v4.19.13 snapshot.
diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
new file mode 100644
index 0000000..453a6a1
--- /dev/null
+++ b/fs/jffs2/background.c
@@ -0,0 +1,165 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/jffs2.h>
+#include <linux/mtd/mtd.h>
+#include <linux/completion.h>
+#include <linux/sched/signal.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include "nodelist.h"
+
+
+static int jffs2_garbage_collect_thread(void *);
+
+void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
+{
+ assert_spin_locked(&c->erase_completion_lock);
+ if (c->gc_task && jffs2_thread_should_wake(c))
+ send_sig(SIGHUP, c->gc_task, 1);
+}
+
+/* This must only ever be called when no GC thread is currently running */
+int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
+{
+ struct task_struct *tsk;
+ int ret = 0;
+
+ BUG_ON(c->gc_task);
+
+ init_completion(&c->gc_thread_start);
+ init_completion(&c->gc_thread_exit);
+
+ tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
+ if (IS_ERR(tsk)) {
+ pr_warn("fork failed for JFFS2 garbage collect thread: %ld\n",
+ -PTR_ERR(tsk));
+ complete(&c->gc_thread_exit);
+ ret = PTR_ERR(tsk);
+ } else {
+ /* Wait for it... */
+ jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);
+ wait_for_completion(&c->gc_thread_start);
+ ret = tsk->pid;
+ }
+
+ return ret;
+}
+
+void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
+{
+ int wait = 0;
+ spin_lock(&c->erase_completion_lock);
+ if (c->gc_task) {
+ jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);
+ send_sig(SIGKILL, c->gc_task, 1);
+ wait = 1;
+ }
+ spin_unlock(&c->erase_completion_lock);
+ if (wait)
+ wait_for_completion(&c->gc_thread_exit);
+}
+
+static int jffs2_garbage_collect_thread(void *_c)
+{
+ struct jffs2_sb_info *c = _c;
+ sigset_t hupmask;
+
+ siginitset(&hupmask, sigmask(SIGHUP));
+ allow_signal(SIGKILL);
+ allow_signal(SIGSTOP);
+ allow_signal(SIGHUP);
+
+ c->gc_task = current;
+ complete(&c->gc_thread_start);
+
+ set_user_nice(current, 10);
+
+ set_freezable();
+ for (;;) {
+ sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
+ again:
+ spin_lock(&c->erase_completion_lock);
+ if (!jffs2_thread_should_wake(c)) {
+ set_current_state (TASK_INTERRUPTIBLE);
+ spin_unlock(&c->erase_completion_lock);
+ jffs2_dbg(1, "%s(): sleeping...\n", __func__);
+ schedule();
+ } else {
+ spin_unlock(&c->erase_completion_lock);
+ }
+ /* Problem - immediately after bootup, the GCD spends a lot
+ * of time in places like jffs2_kill_fragtree(); so much so
+ * that userspace processes (like gdm and X) are starved
+ * despite plenty of cond_resched()s and renicing. Yield()
+ * doesn't help, either (presumably because userspace and GCD
+ * are generally competing for a higher latency resource -
+ * disk).
+ * This forces the GCD to slow the hell down. Pulling an
+ * inode in with read_inode() is much preferable to having
+ * the GC thread get there first. */
+ schedule_timeout_interruptible(msecs_to_jiffies(50));
+
+ if (kthread_should_stop()) {
+ jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
+ goto die;
+ }
+
+ /* Put_super will send a SIGKILL and then wait on the sem.
+ */
+ while (signal_pending(current) || freezing(current)) {
+ unsigned long signr;
+
+ if (try_to_freeze())
+ goto again;
+
+ signr = kernel_dequeue_signal(NULL);
+
+ switch(signr) {
+ case SIGSTOP:
+ jffs2_dbg(1, "%s(): SIGSTOP received\n",
+ __func__);
+ kernel_signal_stop();
+ break;
+
+ case SIGKILL:
+ jffs2_dbg(1, "%s(): SIGKILL received\n",
+ __func__);
+ goto die;
+
+ case SIGHUP:
+ jffs2_dbg(1, "%s(): SIGHUP received\n",
+ __func__);
+ break;
+ default:
+ jffs2_dbg(1, "%s(): signal %ld received\n",
+ __func__, signr);
+ }
+ }
+ /* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
+ sigprocmask(SIG_BLOCK, &hupmask, NULL);
+
+ jffs2_dbg(1, "%s(): pass\n", __func__);
+ if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
+ pr_notice("No space for garbage collection. Aborting GC thread\n");
+ goto die;
+ }
+ }
+ die:
+ spin_lock(&c->erase_completion_lock);
+ c->gc_task = NULL;
+ spin_unlock(&c->erase_completion_lock);
+ complete_and_exit(&c->gc_thread_exit, 0);
+}