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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/kernel.h>
  16 #include <linux/jffs2.h>
  17 #include <linux/mtd/mtd.h>
  18 #include <linux/completion.h>
  19 #include <linux/sched.h>
  20 #include <linux/freezer.h>
  21 #include <linux/kthread.h>
  22 #include "nodelist.h"
  23
  24
  25 static int jffs2_garbage_collect_thread(void *);
  26
  27 void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
  28 {
  29         assert_spin_locked(&c->erase_completion_lock);
  30         if (c->gc_task && jffs2_thread_should_wake(c))
  31                 send_sig(SIGHUP, c->gc_task, 1);
  32 }
  33
  34 /* This must only ever be called when no GC thread is currently running */
  35 int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
  36 {
  37         struct task_struct *tsk;
  38         int ret = 0;
  39
  40         BUG_ON(c->gc_task);
  41
  42         init_completion(&c->gc_thread_start);
  43         init_completion(&c->gc_thread_exit);
  44
  45         tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
  46         if (IS_ERR(tsk)) {
  47                 pr_warn("fork failed for JFFS2 garbage collect thread: %ld\n",
  48                         -PTR_ERR(tsk));
  49                 complete(&c->gc_thread_exit);
  50                 ret = PTR_ERR(tsk);
  51         } else {
  52                 /* Wait for it... */
  53                 jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);
  54                 wait_for_completion(&c->gc_thread_start);
  55                 ret = tsk->pid;
  56         }
  57
  58         return ret;
  59 }
  60
  61 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
  62 {
  63         int wait = 0;
  64         spin_lock(&c->erase_completion_lock);
  65         if (c->gc_task) {
  66                 jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);
  67                 send_sig(SIGKILL, c->gc_task, 1);
  68                 wait = 1;
  69         }
  70         spin_unlock(&c->erase_completion_lock);
  71         if (wait)
  72                 wait_for_completion(&c->gc_thread_exit);
  73 }
  74
  75 static int jffs2_garbage_collect_thread(void *_c)
  76 {
  77         struct jffs2_sb_info *c = _c;
  78
  79         allow_signal(SIGKILL);
  80         allow_signal(SIGSTOP);
  81         allow_signal(SIGCONT);
  82
  83         c->gc_task = current;
  84         complete(&c->gc_thread_start);
  85
  86         set_user_nice(current, 10);
  87
  88         set_freezable();
  89         for (;;) {
  90                 allow_signal(SIGHUP);
  91         again:
  92                 spin_lock(&c->erase_completion_lock);
  93                 if (!jffs2_thread_should_wake(c)) {
  94                         set_current_state (TASK_INTERRUPTIBLE);
  95                         spin_unlock(&c->erase_completion_lock);
  96                         jffs2_dbg(1, "%s(): sleeping...\n", __func__);
  97                         schedule();
  98                 } else
  99                         spin_unlock(&c->erase_completion_lock);
 100
 101
 102                 /* Problem - immediately after bootup, the GCD spends a lot
 103                  * of time in places like jffs2_kill_fragtree(); so much so
 104                  * that userspace processes (like gdm and X) are starved
 105                  * despite plenty of cond_resched()s and renicing.  Yield()
 106                  * doesn't help, either (presumably because userspace and GCD
 107                  * are generally competing for a higher latency resource -
 108                  * disk).
 109                  * This forces the GCD to slow the hell down.   Pulling an
 110                  * inode in with read_inode() is much preferable to having
 111                  * the GC thread get there first. */
 112                 schedule_timeout_interruptible(msecs_to_jiffies(50));
 113
 114                 if (kthread_should_stop()) {
 115                         jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
 116                         goto die;
 117                 }
 118
 119                 /* Put_super will send a SIGKILL and then wait on the sem.
 120                  */
 121                 while (signal_pending(current) || freezing(current)) {
 122                         siginfo_t info;
 123                         unsigned long signr;
 124
 125                         if (try_to_freeze())
 126                                 goto again;
 127
 128                         signr = dequeue_signal_lock(current, &current->blocked, &info);
 129
 130                         switch(signr) {
 131                         case SIGSTOP:
 132                                 jffs2_dbg(1, "%s(): SIGSTOP received\n",
 133                                           __func__);
 134                                 set_current_state(TASK_STOPPED);
 135                                 schedule();
 136                                 break;
 137
 138                         case SIGKILL:
 139                                 jffs2_dbg(1, "%s(): SIGKILL received\n",
 140                                           __func__);
 141                                 goto die;
 142
 143                         case SIGHUP:
 144                                 jffs2_dbg(1, "%s(): SIGHUP received\n",
 145                                           __func__);
 146                                 break;
 147                         default:
 148                                 jffs2_dbg(1, "%s(): signal %ld received\n",
 149                                           __func__, signr);
 150                         }
 151                 }
 152                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
 153                 disallow_signal(SIGHUP);
 154
 155                 jffs2_dbg(1, "%s(): pass\n", __func__);
 156                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
 157                         pr_notice("No space for garbage collection. Aborting GC thread\n");
 158                         goto die;
 159                 }
 160         }
 161  die:
 162         spin_lock(&c->erase_completion_lock);
 163         c->gc_task = NULL;
 164         spin_unlock(&c->erase_completion_lock);
 165         complete_and_exit(&c->gc_thread_exit, 0);
 166 }