1 files changed, 133 insertions, 178 deletions

diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index ff0b0be92d61..6c6f3bb58f4e 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -1,20 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2007 Oracle.  All rights reserved.
  * Copyright (C) 2014 Fujitsu.  All rights reserved.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License v2 as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 021110-1307, USA.
  */
 
 #include <linux/kthread.h>
@@ -22,17 +9,18 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/freezer.h>
+#include <trace/events/btrfs.h>
 #include "async-thread.h"
-#include "ctree.h"
 
-#define WORK_DONE_BIT 0
-#define WORK_ORDER_DONE_BIT 1
-#define WORK_HIGH_PRIO_BIT 2
+enum {
+	WORK_DONE_BIT,
+	WORK_ORDER_DONE_BIT,
+};
 
 #define NO_THRESHOLD (-1)
-#define DFT_THRESHOLD (32)
+#define DEFAULT_THRESHOLD (32)
 
-struct __btrfs_workqueue {
+struct btrfs_workqueue {
 	struct workqueue_struct *normal_wq;
 
 	/* File system this workqueue services */
@@ -59,86 +47,56 @@ struct __btrfs_workqueue {
 	spinlock_t thres_lock;
 };
 
-struct btrfs_workqueue {
-	struct __btrfs_workqueue *normal;
-	struct __btrfs_workqueue *high;
-};
-
-static void normal_work_helper(struct btrfs_work *work);
-
-#define BTRFS_WORK_HELPER(name)					\
-void btrfs_##name(struct work_struct *arg)				\
-{									\
-	struct btrfs_work *work = container_of(arg, struct btrfs_work,	\
-					       normal_work);		\
-	normal_work_helper(work);					\
-}
-
-struct btrfs_fs_info *
-btrfs_workqueue_owner(struct __btrfs_workqueue *wq)
+struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct btrfs_workqueue *wq)
 {
 	return wq->fs_info;
 }
 
-struct btrfs_fs_info *
-btrfs_work_owner(struct btrfs_work *work)
+struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work)
 {
 	return work->wq->fs_info;
 }
 
-bool btrfs_workqueue_normal_congested(struct btrfs_workqueue *wq)
+bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq)
 {
 	/*
-	 * We could compare wq->normal->pending with num_online_cpus()
+	 * We could compare wq->pending with num_online_cpus()
 	 * to support "thresh == NO_THRESHOLD" case, but it requires
 	 * moving up atomic_inc/dec in thresh_queue/exec_hook. Let's
 	 * postpone it until someone needs the support of that case.
 	 */
-	if (wq->normal->thresh == NO_THRESHOLD)
+	if (wq->thresh == NO_THRESHOLD)
 		return false;
 
-	return atomic_read(&wq->normal->pending) > wq->normal->thresh * 2;
+	return atomic_read(&wq->pending) > wq->thresh * 2;
 }
 
-BTRFS_WORK_HELPER(worker_helper);
-BTRFS_WORK_HELPER(delalloc_helper);
-BTRFS_WORK_HELPER(flush_delalloc_helper);
-BTRFS_WORK_HELPER(cache_helper);
-BTRFS_WORK_HELPER(submit_helper);
-BTRFS_WORK_HELPER(fixup_helper);
-BTRFS_WORK_HELPER(endio_helper);
-BTRFS_WORK_HELPER(endio_meta_helper);
-BTRFS_WORK_HELPER(endio_meta_write_helper);
-BTRFS_WORK_HELPER(endio_raid56_helper);
-BTRFS_WORK_HELPER(endio_repair_helper);
-BTRFS_WORK_HELPER(rmw_helper);
-BTRFS_WORK_HELPER(endio_write_helper);
-BTRFS_WORK_HELPER(freespace_write_helper);
-BTRFS_WORK_HELPER(delayed_meta_helper);
-BTRFS_WORK_HELPER(readahead_helper);
-BTRFS_WORK_HELPER(qgroup_rescan_helper);
-BTRFS_WORK_HELPER(extent_refs_helper);
-BTRFS_WORK_HELPER(scrub_helper);
-BTRFS_WORK_HELPER(scrubwrc_helper);
-BTRFS_WORK_HELPER(scrubnc_helper);
-BTRFS_WORK_HELPER(scrubparity_helper);
-
-static struct __btrfs_workqueue *
-__btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info, const char *name,
-			unsigned int flags, int limit_active, int thresh)
+static void btrfs_init_workqueue(struct btrfs_workqueue *wq,
+				 struct btrfs_fs_info *fs_info)
 {
-	struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL);
+	wq->fs_info = fs_info;
+	atomic_set(&wq->pending, 0);
+	INIT_LIST_HEAD(&wq->ordered_list);
+	spin_lock_init(&wq->list_lock);
+	spin_lock_init(&wq->thres_lock);
+}
+
+struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
+					      const char *name, unsigned int flags,
+					      int limit_active, int thresh)
+{
+	struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL);
 
 	if (!ret)
 		return NULL;
 
-	ret->fs_info = fs_info;
+	btrfs_init_workqueue(ret, fs_info);
+
 	ret->limit_active = limit_active;
-	atomic_set(&ret->pending, 0);
 	if (thresh == 0)
-		thresh = DFT_THRESHOLD;
+		thresh = DEFAULT_THRESHOLD;
 	/* For low threshold, disabling threshold is a better choice */
-	if (thresh < DFT_THRESHOLD) {
+	if (thresh < DEFAULT_THRESHOLD) {
 		ret->current_active = limit_active;
 		ret->thresh = NO_THRESHOLD;
 	} else {
@@ -151,57 +109,41 @@ __btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info, const char *name,
 		ret->thresh = thresh;
 	}
 
-	if (flags & WQ_HIGHPRI)
-		ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
-						 ret->current_active, "btrfs",
-						 name);
-	else
-		ret->normal_wq = alloc_workqueue("%s-%s", flags,
-						 ret->current_active, "btrfs",
-						 name);
+	ret->normal_wq = alloc_workqueue("btrfs-%s", flags, ret->current_active,
+					 name);
 	if (!ret->normal_wq) {
 		kfree(ret);
 		return NULL;
 	}
 
-	INIT_LIST_HEAD(&ret->ordered_list);
-	spin_lock_init(&ret->list_lock);
-	spin_lock_init(&ret->thres_lock);
-	trace_btrfs_workqueue_alloc(ret, name, flags & WQ_HIGHPRI);
+	trace_btrfs_workqueue_alloc(ret, name);
 	return ret;
 }
 
-static inline void
-__btrfs_destroy_workqueue(struct __btrfs_workqueue *wq);
-
-struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
-					      const char *name,
-					      unsigned int flags,
-					      int limit_active,
-					      int thresh)
+struct btrfs_workqueue *btrfs_alloc_ordered_workqueue(
+				struct btrfs_fs_info *fs_info, const char *name,
+				unsigned int flags)
 {
-	struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL);
+	struct btrfs_workqueue *ret;
 
+	ret = kzalloc(sizeof(*ret), GFP_KERNEL);
 	if (!ret)
 		return NULL;
 
-	ret->normal = __btrfs_alloc_workqueue(fs_info, name,
-					      flags & ~WQ_HIGHPRI,
-					      limit_active, thresh);
-	if (!ret->normal) {
+	btrfs_init_workqueue(ret, fs_info);
+
+	/* Ordered workqueues don't allow @max_active adjustments. */
+	ret->limit_active = 1;
+	ret->current_active = 1;
+	ret->thresh = NO_THRESHOLD;
+
+	ret->normal_wq = alloc_ordered_workqueue("btrfs-%s", flags, name);
+	if (!ret->normal_wq) {
 		kfree(ret);
 		return NULL;
 	}
 
-	if (flags & WQ_HIGHPRI) {
-		ret->high = __btrfs_alloc_workqueue(fs_info, name, flags,
-						    limit_active, thresh);
-		if (!ret->high) {
-			__btrfs_destroy_workqueue(ret->normal);
-			kfree(ret);
-			return NULL;
-		}
-	}
+	trace_btrfs_workqueue_alloc(ret, name);
 	return ret;
 }
 
@@ -210,7 +152,7 @@ struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
  * This hook WILL be called in IRQ handler context,
  * so workqueue_set_max_active MUST NOT be called in this hook
  */
-static inline void thresh_queue_hook(struct __btrfs_workqueue *wq)
+static inline void thresh_queue_hook(struct btrfs_workqueue *wq)
 {
 	if (wq->thresh == NO_THRESHOLD)
 		return;
@@ -222,11 +164,11 @@ static inline void thresh_queue_hook(struct __btrfs_workqueue *wq)
  * This hook is called in kthread content.
  * So workqueue_set_max_active is called here.
  */
-static inline void thresh_exec_hook(struct __btrfs_workqueue *wq)
+static inline void thresh_exec_hook(struct btrfs_workqueue *wq)
 {
 	int new_current_active;
 	long pending;
-	int need_change = 0;
+	bool need_change = false;
 
 	if (wq->thresh == NO_THRESHOLD)
 		return;
@@ -254,34 +196,39 @@ static inline void thresh_exec_hook(struct __btrfs_workqueue *wq)
 		new_current_active--;
 	new_current_active = clamp_val(new_current_active, 1, wq->limit_active);
 	if (new_current_active != wq->current_active)  {
-		need_change = 1;
+		need_change = true;
 		wq->current_active = new_current_active;
 	}
 out:
 	spin_unlock(&wq->thres_lock);
 
-	if (need_change) {
+	if (need_change)
 		workqueue_set_max_active(wq->normal_wq, wq->current_active);
-	}
 }
 
-static void run_ordered_work(struct __btrfs_workqueue *wq)
+static void run_ordered_work(struct btrfs_workqueue *wq,
+			     struct btrfs_work *self)
 {
 	struct list_head *list = &wq->ordered_list;
 	struct btrfs_work *work;
 	spinlock_t *lock = &wq->list_lock;
 	unsigned long flags;
+	bool free_self = false;
 
 	while (1) {
-		void *wtag;
-
 		spin_lock_irqsave(lock, flags);
 		if (list_empty(list))
 			break;
-		work = list_entry(list->next, struct btrfs_work,
-				  ordered_list);
+		work = list_first_entry(list, struct btrfs_work, ordered_list);
 		if (!test_bit(WORK_DONE_BIT, &work->flags))
 			break;
+		/*
+		 * Orders all subsequent loads after reading WORK_DONE_BIT,
+		 * paired with the smp_mb__before_atomic in btrfs_work_helper
+		 * this guarantees that the ordered function will see all
+		 * updates from ordinary work function.
+		 */
+		smp_rmb();
 
 		/*
 		 * we are going to call the ordered done function, but
@@ -293,71 +240,103 @@ static void run_ordered_work(struct __btrfs_workqueue *wq)
 			break;
 		trace_btrfs_ordered_sched(work);
 		spin_unlock_irqrestore(lock, flags);
-		work->ordered_func(work);
+		work->ordered_func(work, false);
 
 		/* now take the lock again and drop our item from the list */
 		spin_lock_irqsave(lock, flags);
 		list_del(&work->ordered_list);
 		spin_unlock_irqrestore(lock, flags);
 
-		/*
-		 * We don't want to call the ordered free functions with the
-		 * lock held though. Save the work as tag for the trace event,
-		 * because the callback could free the structure.
-		 */
-		wtag = work;
-		work->ordered_free(work);
-		trace_btrfs_all_work_done(wq->fs_info, wtag);
+		if (work == self) {
+			/*
+			 * This is the work item that the worker is currently
+			 * executing.
+			 *
+			 * The kernel workqueue code guarantees non-reentrancy
+			 * of work items. I.e., if a work item with the same
+			 * address and work function is queued twice, the second
+			 * execution is blocked until the first one finishes. A
+			 * work item may be freed and recycled with the same
+			 * work function; the workqueue code assumes that the
+			 * original work item cannot depend on the recycled work
+			 * item in that case (see find_worker_executing_work()).
+			 *
+			 * Note that different types of Btrfs work can depend on
+			 * each other, and one type of work on one Btrfs
+			 * filesystem may even depend on the same type of work
+			 * on another Btrfs filesystem via, e.g., a loop device.
+			 * Therefore, we must not allow the current work item to
+			 * be recycled until we are really done, otherwise we
+			 * break the above assumption and can deadlock.
+			 */
+			free_self = true;
+		} else {
+			/*
+			 * We don't want to call the ordered free functions with
+			 * the lock held.
+			 */
+			work->ordered_func(work, true);
+			/* NB: work must not be dereferenced past this point. */
+			trace_btrfs_all_work_done(wq->fs_info, work);
+		}
 	}
 	spin_unlock_irqrestore(lock, flags);
+
+	if (free_self) {
+		self->ordered_func(self, true);
+		/* NB: self must not be dereferenced past this point. */
+		trace_btrfs_all_work_done(wq->fs_info, self);
+	}
 }
 
-static void normal_work_helper(struct btrfs_work *work)
+static void btrfs_work_helper(struct work_struct *normal_work)
 {
-	struct __btrfs_workqueue *wq;
-	void *wtag;
-	int need_order = 0;
+	struct btrfs_work *work = container_of(normal_work, struct btrfs_work,
+					       normal_work);
+	struct btrfs_workqueue *wq = work->wq;
+	bool need_order = false;
 
 	/*
 	 * We should not touch things inside work in the following cases:
-	 * 1) after work->func() if it has no ordered_free
+	 * 1) after work->func() if it has no ordered_func(..., true) to free
 	 *    Since the struct is freed in work->func().
 	 * 2) after setting WORK_DONE_BIT
 	 *    The work may be freed in other threads almost instantly.
 	 * So we save the needed things here.
 	 */
 	if (work->ordered_func)
-		need_order = 1;
-	wq = work->wq;
-	/* Safe for tracepoints in case work gets freed by the callback */
-	wtag = work;
+		need_order = true;
 
 	trace_btrfs_work_sched(work);
 	thresh_exec_hook(wq);
 	work->func(work);
 	if (need_order) {
+		/*
+		 * Ensures all memory accesses done in the work function are
+		 * ordered before setting the WORK_DONE_BIT. Ensuring the thread
+		 * which is going to executed the ordered work sees them.
+		 * Pairs with the smp_rmb in run_ordered_work.
+		 */
+		smp_mb__before_atomic();
 		set_bit(WORK_DONE_BIT, &work->flags);
-		run_ordered_work(wq);
+		run_ordered_work(wq, work);
+	} else {
+		/* NB: work must not be dereferenced past this point. */
+		trace_btrfs_all_work_done(wq->fs_info, work);
 	}
-	if (!need_order)
-		trace_btrfs_all_work_done(wq->fs_info, wtag);
 }
 
-void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t uniq_func,
-		     btrfs_func_t func,
-		     btrfs_func_t ordered_func,
-		     btrfs_func_t ordered_free)
+void btrfs_init_work(struct btrfs_work *work, btrfs_func_t func,
+		     btrfs_ordered_func_t ordered_func)
 {
 	work->func = func;
 	work->ordered_func = ordered_func;
-	work->ordered_free = ordered_free;
-	INIT_WORK(&work->normal_work, uniq_func);
+	INIT_WORK(&work->normal_work, btrfs_work_helper);
 	INIT_LIST_HEAD(&work->ordered_list);
 	work->flags = 0;
 }
 
-static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq,
-				      struct btrfs_work *work)
+void btrfs_queue_work(struct btrfs_workqueue *wq, struct btrfs_work *work)
 {
 	unsigned long flags;
 
@@ -372,46 +351,22 @@ static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq,
 	queue_work(wq->normal_wq, &work->normal_work);
 }
 
-void btrfs_queue_work(struct btrfs_workqueue *wq,
-		      struct btrfs_work *work)
-{
-	struct __btrfs_workqueue *dest_wq;
-
-	if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags) && wq->high)
-		dest_wq = wq->high;
-	else
-		dest_wq = wq->normal;
-	__btrfs_queue_work(dest_wq, work);
-}
-
-static inline void
-__btrfs_destroy_workqueue(struct __btrfs_workqueue *wq)
-{
-	destroy_workqueue(wq->normal_wq);
-	trace_btrfs_workqueue_destroy(wq);
-	kfree(wq);
-}
-
 void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
 {
 	if (!wq)
 		return;
-	if (wq->high)
-		__btrfs_destroy_workqueue(wq->high);
-	__btrfs_destroy_workqueue(wq->normal);
+	destroy_workqueue(wq->normal_wq);
+	trace_btrfs_workqueue_destroy(wq);
 	kfree(wq);
 }
 
 void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active)
 {
-	if (!wq)
-		return;
-	wq->normal->limit_active = limit_active;
-	if (wq->high)
-		wq->high->limit_active = limit_active;
+	if (wq)
+		wq->limit_active = limit_active;
 }
 
-void btrfs_set_work_high_priority(struct btrfs_work *work)
+void btrfs_flush_workqueue(struct btrfs_workqueue *wq)
 {
-	set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
+	flush_workqueue(wq->normal_wq);
 }