btrfs: use assertion helpers for extent buffer write lock counters

Use the helpers where open coded. On non-debug builds, the warnings will
not trigger and extent_buffer::write_locks 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

@@ -4677,7 +4677,6 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	eb->fs_info = fs_info;
 	eb->bflags = 0;
 	rwlock_init(&eb->lock);
-	atomic_set(&eb->write_locks, 0);
 	atomic_set(&eb->blocking_readers, 0);
 	atomic_set(&eb->blocking_writers, 0);
 	eb->lock_nested = 0;
@@ -4701,6 +4700,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	atomic_set(&eb->spinning_writers, 0);
 	atomic_set(&eb->spinning_readers, 0);
 	atomic_set(&eb->read_locks, 0);
+	atomic_set(&eb->write_locks, 0);
 #endif
 
 	return eb;

fs/btrfs/extent_io.h

@@ -160,8 +160,6 @@ struct extent_buffer {
 	struct rcu_head rcu_head;
 	pid_t lock_owner;
 
-	/* count of read lock holders on the extent buffer */
-	atomic_t write_locks;
 	atomic_t blocking_writers;
 	atomic_t blocking_readers;
 	short lock_nested;
@@ -185,6 +183,7 @@ struct extent_buffer {
 	atomic_t spinning_writers;
 	atomic_t spinning_readers;
 	atomic_t read_locks;
+	atomic_t write_locks;
 	struct list_head leak_list;
 #endif
 };

fs/btrfs/locking.c

@@ -243,7 +243,7 @@ int btrfs_try_tree_write_lock(struct extent_buffer *eb)
 		write_unlock(&eb->lock);
 		return 0;
 	}
-	atomic_inc(&eb->write_locks);
+	btrfs_assert_tree_write_locks_get(eb);
 	btrfs_assert_spinning_writers_get(eb);
 	eb->lock_owner = current->pid;
 	return 1;
@@ -310,7 +310,7 @@ void btrfs_tree_lock(struct extent_buffer *eb)
 		goto again;
 	}
 	btrfs_assert_spinning_writers_get(eb);
-	atomic_inc(&eb->write_locks);
+	btrfs_assert_tree_write_locks_get(eb);
 	eb->lock_owner = current->pid;
 }
 
@@ -325,7 +325,7 @@ void btrfs_tree_unlock(struct extent_buffer *eb)
 
 	btrfs_assert_tree_locked(eb);
 	eb->lock_owner = 0;
-	atomic_dec(&eb->write_locks);
+	btrfs_assert_tree_write_locks_put(eb);
 
 	if (blockers) {
 		btrfs_assert_no_spinning_writers(eb);