From e7d553d69cf63aec7de0f38fed49ccbb30922e1e Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 14 Jan 2020 17:07:12 +0000 Subject: pipe: Add notification lossage handling Add handling for loss of notifications by having read() insert a loss-notification message after it has read the pipe buffer that was last in the ring when the loss occurred. Lossage can come about either by running out of notification descriptors or by running out of space in the pipe ring. Signed-off-by: David Howells --- fs/pipe.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'fs/pipe.c') diff --git a/fs/pipe.c b/fs/pipe.c index 0f9fd897ceb5..620a113f92eb 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -314,6 +314,30 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) unsigned int tail = pipe->tail; unsigned int mask = pipe->ring_size - 1; +#ifdef CONFIG_WATCH_QUEUE + if (pipe->note_loss) { + struct watch_notification n; + + if (total_len < 8) { + if (ret == 0) + ret = -ENOBUFS; + break; + } + + n.type = WATCH_TYPE_META; + n.subtype = WATCH_META_LOSS_NOTIFICATION; + n.info = watch_sizeof(n); + if (copy_to_iter(&n, sizeof(n), to) != sizeof(n)) { + if (ret == 0) + ret = -EFAULT; + break; + } + ret += sizeof(n); + total_len -= sizeof(n); + pipe->note_loss = false; + } +#endif + if (!pipe_empty(head, tail)) { struct pipe_buffer *buf = &pipe->bufs[tail & mask]; size_t chars = buf->len; @@ -355,6 +379,10 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) if (!buf->len) { pipe_buf_release(pipe, buf); spin_lock_irq(&pipe->rd_wait.lock); +#ifdef CONFIG_WATCH_QUEUE + if (buf->flags & PIPE_BUF_FLAG_LOSS) + pipe->note_loss = true; +#endif tail++; pipe->tail = tail; spin_unlock_irq(&pipe->rd_wait.lock); -- cgit v1.2.3