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Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Andrew Lunn , Eric Dumazet , Paolo Abeni , Ilias Apalodimas , Simon Horman , Andrew Morton , Mina Almasry , Yonglong Liu , Yunsheng Lin , Pavel Begunkov , Matthew Wilcox , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH net-next v7 1/2] page_pool: Move pp_magic check into helper functions In-Reply-To: References: <20250404-page-pool-track-dma-v7-0-ad34f069bc18@redhat.com> <20250404-page-pool-track-dma-v7-1-ad34f069bc18@redhat.com> <87cydoxsgs.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Mon, 07 Apr 2025 15:14:03 +0200 Message-ID: <87v7rgw1us.fsf@toke.dk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Zi Yan writes: > Resend to fix my signature. > > On 7 Apr 2025, at 4:53, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > >> "Zi Yan" writes: >> >>> On Fri Apr 4, 2025 at 6:18 AM EDT, Toke H=C3=B8iland-J=C3=B8rgensen wro= te: >>>> Since we are about to stash some more information into the pp_magic >>>> field, let's move the magic signature checks into a pair of helper >>>> functions so it can be changed in one place. >>>> >>>> Reviewed-by: Mina Almasry >>>> Tested-by: Yonglong Liu >>>> Acked-by: Jesper Dangaard Brouer >>>> Reviewed-by: Ilias Apalodimas >>>> Signed-off-by: Toke H=C3=B8iland-J=C3=B8rgensen >>>> --- >>>> drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 4 ++-- >>>> include/net/page_pool/types.h | 18 +++++++++++++++= +++ >>>> mm/page_alloc.c | 9 +++------ >>>> net/core/netmem_priv.h | 5 +++++ >>>> net/core/skbuff.c | 16 ++-------------- >>>> net/core/xdp.c | 4 ++-- >>>> 6 files changed, 32 insertions(+), 24 deletions(-) >>>> >>> >>> >>> >>>> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/typ= es.h >>>> index 36eb57d73abc6cfc601e700ca08be20fb8281055..df0d3c1608929605224feb= 26173135ff37951ef8 100644 >>>> --- a/include/net/page_pool/types.h >>>> +++ b/include/net/page_pool/types.h >>>> @@ -54,6 +54,14 @@ struct pp_alloc_cache { >>>> netmem_ref cache[PP_ALLOC_CACHE_SIZE]; >>>> }; >>>> >>>> +/* Mask used for checking in page_pool_page_is_pp() below. page->pp_m= agic is >>>> + * OR'ed with PP_SIGNATURE after the allocation in order to preserve = bit 0 for >>>> + * the head page of compound page and bit 1 for pfmemalloc page. >>>> + * page_is_pfmemalloc() is checked in __page_pool_put_page() to avoid= recycling >>>> + * the pfmemalloc page. >>>> + */ >>>> +#define PP_MAGIC_MASK ~0x3UL >>>> + >>>> /** >>>> * struct page_pool_params - page pool parameters >>>> * @fast: params accessed frequently on hotpath >>>> @@ -264,6 +272,11 @@ void page_pool_destroy(struct page_pool *pool); >>>> void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)= (void *), >>>> const struct xdp_mem_info *mem); >>>> void page_pool_put_netmem_bulk(netmem_ref *data, u32 count); >>>> + >>>> +static inline bool page_pool_page_is_pp(struct page *page) >>>> +{ >>>> + return (page->pp_magic & PP_MAGIC_MASK) =3D=3D PP_SIGNATURE; >>>> +} >>>> #else >>>> static inline void page_pool_destroy(struct page_pool *pool) >>>> { >>>> @@ -278,6 +291,11 @@ static inline void page_pool_use_xdp_mem(struct p= age_pool *pool, >>>> static inline void page_pool_put_netmem_bulk(netmem_ref *data, u32 co= unt) >>>> { >>>> } >>>> + >>>> +static inline bool page_pool_page_is_pp(struct page *page) >>>> +{ >>>> + return false; >>>> +} >>>> #endif >>>> >>>> void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref = netmem, >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index f51aa6051a99867d2d7d8c70aa7c30e523629951..347a3cc2c188f4a9ced85e= 0d198947be7c503526 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -55,6 +55,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> #include >>>> #include "internal.h" >>>> #include "shuffle.h" >>>> @@ -897,9 +898,7 @@ static inline bool page_expected_state(struct page= *page, >>>> #ifdef CONFIG_MEMCG >>>> page->memcg_data | >>>> #endif >>>> -#ifdef CONFIG_PAGE_POOL >>>> - ((page->pp_magic & ~0x3UL) =3D=3D PP_SIGNATURE) | >>>> -#endif >>>> + page_pool_page_is_pp(page) | >>>> (page->flags & check_flags))) >>>> return false; >>>> >>>> @@ -926,10 +925,8 @@ static const char *page_bad_reason(struct page *p= age, unsigned long flags) >>>> if (unlikely(page->memcg_data)) >>>> bad_reason =3D "page still charged to cgroup"; >>>> #endif >>>> -#ifdef CONFIG_PAGE_POOL >>>> - if (unlikely((page->pp_magic & ~0x3UL) =3D=3D PP_SIGNATURE)) >>>> + if (unlikely(page_pool_page_is_pp(page))) >>>> bad_reason =3D "page_pool leak"; >>>> -#endif >>>> return bad_reason; >>>> } >>>> >>> >>> I wonder if it is OK to make page allocation depend on page_pool from >>> net/page_pool. >> >> Why? It's not really a dependency, just a header include with a static >> inline function... > > The function is checking, not even modifying, an core mm data structure, > struct page, which is also used by almost all subsystems. I do not get > why the function is in net subsystem. Well, because it's using details of the PP definitions, so keeping it there nicely encapsulates things. I mean, that's the whole point of defining a wrapper function - encapsulating the logic :) >>> Would linux/mm.h be a better place for page_pool_page_is_pp()? >> >> That would require moving all the definitions introduced in patch 2, >> which I don't think is appropriate. > > Why? I do not see page_pool_page_is_pp() or PP_SIGNATURE is used anywhere > in patch 2. Look again. Patch 2 redefines PP_MAGIC_MASK in terms of all the other definitions. -Toke