mm/net: Rename and move page fragment handling from net/ to mm/

This change moves the __alloc_page_frag functionality out of the networking
stack and into the page allocation portion of mm.  The idea it so help make
this maintainable by placing it with other page allocation functions.

Since we are moving it from skbuff.c to page_alloc.c I have also renamed
the basic defines and structure from netdev_alloc_cache to page_frag_cache
to reflect that this is now part of a different kernel subsystem.

I have also added a simple __free_page_frag function which can handle
freeing the frags based on the skb->head pointer.  The model for this is
based off of __free_pages since we don't actually need to deal with all of
the cases that put_page handles.  I incorporated the virt_to_head_page call
and compound_order into the function as it actually allows for a signficant
size reduction by reducing code duplication.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 94 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index a3062ec341c3..dcc0e07abf47 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -347,100 +347,12 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
 }
 EXPORT_SYMBOL(build_skb);
 
-struct netdev_alloc_cache {
-	void * va;
-#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
-	__u16 offset;
-	__u16 size;
-#else
-	__u32 offset;
-#endif
-	/* we maintain a pagecount bias, so that we dont dirty cache line
-	 * containing page->_count every time we allocate a fragment.
-	 */
-	unsigned int		pagecnt_bias;
-	bool pfmemalloc;
-};
-static DEFINE_PER_CPU(struct netdev_alloc_cache, netdev_alloc_cache);
-static DEFINE_PER_CPU(struct netdev_alloc_cache, napi_alloc_cache);
-
-static struct page *__page_frag_refill(struct netdev_alloc_cache *nc,
-				       gfp_t gfp_mask)
-{
-	struct page *page = NULL;
-	gfp_t gfp = gfp_mask;
-
-#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
-	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
-		    __GFP_NOMEMALLOC;
-	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
-				NETDEV_FRAG_PAGE_MAX_ORDER);
-	nc->size = page ? NETDEV_FRAG_PAGE_MAX_SIZE : PAGE_SIZE;
-#endif
-	if (unlikely(!page))
-		page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
-
-	nc->va = page ? page_address(page) : NULL;
-
-	return page;
-}
-
-static void *__alloc_page_frag(struct netdev_alloc_cache *nc,
-			       unsigned int fragsz, gfp_t gfp_mask)
-{
-	unsigned int size = PAGE_SIZE;
-	struct page *page;
-	int offset;
-
-	if (unlikely(!nc->va)) {
-refill:
-		page = __page_frag_refill(nc, gfp_mask);
-		if (!page)
-			return NULL;
-
-#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
-		/* if size can vary use size else just use PAGE_SIZE */
-		size = nc->size;
-#endif
-		/* Even if we own the page, we do not use atomic_set().
-		 * This would break get_page_unless_zero() users.
-		 */
-		atomic_add(size - 1, &page->_count);
-
-		/* reset page count bias and offset to start of new frag */
-		nc->pfmemalloc = page->pfmemalloc;
-		nc->pagecnt_bias = size;
-		nc->offset = size;
-	}
-
-	offset = nc->offset - fragsz;
-	if (unlikely(offset < 0)) {
-		page = virt_to_page(nc->va);
-
-		if (!atomic_sub_and_test(nc->pagecnt_bias, &page->_count))
-			goto refill;
-
-#if (PAGE_SIZE < NETDEV_FRAG_PAGE_MAX_SIZE)
-		/* if size can vary use size else just use PAGE_SIZE */
-		size = nc->size;
-#endif
-		/* OK, page count is 0, we can safely set it */
-		atomic_set(&page->_count, size);
-
-		/* reset page count bias and offset to start of new frag */
-		nc->pagecnt_bias = size;
-		offset = size - fragsz;
-	}
-
-	nc->pagecnt_bias--;
-	nc->offset = offset;
-
-	return nc->va + offset;
-}
+static DEFINE_PER_CPU(struct page_frag_cache, netdev_alloc_cache);
+static DEFINE_PER_CPU(struct page_frag_cache, napi_alloc_cache);
 
 static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
 {
-	struct netdev_alloc_cache *nc;
+	struct page_frag_cache *nc;
 	unsigned long flags;
 	void *data;
 
@@ -466,7 +378,7 @@ EXPORT_SYMBOL(netdev_alloc_frag);
 
 static void *__napi_alloc_frag(unsigned int fragsz, gfp_t gfp_mask)
 {
-	struct netdev_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
+	struct page_frag_cache *nc = this_cpu_ptr(&napi_alloc_cache);
 
 	return __alloc_page_frag(nc, fragsz, gfp_mask);
 }
@@ -493,7 +405,7 @@ EXPORT_SYMBOL(napi_alloc_frag);
 struct sk_buff *__netdev_alloc_skb(struct net_device *dev, unsigned int len,
 				   gfp_t gfp_mask)
 {
-	struct netdev_alloc_cache *nc;
+	struct page_frag_cache *nc;
 	unsigned long flags;
 	struct sk_buff *skb;
 	bool pfmemalloc;
@@ -556,7 +468,7 @@ EXPORT_SYMBOL(__netdev_alloc_skb);
 struct sk_buff *__napi_alloc_skb(struct napi_struct *napi, unsigned int len,
 				 gfp_t gfp_mask)
 {
-	struct netdev_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
+	struct page_frag_cache *nc = this_cpu_ptr(&napi_alloc_cache);
 	struct sk_buff *skb;
 	void *data;