btrfs: use assertion helpers for extent buffer read lock counters

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

@@ -4678,7 +4678,6 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	eb->bflags = 0;
 	rwlock_init(&eb->lock);
 	atomic_set(&eb->write_locks, 0);
-	atomic_set(&eb->read_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,
 #ifdef CONFIG_BTRFS_DEBUG
 	atomic_set(&eb->spinning_writers, 0);
 	atomic_set(&eb->spinning_readers, 0);
+	atomic_set(&eb->read_locks, 0);
 #endif
 
 	return eb;

fs/btrfs/extent_io.h

@@ -162,7 +162,6 @@ struct extent_buffer {
 
 	/* count of read lock holders on the extent buffer */
 	atomic_t write_locks;
-	atomic_t read_locks;
 	atomic_t blocking_writers;
 	atomic_t blocking_readers;
 	short lock_nested;
@@ -185,6 +184,7 @@ struct extent_buffer {
 #ifdef CONFIG_BTRFS_DEBUG
 	atomic_t spinning_writers;
 	atomic_t spinning_readers;
+	atomic_t read_locks;
 	struct list_head leak_list;
 #endif
 };

fs/btrfs/locking.c

@@ -164,7 +164,7 @@ void btrfs_tree_read_lock(struct extent_buffer *eb)
 			   atomic_read(&eb->blocking_writers) == 0);
 		goto again;
 	}
-	atomic_inc(&eb->read_locks);
+	btrfs_assert_tree_read_locks_get(eb);
 	btrfs_assert_spinning_readers_get(eb);
 }
 
@@ -183,7 +183,7 @@ int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
 		read_unlock(&eb->lock);
 		return 0;
 	}
-	atomic_inc(&eb->read_locks);
+	btrfs_assert_tree_read_locks_get(eb);
 	btrfs_assert_spinning_readers_get(eb);
 	return 1;
 }
@@ -204,7 +204,7 @@ int btrfs_try_tree_read_lock(struct extent_buffer *eb)
 		read_unlock(&eb->lock);
 		return 0;
 	}
-	atomic_inc(&eb->read_locks);
+	btrfs_assert_tree_read_locks_get(eb);
 	btrfs_assert_spinning_readers_get(eb);
 	return 1;
 }
@@ -248,7 +248,7 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb)
 	}
 	btrfs_assert_tree_read_locked(eb);
 	btrfs_assert_spinning_readers_put(eb);
-	atomic_dec(&eb->read_locks);
+	btrfs_assert_tree_read_locks_put(eb);
 	read_unlock(&eb->lock);
 }
 
@@ -272,7 +272,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
 	/* 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);
+	btrfs_assert_tree_read_locks_put(eb);
 }
 
 /*