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Message-ID: <5296508e-5008-b5bb-ac2e-a0a69b720954@huawei.com>
Date: Thu, 15 Jun 2023 17:01:10 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Liang Chen <liangchen.linux@...il.com>, <hawk@...nel.org>,
<ilias.apalodimas@...aro.org>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
<pabeni@...hat.com>
Subject: Re: [PATCH net-next] page pool: not return page to alloc cache during
pool destruction
On 2023/6/15 9:36, Liang Chen wrote:
> When destroying a page pool, the alloc cache and recycle ring are emptied.
> If there are inflight pages, the retry process will periodically check the
> recycle ring for recently returned pages, but not the alloc cache (alloc
> cache is only emptied once). As a result, any pages returned to the alloc
> cache after the page pool destruction will be stuck there and cause the
> retry process to continuously look for inflight pages and report warnings.
It seems there is still page_pool_put[_full]_page() called with
allow_direct being true after page_pool_destroy() is call, which
is not allowed.
Normally the driver will call napi_disable() before
page_pool_destroy() to ensure there is no such page_pool_destroy()
calling with allow_direct being true after page_pool_destroy() is
called.
>
> To safeguard against this situation, any pages returning to the alloc cache
> after pool destruction should be prevented.
>
> Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> ---
> net/core/page_pool.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index a3e12a61d456..76255313d349 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -595,7 +595,7 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
> page_pool_dma_sync_for_device(pool, page,
> dma_sync_size);
>
> - if (allow_direct && in_softirq() &&
> + if (allow_direct && in_softirq() && !pool->destroy_cnt &&
The checking seems racy when __page_pool_put_page() and
page_pool_destroy() are called concurently.
> page_pool_recycle_in_cache(page, pool))
> return NULL;
>
>
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