Hi, I'm trying to understand the code that allocates a new buffer from a pipe's buffer ring. I'd like to write a patch that eliminates some duplicate code, to make it less error prone. In fs/pipe.c, pipe_write() locks pipe->rd_wait.lock while the pipe's head gets evaluated and incremented (all while pipe->mutex is locked). My limited understand is that holding this spinlock is important because it protects the head/tail accesses in pipe_readable() which is gets called by wait_event while the spinlock is held, but without pipe->mutex. However in fs/splice.c, splice_pipe_to_pipe() contains very similar code; a new buffer gets allocated, head gets incremented - but without caring for pipe->rd_wait.lock. Please help me understand the point of locking pipe->rd_wait.lock, and why it's necessary in pipe_write() but not in splice_pipe_to_pipe(). Is that a bug or am I missing something? Max
