From 6718b6f855a0b4962d54bd625be2718cb820cec6 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 16 Oct 2019 16:47:32 +0100 Subject: pipe: Allow pipes to have kernel-reserved slots Split pipe->ring_size into two numbers: (1) pipe->ring_size - indicates the hard size of the pipe ring. (2) pipe->max_usage - indicates the maximum number of pipe ring slots that userspace orchestrated events can fill. This allows for a pipe that is both writable by the general kernel notification facility and by userspace, allowing plenty of ring space for notifications to be added whilst preventing userspace from being able to pin too much unswappable kernel space. Signed-off-by: David Howells --- lib/iov_iter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'lib') diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 957f8828378a..be2fc5793ddd 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -395,7 +395,7 @@ static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t by i_head++; buf = &pipe->bufs[i_head & p_mask]; } - if (pipe_full(i_head, p_tail, pipe->ring_size)) + if (pipe_full(i_head, p_tail, pipe->max_usage)) return 0; buf->ops = &page_cache_pipe_buf_ops; @@ -528,7 +528,7 @@ static size_t push_pipe(struct iov_iter *i, size_t size, pipe->bufs[iter_head & p_mask].len = PAGE_SIZE; iter_head++; } - while (!pipe_full(iter_head, p_tail, pipe->ring_size)) { + while (!pipe_full(iter_head, p_tail, pipe->max_usage)) { struct pipe_buffer *buf = &pipe->bufs[iter_head & p_mask]; struct page *page = alloc_page(GFP_USER); if (!page) -- cgit v1.2.3