[RFC PATCH 16/21] lib: have __zerocopy_sg_from_iter get netgpu pages for a sk

[Jonathan Lemon <jonathan.lemon@gmail.com>]

If a sock is marked as sending zc data, have the iterator
retrieve the correct zc pages from the netgpu module.

Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
---
 include/linux/uio.h |  4 ++++
 lib/iov_iter.c      | 45 +++++++++++++++++++++++++++++++++++++++++++++
 net/core/datagram.c |  6 +++++-
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 9576fd8158d7..d4c15205a248 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -227,6 +227,10 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages,
 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages,
 			size_t maxsize, size_t *start);
 int iov_iter_npages(const struct iov_iter *i, int maxpages);
+struct sock;
+ssize_t iov_iter_sk_get_pages(struct iov_iter *i, struct sock *sk,
+                   size_t maxsize, struct page **pages, unsigned maxpages,
+                   size_t *pgoff);
 
 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
 
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index bf538c2bec77..a50fa3999de3 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -10,6 +10,9 @@
 #include <linux/scatterlist.h>
 #include <linux/instrumented.h>
 
+#include <net/netgpu.h>
+#include <net/sock.h>
+
 #define PIPE_PARANOIA /* for now */
 
 #define iterate_iovec(i, n, __v, __p, skip, STEP) {	\
@@ -1349,6 +1352,48 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages);
 
+ssize_t iov_iter_sk_get_pages(struct iov_iter *i, struct sock *sk,
+		   size_t maxsize, struct page **pages, unsigned maxpages,
+		   size_t *pgoff)
+{
+	const struct iovec *iov;
+	unsigned long addr;
+	struct iovec v;
+	size_t len;
+	unsigned n;
+	int ret;
+
+	if (!sk->sk_user_data)
+		return iov_iter_get_pages(i, pages, maxsize, maxpages, pgoff);
+
+	if (maxsize > i->count)
+		maxsize = i->count;
+
+	if (!iter_is_iovec(i))
+		return -EFAULT;
+
+	if (iov_iter_rw(i) != WRITE)
+		return -EFAULT;
+
+	iterate_iovec(i, maxsize, v, iov, i->iov_offset, ({
+		addr = (unsigned long)v.iov_base;
+		*pgoff = addr & (PAGE_SIZE - 1);
+		len = v.iov_len + *pgoff;
+
+		if (len > maxpages * PAGE_SIZE)
+			len = maxpages * PAGE_SIZE;
+
+		n = DIV_ROUND_UP(len, PAGE_SIZE);
+
+		ret = __netgpu_get_pages(sk, pages, addr, n);
+		if (ret > 0)
+			ret = (ret == n ? len : ret * PAGE_SIZE) - *pgoff;
+		return ret;
+	0;}));
+	return 0;
+}
+EXPORT_SYMBOL(iov_iter_sk_get_pages);
+
 static struct page **get_pages_array(size_t n)
 {
 	return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 639745d4f3b9..7dd8814c222a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -530,6 +530,10 @@ int skb_copy_datagram_iter(const struct sk_buff *skb, int offset,
 			   struct iov_iter *to, int len)
 {
 	trace_skb_copy_datagram_iovec(skb, len);
+	if (skb->zc_netgpu) {
+		pr_err("skb netgpu datagram on !netgpu sk\n");
+		return -EFAULT;
+	}
 	return __skb_datagram_iter(skb, offset, to, len, false,
 			simple_copy_to_iter, NULL);
 }
@@ -631,7 +635,7 @@ int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
 		if (frag == MAX_SKB_FRAGS)
 			return -EMSGSIZE;
 
-		copied = iov_iter_get_pages(from, pages, length,
+		copied = iov_iter_sk_get_pages(from, sk, length, pages,
 					    MAX_SKB_FRAGS - frag, &start);
 		if (copied < 0)
 			return -EFAULT;
-- 
2.24.1