c->gc_task && jffs2_thread_should_wake(c))
  28                 send_sig(SIGHUP, c->gc_task, 1);
  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         struct task_struct *tsk;
  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         tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
  43         if (IS_ERR(tsk)) {
  44                 printk(KERN_WARNING "fork failed for JFFS2 garbage collect thread: %ld\n", -PTR_ERR(tsk));
  45                 complete(&c->gc_thread_exit);
  46                 ret = PTR_ERR(tsk);
  47         } else {
  48                 /* Wait for it... */
  49                 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", tsk->pid));
  50                 wait_for_completion(&c->gc_thread_start);
  51                 ret = tsk->pid;
  52         }
  53
  54         return ret;
  55 }
  56
  57 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
  58 {
  59         int wait = 0;
  60         spin_lock(&c->erase_completion_lock);
  61         if (c->gc_task) {
  62                 D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid));
  63                 send_sig(SIGKILL, c->gc_task, 1);
  64                 wait = 1;
  65         }
  66         spin_unlock(&c->erase_completion_lock);
  67         if (wait)
  68                 wait_for_completion(&c->gc_thread_exit);
  69 }
  70
  71 static int jffs2_garbage_collect_thread(void *_c)
  72 {
  73         struct jffs2_sb_info *c = _c;
  74
  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                 spin_lock(&c->erase_completion_lock);
  89                 if (!jffs2_thread_should_wake(c)) {
  90                         set_current_state (TASK_INTERRUPTIBLE);
  91                         spin_unlock(&c->erase_completion_lock);
  92                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n"));
  93                         schedule();
  94                 } else
  95                         spin_unlock(&c->erase_completion_lock);
  96
  97
  98                 /* Problem - immediately after bootup, the GCD spends a lot
  99                  * of time in places like jffs2_kill_fragtree(); so much so
 100                  * that userspace processes (like gdm and X) are starved
 101                  * despite plenty of cond_resched()s and renicing.  Yield()
 102                  * doesn't help, either (presumably because userspace and GCD
 103                  * are generally competing for a higher latency resource -
 104                  * disk).
 105                  * This forces the GCD to slow the hell down.   Pulling an
 106                  * inode in with read_inode() is much preferable to having
 107                  * the GC thread get there first. */
 108                 schedule_timeout_interruptible(msecs_to_jiffies(50));
 109
 110                 if (kthread_should_stop()) {
 111                         D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread():  kthread_stop() called.\n"));
 112                         goto die;
 113                 }
 114
 115                 /* Put_super will send a SIGKILL and then wait on the sem.
 116                  */
 117                 while (signal_pending(current) || freezing(current)) {
 118                         siginfo_t info;
 119                         unsigned long signr;
 120
 121                         if (try_to_freeze())
 122                                 goto again;
 123
 124                         signr = dequeue_signal_lock(current, &current->blocked, &info);
 125
 126                         switch(signr) {
 127                         case SIGSTOP:
 128                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
 129                                 set_current_state(TASK_STOPPED);
 130                                 schedule();
 131                                 break;
 132
 133                         case SIGKILL:
 134                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
 135                                 goto die;
 136
 137                         case SIGHUP:
 138                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
 139                                 break;
 140                         default:
 141                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
 142                         }
 143                 }
 144                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
 145                 disallow_signal(SIGHUP);
 146
 147                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
 148                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 149                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
 150                         goto die;
 151                 }
 152         }
 153  die:
 154         spin_lock(&c->erase_completion_lock);
 155         c->gc_task = NULL;
 156         spin_unlock(&c->erase_completion_lock);
 157         complete_and_exit(&c->gc_thread_exit, 0);
 158 }