net: introduce helper sendpages_ok()

Network drivers are using sendpage_ok() to check the first page of an
iterator in order to disable MSG_SPLICE_PAGES. The iterator can
represent list of contiguous pages.

When MSG_SPLICE_PAGES is enabled skb_splice_from_iter() is being used,
it requires all pages in the iterator to be sendable. Therefore it needs
to check that each page is sendable.

The patch introduces a helper sendpages_ok(), it returns true if all the
contiguous pages are sendable.

Drivers who want to send contiguous pages with MSG_SPLICE_PAGES may use
this helper to check whether the page list is OK. If the helper does not
return true, the driver should remove MSG_SPLICE_PAGES flag.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Ofir Gal <ofir.gal@volumez.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20240718084515.3833733-2-ofir.gal@volumez.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/net.h b/include/linux/net.h
index 688320b79fcc6d0e64b247ff1d0e1ca37dcaf056..b75bc534c1b351955ac2ada9da09c52bd3bdae3e 100644 (file)
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -322,6 +322,25 @@ static inline bool sendpage_ok(struct page *page)
        return !PageSlab(page) && page_count(page) >= 1;
 }
 
+/*
+ * Check sendpage_ok on contiguous pages.
+ */
+static inline bool sendpages_ok(struct page *page, size_t len, size_t offset)
+{
+       struct page *p = page + (offset >> PAGE_SHIFT);
+       size_t count = 0;
+
+       while (count < len) {
+               if (!sendpage_ok(p))
+                       return false;
+
+               p++;
+               count += PAGE_SIZE;
+       }
+
+       return true;
+}
+
 int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec,
                   size_t num, size_t len);
 int kernel_sendmsg_locked(struct sock *sk, struct msghdr *msg,