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[94.65.225.75]) by smtp.gmail.com with ESMTPSA id m26sm8126680wmg.17.2021.04.10.09.16.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Apr 2021 09:16:50 -0700 (PDT) Date: Sat, 10 Apr 2021 19:16:45 +0300 From: Ilias Apalodimas To: Matthew Wilcox Cc: Matteo Croce , netdev@vger.kernel.org, linux-mm@kvack.org, Ayush Sawal , Vinay Kumar Yadav , Rohit Maheshwari , "David S. Miller" , Jakub Kicinski , Thomas Petazzoni , Marcin Wojtas , Russell King , Mirko Lindner , Stephen Hemminger , Tariq Toukan , Jesper Dangaard Brouer , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Boris Pismenny , Arnd Bergmann , Andrew Morton , "Peter Zijlstra (Intel)" , Vlastimil Babka , Yu Zhao , Will Deacon , Michel Lespinasse , Fenghua Yu , Roman Gushchin , Hugh Dickins , Peter Xu , Jason Gunthorpe , Guoqing Jiang , Jonathan Lemon , Alexander Lobakin , Cong Wang , wenxu , Kevin Hao , Aleksandr Nogikh , Jakub Sitnicki , Marco Elver , Willem de Bruijn , Miaohe Lin , Yunsheng Lin , Guillaume Nault , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, Eric Dumazet , David Ahern , Lorenzo Bianconi , Saeed Mahameed , Andrew Lunn , Paolo Abeni Subject: Re: [PATCH net-next v3 2/5] mm: add a signature in struct page Message-ID: References: <20210409223801.104657-1-mcroce@linux.microsoft.com> <20210409223801.104657-3-mcroce@linux.microsoft.com> <20210410154824.GZ2531743@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210410154824.GZ2531743@casper.infradead.org> Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org Hi Matthew On Sat, Apr 10, 2021 at 04:48:24PM +0100, Matthew Wilcox wrote: > On Sat, Apr 10, 2021 at 12:37:58AM +0200, Matteo Croce wrote: > > This is needed by the page_pool to avoid recycling a page not allocated > > via page_pool. > > Is the PageType mechanism more appropriate to your needs? It wouldn't > be if you use page->_mapcount (ie mapping it to userspace). Interesting! Please keep in mind this was written ~2018 and was stale on my branches for quite some time. So back then I did try to use PageType, but had not free bits. Looking at it again though, it's cleaned up. So yes I think this can be much much cleaner. Should we go and define a new PG_pagepool? Thanks! /Ilias > > > Signed-off-by: Matteo Croce > > --- > > include/linux/mm_types.h | 1 + > > include/net/page_pool.h | 2 ++ > > net/core/page_pool.c | 4 ++++ > > 3 files changed, 7 insertions(+) > > > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > > index 6613b26a8894..ef2d0d5f62e4 100644 > > --- a/include/linux/mm_types.h > > +++ b/include/linux/mm_types.h > > @@ -101,6 +101,7 @@ struct page { > > * 32-bit architectures. > > */ > > dma_addr_t dma_addr; > > + unsigned long signature; > > }; > > struct { /* slab, slob and slub */ > > union { > > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > > index b5b195305346..b30405e84b5e 100644 > > --- a/include/net/page_pool.h > > +++ b/include/net/page_pool.h > > @@ -63,6 +63,8 @@ > > */ > > #define PP_ALLOC_CACHE_SIZE 128 > > #define PP_ALLOC_CACHE_REFILL 64 > > +#define PP_SIGNATURE 0x20210303 > > + > > struct pp_alloc_cache { > > u32 count; > > void *cache[PP_ALLOC_CACHE_SIZE]; > > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > > index ad8b0707af04..2ae9b554ef98 100644 > > --- a/net/core/page_pool.c > > +++ b/net/core/page_pool.c > > @@ -232,6 +232,8 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool, > > page_pool_dma_sync_for_device(pool, page, pool->p.max_len); > > > > skip_dma_map: > > + page->signature = PP_SIGNATURE; > > + > > /* Track how many pages are held 'in-flight' */ > > pool->pages_state_hold_cnt++; > > > > @@ -302,6 +304,8 @@ void page_pool_release_page(struct page_pool *pool, struct page *page) > > DMA_ATTR_SKIP_CPU_SYNC); > > page->dma_addr = 0; > > skip_dma_unmap: > > + page->signature = 0; > > + > > /* This may be the last page returned, releasing the pool, so > > * it is not safe to reference pool afterwards. > > */ > > -- > > 2.30.2 > >