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Commit 8d73f8f2 authored by Jonathan Lemon's avatar Jonathan Lemon Committed by David S. Miller
Browse files

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: default avatarJonathan Lemon <jonathan.lemon@gmail.com>
Acked-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Acked-by: default avatarIlias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4b58c9b1

net/core/page_pool.c

+16 −23
Original line number Diff line number Diff line
@@ -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)) {
@@ -95,30 +92,26 @@ 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.

		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);

		while ((page = __ptr_ring_consume(r))) {

			if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)

				break;

			pool->alloc.cache[pool->alloc.count++] = page;

		}

	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;

}



	/* Slow-path: Get page from locked ring queue */

	page = ptr_ring_consume(&pool->ring);

	return page;

}



/* slow path */

noinline

static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,