[PATCH 2/2] btrfs: replace waitqueue_actvie with cond_wake_up

[David Sterba <dsterba@suse.com>]

Use the wrappers and reduce the amount of low-level details about the
waitqueue management.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/compression.c   |  7 +------
 fs/btrfs/delayed-inode.c |  9 +++------
 fs/btrfs/dev-replace.c   | 10 ++++------
 fs/btrfs/extent-tree.c   |  7 +------
 fs/btrfs/inode.c         |  9 +++------
 fs/btrfs/locking.c       | 34 +++++++++++-----------------------
 fs/btrfs/ordered-data.c  | 14 ++++----------
 fs/btrfs/transaction.c   |  7 +------
 fs/btrfs/tree-log.c      | 28 ++++++++--------------------
 9 files changed, 36 insertions(+), 89 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 562c3e633403..2d2d7380d381 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1003,12 +1003,7 @@ static void __free_workspace(int type, struct list_head *workspace,
 		btrfs_compress_op[idx]->free_workspace(workspace);
 	atomic_dec(total_ws);
 wake:
-	/*
-	 * Make sure counter is updated before we wake up waiters.
-	 */
-	smp_mb();
-	if (waitqueue_active(ws_wait))
-		wake_up(ws_wait);
+	cond_wake_up(ws_wait);
 }
 
 static void free_workspace(int type, struct list_head *ws)
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index d06bef16ebd5..3e7f5f26ff0f 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -472,13 +472,10 @@ static void finish_one_item(struct btrfs_delayed_root *delayed_root)
 {
 	int seq = atomic_inc_return(&delayed_root->items_seq);
 
-	/*
-	 * atomic_dec_return implies a barrier for waitqueue_active
-	 */
+	/* atomic_dec_return implies a barrier for waitqueue_active */
 	if ((atomic_dec_return(&delayed_root->items) <
-	    BTRFS_DELAYED_BACKGROUND || seq % BTRFS_DELAYED_BATCH == 0) &&
-	    waitqueue_active(&delayed_root->wait))
-		wake_up(&delayed_root->wait);
+	    BTRFS_DELAYED_BACKGROUND || seq % BTRFS_DELAYED_BATCH == 0))
+		cond_wake_up_nomb(&delayed_root->wait);
 }
 
 static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index e279f04b3388..f498572155f1 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -928,9 +928,9 @@ void btrfs_dev_replace_clear_lock_blocking(
 	ASSERT(atomic_read(&dev_replace->read_locks) > 0);
 	ASSERT(atomic_read(&dev_replace->blocking_readers) > 0);
 	read_lock(&dev_replace->lock);
-	if (atomic_dec_and_test(&dev_replace->blocking_readers) &&
-	    waitqueue_active(&dev_replace->read_lock_wq))
-		wake_up(&dev_replace->read_lock_wq);
+	/* Barrier implied by atomic_dec_and_test */
+	if (atomic_dec_and_test(&dev_replace->blocking_readers))
+		cond_wake_up_nomb(&dev_replace->read_lock_wq);
 }
 
 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
@@ -941,9 +941,7 @@ void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
 {
 	percpu_counter_sub(&fs_info->bio_counter, amount);
-
-	if (waitqueue_active(&fs_info->replace_wait))
-		wake_up(&fs_info->replace_wait);
+	cond_wake_up_nomb(&fs_info->replace_wait);
 }
 
 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 2760292e1175..d57801711884 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10999,12 +10999,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
 void btrfs_end_write_no_snapshotting(struct btrfs_root *root)
 {
 	percpu_counter_dec(&root->subv_writers->counter);
-	/*
-	 * Make sure counter is updated before we wake up waiters.
-	 */
-	smp_mb();
-	if (waitqueue_active(&root->subv_writers->wait))
-		wake_up(&root->subv_writers->wait);
+	cond_wake_up(&root->subv_writers->wait);
 }
 
 int btrfs_start_write_no_snapshotting(struct btrfs_root *root)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fc5b7d82b842..b963b5b4734e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1168,13 +1168,10 @@ static noinline void async_cow_submit(struct btrfs_work *work)
 	nr_pages = (async_cow->end - async_cow->start + PAGE_SIZE) >>
 		PAGE_SHIFT;
 
-	/*
-	 * atomic_sub_return implies a barrier for waitqueue_active
-	 */
+	/* atomic_sub_return implies a barrier */
 	if (atomic_sub_return(nr_pages, &fs_info->async_delalloc_pages) <
-	    5 * SZ_1M &&
-	    waitqueue_active(&fs_info->async_submit_wait))
-		wake_up(&fs_info->async_submit_wait);
+	    5 * SZ_1M)
+		cond_wake_up_nomb(&fs_info->async_submit_wait);
 
 	if (async_cow->inode)
 		submit_compressed_extents(async_cow->inode, async_cow);
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 621083f8932c..cce666cd104e 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -78,22 +78,16 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
 		write_lock(&eb->lock);
 		WARN_ON(atomic_read(&eb->spinning_writers));
 		atomic_inc(&eb->spinning_writers);
-		/*
-		 * atomic_dec_and_test implies a barrier for waitqueue_active
-		 */
-		if (atomic_dec_and_test(&eb->blocking_writers) &&
-		    waitqueue_active(&eb->write_lock_wq))
-			wake_up(&eb->write_lock_wq);
+		/* atomic_dec_and_test implies a barrier */
+		if (atomic_dec_and_test(&eb->blocking_writers))
+			cond_wake_up_nomb(&eb->write_lock_wq);
 	} else if (rw == BTRFS_READ_LOCK_BLOCKING) {
 		BUG_ON(atomic_read(&eb->blocking_readers) == 0);
 		read_lock(&eb->lock);
 		atomic_inc(&eb->spinning_readers);
-		/*
-		 * atomic_dec_and_test implies a barrier for waitqueue_active
-		 */
-		if (atomic_dec_and_test(&eb->blocking_readers) &&
-		    waitqueue_active(&eb->read_lock_wq))
-			wake_up(&eb->read_lock_wq);
+		/* atomic_dec_and_test implies a barrier */
+		if (atomic_dec_and_test(&eb->blocking_readers))
+			cond_wake_up_nomb(&eb->read_lock_wq);
 	}
 }
 
@@ -233,12 +227,9 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
 	}
 	btrfs_assert_tree_read_locked(eb);
 	WARN_ON(atomic_read(&eb->blocking_readers) == 0);
-	/*
-	 * atomic_dec_and_test implies a barrier for waitqueue_active
-	 */
-	if (atomic_dec_and_test(&eb->blocking_readers) &&
-	    waitqueue_active(&eb->read_lock_wq))
-		wake_up(&eb->read_lock_wq);
+	/* atomic_dec_and_test implies a barrier */
+	if (atomic_dec_and_test(&eb->blocking_readers))
+		cond_wake_up_nomb(&eb->read_lock_wq);
 	atomic_dec(&eb->read_locks);
 }
 
@@ -287,12 +278,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb)
 	if (blockers) {
 		WARN_ON(atomic_read(&eb->spinning_writers));
 		atomic_dec(&eb->blocking_writers);
-		/*
-		 * Make sure counter is updated before we wake up waiters.
-		 */
+		/* Use the lighter barrier after atomic */
 		smp_mb__after_atomic();
-		if (waitqueue_active(&eb->write_lock_wq))
-			wake_up(&eb->write_lock_wq);
+		cond_wake_up_nomb(&eb->write_lock_wq);
 	} else {
 		WARN_ON(atomic_read(&eb->spinning_writers) != 1);
 		atomic_dec(&eb->spinning_writers);
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 9be98e42cfb6..66ff1419e2e0 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -356,11 +356,8 @@ int btrfs_dec_test_first_ordered_pending(struct inode *inode,
 
 	if (entry->bytes_left == 0) {
 		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
-		/*
-		 * Implicit memory barrier after test_and_set_bit
-		 */
-		if (waitqueue_active(&entry->wait))
-			wake_up(&entry->wait);
+		/* test_and_set_bit implies a barrier */
+		cond_wake_up_nomb(&entry->wait);
 	} else {
 		ret = 1;
 	}
@@ -423,11 +420,8 @@ int btrfs_dec_test_ordered_pending(struct inode *inode,
 
 	if (entry->bytes_left == 0) {
 		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
-		/*
-		 * Implicit memory barrier after test_and_set_bit
-		 */
-		if (waitqueue_active(&entry->wait))
-			wake_up(&entry->wait);
+		/* test_and_set_bit implies a barrier */
+		cond_wake_up_nomb(&entry->wait);
 	} else {
 		ret = 1;
 	}
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index eab15777ba88..f431223196a0 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -909,12 +909,7 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 	atomic_dec(&cur_trans->num_writers);
 	extwriter_counter_dec(cur_trans, trans->type);
 
-	/*
-	 * Make sure counter is updated before we wake up waiters.
-	 */
-	smp_mb();
-	if (waitqueue_active(&cur_trans->writer_wait))
-		wake_up(&cur_trans->writer_wait);
+	cond_wake_up(&cur_trans->writer_wait);
 	btrfs_put_transaction(cur_trans);
 
 	if (current->journal_info == trans)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 7b8fee45b29e..979fc02214d4 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -235,11 +235,8 @@ int btrfs_pin_log_trans(struct btrfs_root *root)
 void btrfs_end_log_trans(struct btrfs_root *root)
 {
 	if (atomic_dec_and_test(&root->log_writers)) {
-		/*
-		 * Implicit memory barrier after atomic_dec_and_test
-		 */
-		if (waitqueue_active(&root->log_writer_wait))
-			wake_up(&root->log_writer_wait);
+		/* atomic_dec_and_test implies a barrier */
+		cond_wake_up_nomb(&root->log_writer_wait);
 	}
 }
 
@@ -2965,11 +2962,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 
 	mutex_lock(&log_root_tree->log_mutex);
 	if (atomic_dec_and_test(&log_root_tree->log_writers)) {
-		/*
-		 * Implicit memory barrier after atomic_dec_and_test
-		 */
-		if (waitqueue_active(&log_root_tree->log_writer_wait))
-			wake_up(&log_root_tree->log_writer_wait);
+		/* atomic_dec_and_test implies a barrier */
+		cond_wake_up_nomb(&log_root_tree->log_writer_wait);
 	}
 
 	if (ret) {
@@ -3092,11 +3086,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	atomic_set(&log_root_tree->log_commit[index2], 0);
 	mutex_unlock(&log_root_tree->log_mutex);
 
-	/*
-	 * The barrier before waitqueue_active is implied by mutex_unlock
-	 */
-	if (waitqueue_active(&log_root_tree->log_commit_wait[index2]))
-		wake_up(&log_root_tree->log_commit_wait[index2]);
+	/* The barrier is implied by mutex_unlock */
+	cond_wake_up_nomb(&log_root_tree->log_commit_wait[index2]);
 out:
 	mutex_lock(&root->log_mutex);
 	btrfs_remove_all_log_ctxs(root, index1, ret);
@@ -3104,11 +3095,8 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
 	atomic_set(&root->log_commit[index1], 0);
 	mutex_unlock(&root->log_mutex);
 
-	/*
-	 * The barrier before waitqueue_active is implied by mutex_unlock
-	 */
-	if (waitqueue_active(&root->log_commit_wait[index1]))
-		wake_up(&root->log_commit_wait[index1]);
+	/* The barrier is implied by mutex_unlock */
+	cond_wake_up_nomb(&root->log_commit_wait[index1]);
 	return ret;
 }
 
-- 
2.16.2