Merge branch 'net-consolidate-page_is_pfmemalloc-usage'

Alexander Lobakin says:

====================
net: consolidate page_is_pfmemalloc() usage

page_is_pfmemalloc() is used mostly by networking drivers to test
if a page can be considered for reusing/recycling.
It doesn't write anything to the struct page itself, so its sole
argument can be constified, as well as the first argument of
skb_propagate_pfmemalloc().
In Page Pool core code, it can be simply inlined instead.
Most of the callers from NIC drivers were just doppelgangers of
the same condition tests. Derive them into a new common function
do deduplicate the code.

Resend of v3 [2]:
 - it missed Patchwork and Netdev archives, probably due to server-side
   issues.

Since v2 [1]:
 - use more intuitive name for the new inline function since there's
   nothing "reserved" in remote pages (Jakub Kicinski, John Hubbard);
 - fold likely() inside the helper itself to make driver code a bit
   fancier (Jakub Kicinski);
 - split function introduction and using into two separate commits;
 - collect some more tags (Jesse Brandeburg, David Rientjes).

Since v1 [0]:
 - new: reduce code duplication by introducing a new common function
   to test if a page can be reused/recycled (David Rientjes);
 - collect autographs for Page Pool bits (Jesper Dangaard Brouer,
   Ilias Apalodimas).

[0] https://lore.kernel.org/netdev/20210125164612.243838-1-alobakin@pm.me
[1] https://lore.kernel.org/netdev/20210127201031.98544-1-alobakin@pm.me
[2] https://lore.kernel.org/lkml/20210131120844.7529-1-alobakin@pm.me
====================

Link: https://lore.kernel.org/r/20210202133030.5760-1-alobakin@pm.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 19 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ecdf8a8cd6ae..078633d43af9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1584,7 +1584,7 @@ struct address_space *page_mapping_file(struct page *page);
  * ALLOC_NO_WATERMARKS and the low watermark was not
  * met implying that the system is under some pressure.
  */
-static inline bool page_is_pfmemalloc(struct page *page)
+static inline bool page_is_pfmemalloc(const struct page *page)
 {
 	/*
 	 * Page index cannot be this large so this must be
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 9313b5aaf45b..0e42c53b8ca9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2939,12 +2939,28 @@ static inline struct page *dev_alloc_page(void)
 }
 
 /**
+ * dev_page_is_reusable - check whether a page can be reused for network Rx
+ * @page: the page to test
+ *
+ * A page shouldn't be considered for reusing/recycling if it was allocated
+ * under memory pressure or at a distant memory node.
+ *
+ * Returns false if this page should be returned to page allocator, true
+ * otherwise.
+ */
+static inline bool dev_page_is_reusable(const struct page *page)
+{
+	return likely(page_to_nid(page) == numa_mem_id() &&
+		      !page_is_pfmemalloc(page));
+}
+
+/**
  *	skb_propagate_pfmemalloc - Propagate pfmemalloc if skb is allocated after RX page
  *	@page: The page that was allocated from skb_alloc_page
  *	@skb: The skb that may need pfmemalloc set
  */
-static inline void skb_propagate_pfmemalloc(struct page *page,
-					     struct sk_buff *skb)
+static inline void skb_propagate_pfmemalloc(const struct page *page,
+					    struct sk_buff *skb)
 {
 	if (page_is_pfmemalloc(page))
 		skb->pfmemalloc = true;