diff --git a/fs/fat/file.c b/fs/fat/file.c
index 7018e1d..a4a3a3c 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -429,8 +429,10 @@
 	}
 
 	if (attr->ia_valid & ATTR_SIZE) {
+		down_write(&MSDOS_I(inode)->truncate_lock);
 		truncate_setsize(inode, attr->ia_size);
 		fat_truncate_blocks(inode, attr->ia_size);
+		up_write(&MSDOS_I(inode)->truncate_lock);
 	}
 
 	setattr_copy(inode, attr);