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, ¤t->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 } 167