From 8d73f8f23e6b869b726cb01dd4747f56dc88660a Mon Sep 17 00:00:00 2001 From: Jonathan Lemon Date: Tue, 13 Aug 2019 10:45:09 -0700 Subject: [PATCH] page_pool: fix logic in __page_pool_get_cached __page_pool_get_cached() will return NULL when the ring is empty, even if there are pages present in the lookaside cache. It is also possible to refill the cache, and then return a NULL page. Restructure the logic so eliminate both cases. Signed-off-by: Jonathan Lemon Acked-by: Jesper Dangaard Brouer Acked-by: Ilias Apalodimas Signed-off-by: David S. Miller --- net/core/page_pool.c | 39 ++++++++++++++++----------------------- 1 file changed, 16 insertions(+), 23 deletions(-) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 31187ff55cbc..5bc65587f1c4 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -82,12 +82,9 @@ EXPORT_SYMBOL(page_pool_create); static struct page *__page_pool_get_cached(struct page_pool *pool) { struct ptr_ring *r = &pool->ring; + bool refill = false; struct page *page; - /* Quicker fallback, avoid locks when ring is empty */ - if (__ptr_ring_empty(r)) - return NULL; - /* Test for safe-context, caller should provide this guarantee */ if (likely(in_serving_softirq())) { if (likely(pool->alloc.count)) { @@ -95,27 +92,23 @@ static struct page *__page_pool_get_cached(struct page_pool *pool) page = pool->alloc.cache[--pool->alloc.count]; return page; } - /* Slower-path: Alloc array empty, time to refill - * - * Open-coded bulk ptr_ring consumer. - * - * Discussion: the ring consumer lock is not really - * needed due to the softirq/NAPI protection, but - * later need the ability to reclaim pages on the - * ring. Thus, keeping the locks. - */ - spin_lock(&r->consumer_lock); - while ((page = __ptr_ring_consume(r))) { - if (pool->alloc.count == PP_ALLOC_CACHE_REFILL) - break; - pool->alloc.cache[pool->alloc.count++] = page; - } - spin_unlock(&r->consumer_lock); - return page; + refill = true; } - /* Slow-path: Get page from locked ring queue */ - page = ptr_ring_consume(&pool->ring); + /* 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); return page; } -- 2.30.2