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TOMOYO Linux Cross Reference
Linux/fs/jffs2/background.c

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  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         sigset_t hupmask;
 79 
 80         siginitset(&hupmask, sigmask(SIGHUP));
 81         allow_signal(SIGKILL);
 82         allow_signal(SIGSTOP);
 83         allow_signal(SIGCONT);
 84         allow_signal(SIGHUP);
 85 
 86         c->gc_task = current;
 87         complete(&c->gc_thread_start);
 88 
 89         set_user_nice(current, 10);
 90 
 91         set_freezable();
 92         for (;;) {
 93                 sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
 94         again:
 95                 spin_lock(&c->erase_completion_lock);
 96                 if (!jffs2_thread_should_wake(c)) {
 97                         set_current_state (TASK_INTERRUPTIBLE);
 98                         spin_unlock(&c->erase_completion_lock);
 99                         jffs2_dbg(1, "%s(): sleeping...\n", __func__);
100                         schedule();
101                 } else {
102                         spin_unlock(&c->erase_completion_lock);
103                 }
104                 /* Problem - immediately after bootup, the GCD spends a lot
105                  * of time in places like jffs2_kill_fragtree(); so much so
106                  * that userspace processes (like gdm and X) are starved
107                  * despite plenty of cond_resched()s and renicing.  Yield()
108                  * doesn't help, either (presumably because userspace and GCD
109                  * are generally competing for a higher latency resource -
110                  * disk).
111                  * This forces the GCD to slow the hell down.   Pulling an
112                  * inode in with read_inode() is much preferable to having
113                  * the GC thread get there first. */
114                 schedule_timeout_interruptible(msecs_to_jiffies(50));
115 
116                 if (kthread_should_stop()) {
117                         jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
118                         goto die;
119                 }
120 
121                 /* Put_super will send a SIGKILL and then wait on the sem.
122                  */
123                 while (signal_pending(current) || freezing(current)) {
124                         siginfo_t info;
125                         unsigned long signr;
126 
127                         if (try_to_freeze())
128                                 goto again;
129 
130                         signr = dequeue_signal_lock(current, &current->blocked, &info);
131 
132                         switch(signr) {
133                         case SIGSTOP:
134                                 jffs2_dbg(1, "%s(): SIGSTOP received\n",
135                                           __func__);
136                                 set_current_state(TASK_STOPPED);
137                                 schedule();
138                                 break;
139 
140                         case SIGKILL:
141                                 jffs2_dbg(1, "%s(): SIGKILL received\n",
142                                           __func__);
143                                 goto die;
144 
145                         case SIGHUP:
146                                 jffs2_dbg(1, "%s(): SIGHUP received\n",
147                                           __func__);
148                                 break;
149                         default:
150                                 jffs2_dbg(1, "%s(): signal %ld received\n",
151                                           __func__, signr);
152                         }
153                 }
154                 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
155                 sigprocmask(SIG_BLOCK, &hupmask, NULL);
156 
157                 jffs2_dbg(1, "%s(): pass\n", __func__);
158                 if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
159                         pr_notice("No space for garbage collection. Aborting GC thread\n");
160                         goto die;
161                 }
162         }
163  die:
164         spin_lock(&c->erase_completion_lock);
165         c->gc_task = NULL;
166         spin_unlock(&c->erase_completion_lock);
167         complete_and_exit(&c->gc_thread_exit, 0);
168 }
169 

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