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                 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                 /* Put_super will send a SIGKILL and then wait on the sem.
 111                  */
 112                 while (signal_pending(current) || freezing(current)) {
 113                         siginfo_t info;
 114                         unsigned long signr;
 115
 116                         if (try_to_freeze())
 117                                 goto again;
 118
 119                         signr = dequeue_signal_lock(current, &current->blocked, &info);
 120
 121                         switch(signr) {
 122                         case SIGSTOP:
 123                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n"));
 124                                 set_current_state(TASK_STOPPED);
 125                                 schedule();
 126                                 break;
 127
 128                         case SIGKILL:
 129                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n"));
 130                                 goto die;
 131
 132                         case SIGHUP:
 133                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n"));
 134                                 break;
 135                         default:
 136                                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr));
 137                         }
 138                 }
 139                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
 140                 disallow_signal(SIGHUP);
 141
 142                 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n"));
 143                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 144                         printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n");
 145                         goto die;
 146                 }
 147         }
 148  die:
 149         spin_lock(&c->erase_completion_lock);
 150         c->gc_task = NULL;
 151         spin_unlock(&c->erase_completion_lock);
 152         complete_and_exit(&c->gc_thread_exit, 0);
 153 }