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