--- zzzz-none-000/linux-3.10.107/drivers/md/bcache/closure.h	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/md/bcache/closure.h	2021-02-04 17:41:59.000000000 +0000
@@ -38,7 +38,7 @@
  * they are running owned by the thread that is running them. Otherwise, suppose
  * you submit some bios and wish to have a function run when they all complete:
  *
- * foo_endio(struct bio *bio, int error)
+ * foo_endio(struct bio *bio)
  * {
  *	closure_put(cl);
  * }
@@ -72,30 +72,6 @@
  * closure - _always_ use continue_at(). Doing so consistently will help
  * eliminate an entire class of particularly pernicious races.
  *
- * For a closure to wait on an arbitrary event, we need to introduce waitlists:
- *
- * struct closure_waitlist list;
- * closure_wait_event(list, cl, condition);
- * closure_wake_up(wait_list);
- *
- * These work analagously to wait_event() and wake_up() - except that instead of
- * operating on the current thread (for wait_event()) and lists of threads, they
- * operate on an explicit closure and lists of closures.
- *
- * Because it's a closure we can now wait either synchronously or
- * asynchronously. closure_wait_event() returns the current value of the
- * condition, and if it returned false continue_at() or closure_sync() can be
- * used to wait for it to become true.
- *
- * It's useful for waiting on things when you can't sleep in the context in
- * which you must check the condition (perhaps a spinlock held, or you might be
- * beneath generic_make_request() - in which case you can't sleep on IO).
- *
- * closure_wait_event() will wait either synchronously or asynchronously,
- * depending on whether the closure is in blocking mode or not. You can pick a
- * mode explicitly with closure_wait_event_sync() and
- * closure_wait_event_async(), which do just what you might expect.
- *
  * Lastly, you might have a wait list dedicated to a specific event, and have no
  * need for specifying the condition - you just want to wait until someone runs
  * closure_wake_up() on the appropriate wait list. In that case, just use
@@ -121,55 +97,6 @@
  * All this implies that a closure should typically be embedded in a particular
  * struct (which its refcount will normally control the lifetime of), and that
  * struct can very much be thought of as a stack frame.
- *
- * Locking:
- *
- * Closures are based on work items but they can be thought of as more like
- * threads - in that like threads and unlike work items they have a well
- * defined lifetime; they are created (with closure_init()) and eventually
- * complete after a continue_at(cl, NULL, NULL).
- *
- * Suppose you've got some larger structure with a closure embedded in it that's
- * used for periodically doing garbage collection. You only want one garbage
- * collection happening at a time, so the natural thing to do is protect it with
- * a lock. However, it's difficult to use a lock protecting a closure correctly
- * because the unlock should come after the last continue_to() (additionally, if
- * you're using the closure asynchronously a mutex won't work since a mutex has
- * to be unlocked by the same process that locked it).
- *
- * So to make it less error prone and more efficient, we also have the ability
- * to use closures as locks:
- *
- * closure_init_unlocked();
- * closure_trylock();
- *
- * That's all we need for trylock() - the last closure_put() implicitly unlocks
- * it for you.  But for closure_lock(), we also need a wait list:
- *
- * struct closure_with_waitlist frobnicator_cl;
- *
- * closure_init_unlocked(&frobnicator_cl);
- * closure_lock(&frobnicator_cl);
- *
- * A closure_with_waitlist embeds a closure and a wait list - much like struct
- * delayed_work embeds a work item and a timer_list. The important thing is, use
- * it exactly like you would a regular closure and closure_put() will magically
- * handle everything for you.
- *
- * We've got closures that embed timers, too. They're called, appropriately
- * enough:
- * struct closure_with_timer;
- *
- * This gives you access to closure_delay(). It takes a refcount for a specified
- * number of jiffies - you could then call closure_sync() (for a slightly
- * convoluted version of msleep()) or continue_at() - which gives you the same
- * effect as using a delayed work item, except you can reuse the work_struct
- * already embedded in struct closure.
- *
- * Lastly, there's struct closure_with_waitlist_and_timer. It does what you
- * probably expect, if you happen to need the features of both. (You don't
- * really want to know how all this is implemented, but if I've done my job
- * right you shouldn't have to care).
  */
 
 struct closure;
@@ -179,19 +106,8 @@
 	struct llist_head	list;
 };
 
-enum closure_type {
-	TYPE_closure				= 0,
-	TYPE_closure_with_waitlist		= 1,
-	TYPE_closure_with_timer			= 2,
-	TYPE_closure_with_waitlist_and_timer	= 3,
-	MAX_CLOSURE_TYPE			= 3,
-};
-
 enum closure_state {
 	/*
-	 * CLOSURE_BLOCKING: Causes closure_wait_event() to block, instead of
-	 * waiting asynchronously
-	 *
 	 * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
 	 * the thread that owns the closure, and cleared by the thread that's
 	 * waking up the closure.
@@ -200,10 +116,6 @@
 	 * - indicates that cl->task is valid and closure_put() may wake it up.
 	 * Only set or cleared by the thread that owns the closure.
 	 *
-	 * CLOSURE_TIMER: Analagous to CLOSURE_WAITING, indicates that a closure
-	 * has an outstanding timer. Must be set by the thread that owns the
-	 * closure, and cleared by the timer function when the timer goes off.
-	 *
 	 * The rest are for debugging and don't affect behaviour:
 	 *
 	 * CLOSURE_RUNNING: Set when a closure is running (i.e. by
@@ -218,19 +130,17 @@
 	 * closure with this flag set
 	 */
 
-	CLOSURE_BITS_START	= (1 << 19),
-	CLOSURE_DESTRUCTOR	= (1 << 19),
-	CLOSURE_BLOCKING	= (1 << 21),
-	CLOSURE_WAITING		= (1 << 23),
-	CLOSURE_SLEEPING	= (1 << 25),
-	CLOSURE_TIMER		= (1 << 27),
+	CLOSURE_BITS_START	= (1 << 23),
+	CLOSURE_DESTRUCTOR	= (1 << 23),
+	CLOSURE_WAITING		= (1 << 25),
+	CLOSURE_SLEEPING	= (1 << 27),
 	CLOSURE_RUNNING		= (1 << 29),
 	CLOSURE_STACK		= (1 << 31),
 };
 
 #define CLOSURE_GUARD_MASK					\
-	((CLOSURE_DESTRUCTOR|CLOSURE_BLOCKING|CLOSURE_WAITING|	\
-	  CLOSURE_SLEEPING|CLOSURE_TIMER|CLOSURE_RUNNING|CLOSURE_STACK) << 1)
+	((CLOSURE_DESTRUCTOR|CLOSURE_WAITING|CLOSURE_SLEEPING|	\
+	  CLOSURE_RUNNING|CLOSURE_STACK) << 1)
 
 #define CLOSURE_REMAINING_MASK		(CLOSURE_BITS_START - 1)
 #define CLOSURE_REMAINING_INITIALIZER	(1|CLOSURE_RUNNING)
@@ -250,8 +160,6 @@
 
 	atomic_t		remaining;
 
-	enum closure_type	type;
-
 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 #define CLOSURE_MAGIC_DEAD	0xc054dead
 #define CLOSURE_MAGIC_ALIVE	0xc054a11e
@@ -263,54 +171,12 @@
 #endif
 };
 
-struct closure_with_waitlist {
-	struct closure		cl;
-	struct closure_waitlist	wait;
-};
-
-struct closure_with_timer {
-	struct closure		cl;
-	struct timer_list	timer;
-};
-
-struct closure_with_waitlist_and_timer {
-	struct closure		cl;
-	struct closure_waitlist	wait;
-	struct timer_list	timer;
-};
-
-extern unsigned invalid_closure_type(void);
-
-#define __CLOSURE_TYPE(cl, _t)						\
-	  __builtin_types_compatible_p(typeof(cl), struct _t)		\
-		? TYPE_ ## _t :						\
-
-#define __closure_type(cl)						\
-(									\
-	__CLOSURE_TYPE(cl, closure)					\
-	__CLOSURE_TYPE(cl, closure_with_waitlist)			\
-	__CLOSURE_TYPE(cl, closure_with_timer)				\
-	__CLOSURE_TYPE(cl, closure_with_waitlist_and_timer)		\
-	invalid_closure_type()						\
-)
-
 void closure_sub(struct closure *cl, int v);
 void closure_put(struct closure *cl);
-void closure_queue(struct closure *cl);
 void __closure_wake_up(struct closure_waitlist *list);
 bool closure_wait(struct closure_waitlist *list, struct closure *cl);
 void closure_sync(struct closure *cl);
 
-bool closure_trylock(struct closure *cl, struct closure *parent);
-void __closure_lock(struct closure *cl, struct closure *parent,
-		    struct closure_waitlist *wait_list);
-
-void do_closure_timer_init(struct closure *cl);
-bool __closure_delay(struct closure *cl, unsigned long delay,
-		     struct timer_list *timer);
-void __closure_flush(struct closure *cl, struct timer_list *timer);
-void __closure_flush_sync(struct closure *cl, struct timer_list *timer);
-
 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 
 void closure_debug_init(void);
@@ -339,200 +205,97 @@
 #endif
 }
 
-static inline void closure_get(struct closure *cl)
+static inline void closure_set_waiting(struct closure *cl, unsigned long f)
 {
 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
-	BUG_ON((atomic_inc_return(&cl->remaining) &
-		CLOSURE_REMAINING_MASK) <= 1);
-#else
-	atomic_inc(&cl->remaining);
+	cl->waiting_on = f;
 #endif
 }
 
-static inline void closure_set_stopped(struct closure *cl)
+static inline void __closure_end_sleep(struct closure *cl)
 {
-	atomic_sub(CLOSURE_RUNNING, &cl->remaining);
+	__set_current_state(TASK_RUNNING);
+
+	if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
+		atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
 }
 
-static inline bool closure_is_stopped(struct closure *cl)
+static inline void __closure_start_sleep(struct closure *cl)
 {
-	return !(atomic_read(&cl->remaining) & CLOSURE_RUNNING);
+	closure_set_ip(cl);
+	cl->task = current;
+	set_current_state(TASK_UNINTERRUPTIBLE);
+
+	if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
+		atomic_add(CLOSURE_SLEEPING, &cl->remaining);
 }
 
-static inline bool closure_is_unlocked(struct closure *cl)
+static inline void closure_set_stopped(struct closure *cl)
 {
-	return atomic_read(&cl->remaining) == -1;
+	atomic_sub(CLOSURE_RUNNING, &cl->remaining);
 }
 
-static inline void do_closure_init(struct closure *cl, struct closure *parent,
-				   bool running)
+static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
+				  struct workqueue_struct *wq)
 {
-	switch (cl->type) {
-	case TYPE_closure_with_timer:
-	case TYPE_closure_with_waitlist_and_timer:
-		do_closure_timer_init(cl);
-	default:
-		break;
-	}
-
-	cl->parent = parent;
-	if (parent)
-		closure_get(parent);
-
-	if (running) {
-		closure_debug_create(cl);
-		atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
-	} else
-		atomic_set(&cl->remaining, -1);
-
+	BUG_ON(object_is_on_stack(cl));
 	closure_set_ip(cl);
+	cl->fn = fn;
+	cl->wq = wq;
+	/* between atomic_dec() in closure_put() */
+	smp_mb__before_atomic();
 }
 
-/*
- * Hack to get at the embedded closure if there is one, by doing an unsafe cast:
- * the result of __closure_type() is thrown away, it's used merely for type
- * checking.
- */
-#define __to_internal_closure(cl)				\
-({								\
-	BUILD_BUG_ON(__closure_type(*cl) > MAX_CLOSURE_TYPE);	\
-	(struct closure *) cl;					\
-})
-
-#define closure_init_type(cl, parent, running)			\
-do {								\
-	struct closure *_cl = __to_internal_closure(cl);	\
-	_cl->type = __closure_type(*(cl));			\
-	do_closure_init(_cl, parent, running);			\
-} while (0)
+static inline void closure_queue(struct closure *cl)
+{
+	struct workqueue_struct *wq = cl->wq;
+	if (wq) {
+		INIT_WORK(&cl->work, cl->work.func);
+		BUG_ON(!queue_work(wq, &cl->work));
+	} else
+		cl->fn(cl);
+}
 
 /**
- * __closure_init() - Initialize a closure, skipping the memset()
- *
- * May be used instead of closure_init() when memory has already been zeroed.
+ * closure_get - increment a closure's refcount
  */
-#define __closure_init(cl, parent)				\
-	closure_init_type(cl, parent, true)
+static inline void closure_get(struct closure *cl)
+{
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+	BUG_ON((atomic_inc_return(&cl->remaining) &
+		CLOSURE_REMAINING_MASK) <= 1);
+#else
+	atomic_inc(&cl->remaining);
+#endif
+}
 
 /**
- * closure_init() - Initialize a closure, setting the refcount to 1
+ * closure_init - Initialize a closure, setting the refcount to 1
  * @cl:		closure to initialize
  * @parent:	parent of the new closure. cl will take a refcount on it for its
  *		lifetime; may be NULL.
  */
-#define closure_init(cl, parent)				\
-do {								\
-	memset((cl), 0, sizeof(*(cl)));				\
-	__closure_init(cl, parent);				\
-} while (0)
-
-static inline void closure_init_stack(struct closure *cl)
+static inline void closure_init(struct closure *cl, struct closure *parent)
 {
 	memset(cl, 0, sizeof(struct closure));
-	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|
-		   CLOSURE_BLOCKING|CLOSURE_STACK);
-}
-
-/**
- * closure_init_unlocked() - Initialize a closure but leave it unlocked.
- * @cl:		closure to initialize
- *
- * For when the closure will be used as a lock. The closure may not be used
- * until after a closure_lock() or closure_trylock().
- */
-#define closure_init_unlocked(cl)				\
-do {								\
-	memset((cl), 0, sizeof(*(cl)));				\
-	closure_init_type(cl, NULL, false);			\
-} while (0)
-
-/**
- * closure_lock() - lock and initialize a closure.
- * @cl:		the closure to lock
- * @parent:	the new parent for this closure
- *
- * The closure must be of one of the types that has a waitlist (otherwise we
- * wouldn't be able to sleep on contention).
- *
- * @parent has exactly the same meaning as in closure_init(); if non null, the
- * closure will take a reference on @parent which will be released when it is
- * unlocked.
- */
-#define closure_lock(cl, parent)				\
-	__closure_lock(__to_internal_closure(cl), parent, &(cl)->wait)
-
-/**
- * closure_delay() - delay some number of jiffies
- * @cl:		the closure that will sleep
- * @delay:	the delay in jiffies
- *
- * Takes a refcount on @cl which will be released after @delay jiffies; this may
- * be used to have a function run after a delay with continue_at(), or
- * closure_sync() may be used for a convoluted version of msleep().
- */
-#define closure_delay(cl, delay)			\
-	__closure_delay(__to_internal_closure(cl), delay, &(cl)->timer)
-
-#define closure_flush(cl)				\
-	__closure_flush(__to_internal_closure(cl), &(cl)->timer)
-
-#define closure_flush_sync(cl)				\
-	__closure_flush_sync(__to_internal_closure(cl), &(cl)->timer)
-
-static inline void __closure_end_sleep(struct closure *cl)
-{
-	__set_current_state(TASK_RUNNING);
+	cl->parent = parent;
+	if (parent)
+		closure_get(parent);
 
-	if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
-		atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
-}
+	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
 
-static inline void __closure_start_sleep(struct closure *cl)
-{
+	closure_debug_create(cl);
 	closure_set_ip(cl);
-	cl->task = current;
-	set_current_state(TASK_UNINTERRUPTIBLE);
-
-	if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
-		atomic_add(CLOSURE_SLEEPING, &cl->remaining);
 }
 
-/**
- * closure_blocking() - returns true if the closure is in blocking mode.
- *
- * If a closure is in blocking mode, closure_wait_event() will sleep until the
- * condition is true instead of waiting asynchronously.
- */
-static inline bool closure_blocking(struct closure *cl)
-{
-	return atomic_read(&cl->remaining) & CLOSURE_BLOCKING;
-}
-
-/**
- * set_closure_blocking() - put a closure in blocking mode.
- *
- * If a closure is in blocking mode, closure_wait_event() will sleep until the
- * condition is true instead of waiting asynchronously.
- *
- * Not thread safe - can only be called by the thread running the closure.
- */
-static inline void set_closure_blocking(struct closure *cl)
-{
-	if (!closure_blocking(cl))
-		atomic_add(CLOSURE_BLOCKING, &cl->remaining);
-}
-
-/*
- * Not thread safe - can only be called by the thread running the closure.
- */
-static inline void clear_closure_blocking(struct closure *cl)
+static inline void closure_init_stack(struct closure *cl)
 {
-	if (closure_blocking(cl))
-		atomic_sub(CLOSURE_BLOCKING, &cl->remaining);
+	memset(cl, 0, sizeof(struct closure));
+	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|CLOSURE_STACK);
 }
 
 /**
- * closure_wake_up() - wake up all closures on a wait list.
+ * closure_wake_up - wake up all closures on a wait list.
  */
 static inline void closure_wake_up(struct closure_waitlist *list)
 {
@@ -540,119 +303,75 @@
 	__closure_wake_up(list);
 }
 
-/*
- * Wait on an event, synchronously or asynchronously - analogous to wait_event()
- * but for closures.
- *
- * The loop is oddly structured so as to avoid a race; we must check the
- * condition again after we've added ourself to the waitlist. We know if we were
- * already on the waitlist because closure_wait() returns false; thus, we only
- * schedule or break if closure_wait() returns false. If it returns true, we
- * just loop again - rechecking the condition.
- *
- * The __closure_wake_up() is necessary because we may race with the event
- * becoming true; i.e. we see event false -> wait -> recheck condition, but the
- * thread that made the event true may have called closure_wake_up() before we
- * added ourself to the wait list.
- *
- * We have to call closure_sync() at the end instead of just
- * __closure_end_sleep() because a different thread might've called
- * closure_wake_up() before us and gotten preempted before they dropped the
- * refcount on our closure. If this was a stack allocated closure, that would be
- * bad.
- */
-#define __closure_wait_event(list, cl, condition, _block)		\
-({									\
-	bool block = _block;						\
-	typeof(condition) ret;						\
-									\
-	while (1) {							\
-		ret = (condition);					\
-		if (ret) {						\
-			__closure_wake_up(list);			\
-			if (block)					\
-				closure_sync(cl);			\
-									\
-			break;						\
-		}							\
-									\
-		if (block)						\
-			__closure_start_sleep(cl);			\
-									\
-		if (!closure_wait(list, cl)) {				\
-			if (!block)					\
-				break;					\
-									\
-			schedule();					\
-		}							\
-	}								\
-									\
-	ret;								\
-})
-
 /**
- * closure_wait_event() - wait on a condition, synchronously or asynchronously.
- * @list:	the wait list to wait on
- * @cl:		the closure that is doing the waiting
- * @condition:	a C expression for the event to wait for
- *
- * If the closure is in blocking mode, sleeps until the @condition evaluates to
- * true - exactly like wait_event().
- *
- * If the closure is not in blocking mode, waits asynchronously; if the
- * condition is currently false the @cl is put onto @list and returns. @list
- * owns a refcount on @cl; closure_sync() or continue_at() may be used later to
- * wait for another thread to wake up @list, which drops the refcount on @cl.
+ * continue_at - jump to another function with barrier
+ *
+ * After @cl is no longer waiting on anything (i.e. all outstanding refs have
+ * been dropped with closure_put()), it will resume execution at @fn running out
+ * of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
  *
- * Returns the value of @condition; @cl will be on @list iff @condition was
- * false.
+ * NOTE: This macro expands to a return in the calling function!
  *
- * closure_wake_up(@list) must be called after changing any variable that could
- * cause @condition to become true.
+ * This is because after calling continue_at() you no longer have a ref on @cl,
+ * and whatever @cl owns may be freed out from under you - a running closure fn
+ * has a ref on its own closure which continue_at() drops.
  */
-#define closure_wait_event(list, cl, condition)				\
-	__closure_wait_event(list, cl, condition, closure_blocking(cl))
-
-#define closure_wait_event_async(list, cl, condition)			\
-	__closure_wait_event(list, cl, condition, false)
-
-#define closure_wait_event_sync(list, cl, condition)			\
-	__closure_wait_event(list, cl, condition, true)
-
-static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
-				  struct workqueue_struct *wq)
-{
-	BUG_ON(object_is_on_stack(cl));
-	closure_set_ip(cl);
-	cl->fn = fn;
-	cl->wq = wq;
-	/* between atomic_dec() in closure_put() */
-	smp_mb__before_atomic_dec();
-}
-
 #define continue_at(_cl, _fn, _wq)					\
 do {									\
 	set_closure_fn(_cl, _fn, _wq);					\
 	closure_sub(_cl, CLOSURE_RUNNING + 1);				\
-	return;								\
 } while (0)
 
+/**
+ * closure_return - finish execution of a closure
+ *
+ * This is used to indicate that @cl is finished: when all outstanding refs on
+ * @cl have been dropped @cl's ref on its parent closure (as passed to
+ * closure_init()) will be dropped, if one was specified - thus this can be
+ * thought of as returning to the parent closure.
+ */
 #define closure_return(_cl)	continue_at((_cl), NULL, NULL)
 
+/**
+ * continue_at_nobarrier - jump to another function without barrier
+ *
+ * Causes @fn to be executed out of @cl, in @wq context (or called directly if
+ * @wq is NULL).
+ *
+ * NOTE: like continue_at(), this macro expands to a return in the caller!
+ *
+ * The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
+ * thus it's not safe to touch anything protected by @cl after a
+ * continue_at_nobarrier().
+ */
 #define continue_at_nobarrier(_cl, _fn, _wq)				\
 do {									\
 	set_closure_fn(_cl, _fn, _wq);					\
-	closure_queue(cl);						\
-	return;								\
+	closure_queue(_cl);						\
 } while (0)
 
+/**
+ * closure_return - finish execution of a closure, with destructor
+ *
+ * Works like closure_return(), except @destructor will be called when all
+ * outstanding refs on @cl have been dropped; @destructor may be used to safely
+ * free the memory occupied by @cl, and it is called with the ref on the parent
+ * closure still held - so @destructor could safely return an item to a
+ * freelist protected by @cl's parent.
+ */
 #define closure_return_with_destructor(_cl, _destructor)		\
 do {									\
 	set_closure_fn(_cl, _destructor, NULL);				\
 	closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1);	\
-	return;								\
 } while (0)
 
+/**
+ * closure_call - execute @fn out of a new, uninitialized closure
+ *
+ * Typically used when running out of one closure, and we want to run @fn
+ * asynchronously out of a new closure - @parent will then wait for @cl to
+ * finish.
+ */
 static inline void closure_call(struct closure *cl, closure_fn fn,
 				struct workqueue_struct *wq,
 				struct closure *parent)
@@ -661,12 +380,4 @@
 	continue_at_nobarrier(cl, fn, wq);
 }
 
-static inline void closure_trylock_call(struct closure *cl, closure_fn fn,
-					struct workqueue_struct *wq,
-					struct closure *parent)
-{
-	if (closure_trylock(cl, parent))
-		continue_at_nobarrier(cl, fn, wq);
-}
-
 #endif /* _LINUX_CLOSURE_H */