Merge branch 'page_pool-NUMA-node-handling-fixes'

Jesper Dangaard Brouer says:

====================
page_pool: NUMA node handling fixes

The recently added NUMA changes (merged for v5.5) to page_pool, it both
contains a bug in handling NUMA_NO_NODE condition, and added code to
the fast-path.

This patchset fixes the bug and moves code out of fast-path. The first
patch contains a fix that should be considered for 5.5. The second
patch reduce code size and overhead in case CONFIG_NUMA is disabled.

Currently the NUMA_NO_NODE setting bug only affects driver 'ti_cpsw'
(drivers/net/ethernet/ti/), but after this patchset, we plan to move
other drivers (netsec and mvneta) to use NUMA_NO_NODE setting.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/page_pool.c

@@ -96,10 +96,65 @@ struct page_pool *page_pool_create(const struct page_pool_params *params)
 }
 EXPORT_SYMBOL(page_pool_create);
 
+static void __page_pool_return_page(struct page_pool *pool, struct page *page);
+
+noinline
+static struct page *page_pool_refill_alloc_cache(struct page_pool *pool,
+						 bool refill)
+{
+	struct ptr_ring *r = &pool->ring;
+	struct page *page;
+	int pref_nid; /* preferred NUMA node */
+
+	/* Quicker fallback, avoid locks when ring is empty */
+	if (__ptr_ring_empty(r))
+		return NULL;
+
+	/* Softirq guarantee CPU and thus NUMA node is stable. This,
+	 * assumes CPU refilling driver RX-ring will also run RX-NAPI.
+	 */
+#ifdef CONFIG_NUMA
+	pref_nid = (pool->p.nid == NUMA_NO_NODE) ? numa_mem_id() : pool->p.nid;
+#else
+	/* Ignore pool->p.nid setting if !CONFIG_NUMA, helps compiler */
+	pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */
+#endif
+
+	/* Slower-path: Get pages from locked ring queue */
+	spin_lock(&r->consumer_lock);
+
+	/* Refill alloc array, but only if NUMA match */
+	do {
+		page = __ptr_ring_consume(r);
+		if (unlikely(!page))
+			break;
+
+		if (likely(page_to_nid(page) == pref_nid)) {
+			pool->alloc.cache[pool->alloc.count++] = page;
+		} else {
+			/* NUMA mismatch;
+			 * (1) release 1 page to page-allocator and
+			 * (2) break out to fallthrough to alloc_pages_node.
+			 * This limit stress on page buddy alloactor.
+			 */
+			__page_pool_return_page(pool, page);
+			page = NULL;
+			break;
+		}
+	} while (pool->alloc.count < PP_ALLOC_CACHE_REFILL &&
+		 refill);
+
+	/* Return last page */
+	if (likely(pool->alloc.count > 0))
+		page = pool->alloc.cache[--pool->alloc.count];
+
+	spin_unlock(&r->consumer_lock);
+	return page;
+}
+
 /* fast path */
 static struct page *__page_pool_get_cached(struct page_pool *pool)
 {
-	struct ptr_ring *r = &pool->ring;
 	bool refill = false;
 	struct page *page;
 
@@ -113,20 +168,7 @@ static struct page *__page_pool_get_cached(struct page_pool *pool)
 		refill = true;
 	}
 
-	/* Quicker fallback, avoid locks when ring is empty */
-	if (__ptr_ring_empty(r))
-		return NULL;
-
-	/* Slow-path: Get page from locked ring queue,
-	 * refill alloc array if requested.
-	 */
-	spin_lock(&r->consumer_lock);
-	page = __ptr_ring_consume(r);
-	if (refill)
-		pool->alloc.count = __ptr_ring_consume_batched(r,
-							pool->alloc.cache,
-							PP_ALLOC_CACHE_REFILL);
-	spin_unlock(&r->consumer_lock);
+	page = page_pool_refill_alloc_cache(pool, refill);
 	return page;
 }
 
@@ -163,7 +205,11 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 	 */
 
 	/* Cache was empty, do real allocation */
+#ifdef CONFIG_NUMA
 	page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
+#else
+	page = alloc_pages(gfp, pool->p.order);
+#endif
 	if (!page)
 		return NULL;
 
@@ -311,13 +357,10 @@ static bool __page_pool_recycle_direct(struct page *page,
 
 /* page is NOT reusable when:
  * 1) allocated when system is under some pressure. (page_is_pfmemalloc)
- * 2) belongs to a different NUMA node than pool->p.nid.
- *
- * To update pool->p.nid users must call page_pool_update_nid.
  */
 static bool pool_page_reusable(struct page_pool *pool, struct page *page)
 {
-	return !page_is_pfmemalloc(page) && page_to_nid(page) == pool->p.nid;
+	return !page_is_pfmemalloc(page);
 }
 
 void __page_pool_put_page(struct page_pool *pool, struct page *page,
@@ -484,7 +527,15 @@ EXPORT_SYMBOL(page_pool_destroy);
 /* Caller must provide appropriate safe context, e.g. NAPI. */
 void page_pool_update_nid(struct page_pool *pool, int new_nid)
 {
+	struct page *page;
+
 	trace_page_pool_update_nid(pool, new_nid);
 	pool->p.nid = new_nid;
+
+	/* Flush pool alloc cache, as refill will check NUMA node */
+	while (pool->alloc.count) {
+		page = pool->alloc.cache[--pool->alloc.count];
+		__page_pool_return_page(pool, page);
+	}
 }
 EXPORT_SYMBOL(page_pool_update_nid);