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 D1(printk(KERN_DEBUG "JFFS2: Garbage collect thread is pid %d\n", tsk->pid)); 51 wait_for_completion(&c->gc_thread_start); 52 ret = tsk->pid; 53 } 54 55 return ret; 56 } 57 58 void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c) 59 { 60 int wait = 0; 61 spin_lock(&c->erase_completion_lock); 62 if (c->gc_task) { 63 D1(printk(KERN_DEBUG "jffs2: Killing GC task %d\n", c->gc_task->pid)); 64 send_sig(SIGKILL, c->gc_task, 1); 65 wait = 1; 66 } 67 spin_unlock(&c->erase_completion_lock); 68 if (wait) 69 wait_for_completion(&c->gc_thread_exit); 70 } 71 72 static int jffs2_garbage_collect_thread(void *_c) 73 { 74 struct jffs2_sb_info *c = _c; 75 76 allow_signal(SIGKILL); 77 allow_signal(SIGSTOP); 78 allow_signal(SIGCONT); 79 80 c->gc_task = current; 81 complete(&c->gc_thread_start); 82 83 set_user_nice(current, 10); 84 85 set_freezable(); 86 for (;;) { 87 allow_signal(SIGHUP); 88 again: 89 spin_lock(&c->erase_completion_lock); 90 if (!jffs2_thread_should_wake(c)) { 91 set_current_state (TASK_INTERRUPTIBLE); 92 spin_unlock(&c->erase_completion_lock); 93 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread sleeping...\n")); 94 schedule(); 95 } else 96 spin_unlock(&c->erase_completion_lock); 97 98 99 /* Problem - immediately after bootup, the GCD spends a lot 100 * of time in places like jffs2_kill_fragtree(); so much so 101 * that userspace processes (like gdm and X) are starved 102 * despite plenty of cond_resched()s and renicing. Yield() 103 * doesn't help, either (presumably because userspace and GCD 104 * are generally competing for a higher latency resource - 105 * disk). 106 * This forces the GCD to slow the hell down. Pulling an 107 * inode in with read_inode() is much preferable to having 108 * the GC thread get there first. */ 109 schedule_timeout_interruptible(msecs_to_jiffies(50)); 110 111 if (kthread_should_stop()) { 112 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): kthread_stop() called.\n")); 113 goto die; 114 } 115 116 /* Put_super will send a SIGKILL and then wait on the sem. 117 */ 118 while (signal_pending(current) || freezing(current)) { 119 siginfo_t info; 120 unsigned long signr; 121 122 if (try_to_freeze()) 123 goto again; 124 125 signr = dequeue_signal_lock(current, ¤t->blocked, &info); 126 127 switch(signr) { 128 case SIGSTOP: 129 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGSTOP received.\n")); 130 set_current_state(TASK_STOPPED); 131 schedule(); 132 break; 133 134 case SIGKILL: 135 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGKILL received.\n")); 136 goto die; 137 138 case SIGHUP: 139 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): SIGHUP received.\n")); 140 break; 141 default: 142 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): signal %ld received\n", signr)); 143 } 144 } 145 /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */ 146 disallow_signal(SIGHUP); 147 148 D1(printk(KERN_DEBUG "jffs2_garbage_collect_thread(): pass\n")); 149 if (jffs2_garbage_collect_pass(c) == -ENOSPC) { 150 printk(KERN_NOTICE "No space for garbage collection. Aborting GC thread\n"); 151 goto die; 152 } 153 } 154 die: 155 spin_lock(&c->erase_completion_lock); 156 c->gc_task = NULL; 157 spin_unlock(&c->erase_completion_lock); 158 complete_and_exit(&c->gc_thread_exit, 0); 159 } 160