@anchor{Synchronizing File Access}
You must make sure that system calls are properly synchronized so that
any number of user processes can make them at once. In particular, it
-is not safe to call into the filesystem code provided in the
+is not safe to call into the file system code provided in the
@file{filesys} directory from multiple threads at once. For now, we
-recommend adding a single lock that controls access to the filesystem
+recommend adding a single lock that controls access to the file system
code. You should acquire this lock before calling any functions in
the @file{filesys} directory, and release it afterward. Don't forget
that @func{process_execute} also accesses files. @strong{For now, we