btrfs: use assertion helpers for spinning readers

Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::spining_readers become unused and can be
moved to the appropriate section, saving a few bytes.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4681,7 +4681,6 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	atomic_set(&eb->read_locks, 0);
 	atomic_set(&eb->blocking_readers, 0);
 	atomic_set(&eb->blocking_writers, 0);
-	atomic_set(&eb->spinning_readers, 0);
 	eb->lock_nested = 0;
 	init_waitqueue_head(&eb->write_lock_wq);
 	init_waitqueue_head(&eb->read_lock_wq);
@@ -4701,6 +4700,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 
 #ifdef CONFIG_BTRFS_DEBUG
 	atomic_set(&eb->spinning_writers, 0);
+	atomic_set(&eb->spinning_readers, 0);
 #endif
 
 	return eb;

fs/btrfs/extent_io.h

@@ -165,7 +165,6 @@ struct extent_buffer {
 	atomic_t read_locks;
 	atomic_t blocking_writers;
 	atomic_t blocking_readers;
-	atomic_t spinning_readers;
 	short lock_nested;
 	/* >= 0 if eb belongs to a log tree, -1 otherwise */
 	short log_index;
@@ -185,6 +184,7 @@ struct extent_buffer {
 	struct page *pages[INLINE_EXTENT_BUFFER_PAGES];
 #ifdef CONFIG_BTRFS_DEBUG
 	atomic_t spinning_writers;
+	atomic_t spinning_readers;
 	struct list_head leak_list;
 #endif
 };

fs/btrfs/locking.c

@@ -62,8 +62,7 @@ void btrfs_set_lock_blocking_read(struct extent_buffer *eb)
 		return;
 	btrfs_assert_tree_read_locked(eb);
 	atomic_inc(&eb->blocking_readers);
-	WARN_ON(atomic_read(&eb->spinning_readers) == 0);
-	atomic_dec(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_put(eb);
 	read_unlock(&eb->lock);
 }
 
@@ -95,7 +94,7 @@ void btrfs_clear_lock_blocking_read(struct extent_buffer *eb)
 		return;
 	BUG_ON(atomic_read(&eb->blocking_readers) == 0);
 	read_lock(&eb->lock);
-	atomic_inc(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_get(eb);
 	/* atomic_dec_and_test implies a barrier */
 	if (atomic_dec_and_test(&eb->blocking_readers))
 		cond_wake_up_nomb(&eb->read_lock_wq);
@@ -150,7 +149,7 @@ void btrfs_tree_read_lock(struct extent_buffer *eb)
 		goto again;
 	}
 	atomic_inc(&eb->read_locks);
-	atomic_inc(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_get(eb);
 }
 
 /*
@@ -169,7 +168,7 @@ int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
 		return 0;
 	}
 	atomic_inc(&eb->read_locks);
-	atomic_inc(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_get(eb);
 	return 1;
 }
 
@@ -190,7 +189,7 @@ int btrfs_try_tree_read_lock(struct extent_buffer *eb)
 		return 0;
 	}
 	atomic_inc(&eb->read_locks);
-	atomic_inc(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_get(eb);
 	return 1;
 }
 
@@ -232,8 +231,7 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb)
 		return;
 	}
 	btrfs_assert_tree_read_locked(eb);
-	WARN_ON(atomic_read(&eb->spinning_readers) == 0);
-	atomic_dec(&eb->spinning_readers);
+	btrfs_assert_spinning_readers_put(eb);
 	atomic_dec(&eb->read_locks);
 	read_unlock(&eb->lock);
 }