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 jffs2_dbg(1, "JFFS2: Garbage collect thread is pid %d\n", 51 tsk->pid); 52 wait_for_completion(&c->gc_thread_start); 53 ret = tsk->pid; 54 } 55 56 return ret; 57 } 58 59 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c) 60 { 61 int wait = 0; 62 spin_lock(&c->erase_completion_lock); 63 if (c->gc_task) { 64 jffs2_dbg(1, "jffs2: Killing GC task %d\n", c->gc_task->pid); 65 send_sig(SIGKILL, c->gc_task, 1); 66 wait = 1; 67 } 68 spin_unlock(&c->erase_completion_lock); 69 if (wait) 70 wait_for_completion(&c->gc_thread_exit); 71 } 72 73 static int jffs2_garbage_collect_thread(void *_c) 74 { 75 struct jffs2_sb_info *c = _c; 76 77 allow_signal(SIGKILL); 78 allow_signal(SIGSTOP); 79 allow_signal(SIGCONT); 80 81 c->gc_task = current; 82 complete(&c->gc_thread_start); 83 84 set_user_nice(current, 10); 85 86 set_freezable(); 87 for (;;) { 88 allow_signal(SIGHUP); 89 again: 90 spin_lock(&c->erase_completion_lock); 91 if (!jffs2_thread_should_wake(c)) { 92 set_current_state (TASK_INTERRUPTIBLE); 93 spin_unlock(&c->erase_completion_lock); 94 jffs2_dbg(1, "%s(): sleeping...\n", __func__); 95 schedule(); 96 } else 97 spin_unlock(&c->erase_completion_lock); 98 99 100 /* Problem - immediately after bootup, the GCD spends a lot 101 * of time in places like jffs2_kill_fragtree(); so much so 102 * that userspace processes (like gdm and X) are starved 103 * despite plenty of cond_resched()s and renicing. Yield() 104 * doesn't help, either (presumably because userspace and GCD 105 * are generally competing for a higher latency resource - 106 * disk). 107 * This forces the GCD to slow the hell down. Pulling an 108 * inode in with read_inode() is much preferable to having 109 * the GC thread get there first. */ 110 schedule_timeout_interruptible(msecs_to_jiffies(50)); 111 112 if (kthread_should_stop()) { 113 jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__); 114 goto die; 115 } 116 117 /* Put_super will send a SIGKILL and then wait on the sem. 118 */ 119 while (signal_pending(current) || freezing(current)) { 120 siginfo_t info; 121 unsigned long signr; 122 123 if (try_to_freeze()) 124 goto again; 125 126 signr = dequeue_signal_lock(current, ¤t->blocked, &info); 127 128 switch(signr) { 129 case SIGSTOP: 130 jffs2_dbg(1, "%s(): SIGSTOP received\n", 131 __func__); 132 set_current_state(TASK_STOPPED); 133 schedule(); 134 break; 135 136 case SIGKILL: 137 jffs2_dbg(1, "%s(): SIGKILL received\n", 138 __func__); 139 goto die; 140 141 case SIGHUP: 142 jffs2_dbg(1, "%s(): SIGHUP received\n", 143 __func__); 144 break; 145 default: 146 jffs2_dbg(1, "%s(): signal %ld received\n", 147 __func__, signr); 148 } 149 } 150 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */ 151 disallow_signal(SIGHUP); 152 153 jffs2_dbg(1, "%s(): pass\n", __func__); 154 if (jffs2_garbage_collect_pass(c) == -ENOSPC) { 155 printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n"); 156 goto die; 157 } 158 } 159 die: 160 spin_lock(&c->erase_completion_lock); 161 c->gc_task = NULL; 162 spin_unlock(&c->erase_completion_lock); 163 complete_and_exit(&c->gc_thread_exit, 0); 164 } 165