Commit dbfe7d74 authored May 16, 2020 by John Hubbard Committed by David S. Miller May 17, 2020

rds: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages_fast(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages_fast() + put_page() calls to
pin_user_pages_fast() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/



Cc: David S. Miller <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-rdma@vger.kernel.org
Cc: rds-devel@oss.oracle.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9740a7ae

net/rds/info.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -162,7 +162,6 @@ int rds_info_getsockopt(struct socket sock, int optname, char __user optval,
		struct rds_info_lengths lens;
		unsigned long nr_pages = 0;
		unsigned long start;
		unsigned long i;
		rds_info_func func;
		struct page **pages = NULL;
		int ret;
		@@ -193,7 +192,7 @@ int rds_info_getsockopt(struct socket sock, int optname, char __user optval,
		ret = -ENOMEM;
		goto out;
		}
		ret = get_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
		ret = pin_user_pages_fast(start, nr_pages, FOLL_WRITE, pages);
		if (ret != nr_pages) {
		if (ret > 0)
		nr_pages = ret;
		@@ -235,8 +234,7 @@ call_func:
		ret = -EFAULT;

		out:
		for (i = 0; pages && i < nr_pages; i++)
		put_page(pages[i]);
		unpin_user_pages(pages, nr_pages);
		kfree(pages);

		return ret;

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