On Thu, Jul 10, 2025 at 11:35:33AM -0700, Mina Almasry wrote: > On Thu, Jul 10, 2025 at 1:28 AM Byungchul Park <byungchul@xxxxxx> wrote: > > > > Hi all, > > > > The MM subsystem is trying to reduce struct page to a single pointer. > > See the following link for your information: > > > > https://kernelnewbies.org/MatthewWilcox/Memdescs/Path > > > > The first step towards that is splitting struct page by its individual > > users, as has already been done with folio and slab. This patchset does > > that for page pool. > > > > Matthew Wilcox tried and stopped the same work, you can see in: > > > > https://lore.kernel.org/linux-mm/20230111042214.907030-1-willy@xxxxxxxxxxxxx/ > > > > I focused on removing the page pool members in struct page this time, > > not moving the allocation code of page pool from net to mm. It can be > > done later if needed. > > > > The final patch removing the page pool fields will be posted once all > > the converting of page to netmem are done: > > > > 1. converting use of the pp fields in struct page in prueth_swdata. > > 2. converting use of the pp fields in struct page in freescale driver. > > > > For our discussion, I'm sharing what the final patch looks like, in this > > cover letter. > > > > Byungchul > > --8<-- > > commit 1847d9890f798456b21ccb27aac7545303048492 > > Author: Byungchul Park <byungchul@xxxxxx> > > Date: Wed May 28 20:44:55 2025 +0900 > > > > mm, netmem: remove the page pool members in struct page > > > > Now that all the users of the page pool members in struct page have been > > gone, the members can be removed from struct page. > > > > However, since struct netmem_desc still uses the space in struct page, > > the important offsets should be checked properly, until struct > > netmem_desc has its own instance from slab. > > > > Remove the page pool members in struct page and modify static checkers > > for the offsets. > > > > Signed-off-by: Byungchul Park <byungchul@xxxxxx> > > > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > > index 32ba5126e221..db2fe0d0ebbf 100644 > > --- a/include/linux/mm_types.h > > +++ b/include/linux/mm_types.h > > @@ -120,17 +120,6 @@ struct page { > > */ > > unsigned long private; > > }; > > - struct { /* page_pool used by netstack */ > > - /** > > - * @pp_magic: magic value to avoid recycling non > > - * page_pool allocated pages. > > - */ > > - unsigned long pp_magic; > > - struct page_pool *pp; > > - unsigned long _pp_mapping_pad; > > - unsigned long dma_addr; > > - atomic_long_t pp_ref_count; > > - }; > > struct { /* Tail pages of compound page */ > > unsigned long compound_head; /* Bit zero is set */ > > }; > > diff --git a/include/net/netmem.h b/include/net/netmem.h > > index 8f354ae7d5c3..3414f184d018 100644 > > --- a/include/net/netmem.h > > +++ b/include/net/netmem.h > > @@ -42,11 +42,8 @@ struct netmem_desc { > > static_assert(offsetof(struct page, pg) == \ > > offsetof(struct netmem_desc, desc)) > > NETMEM_DESC_ASSERT_OFFSET(flags, _flags); > > -NETMEM_DESC_ASSERT_OFFSET(pp_magic, pp_magic); > > -NETMEM_DESC_ASSERT_OFFSET(pp, pp); > > -NETMEM_DESC_ASSERT_OFFSET(_pp_mapping_pad, _pp_mapping_pad); > > -NETMEM_DESC_ASSERT_OFFSET(dma_addr, dma_addr); > > -NETMEM_DESC_ASSERT_OFFSET(pp_ref_count, pp_ref_count); > > +NETMEM_DESC_ASSERT_OFFSET(lru, pp_magic); > > +NETMEM_DESC_ASSERT_OFFSET(mapping, _pp_mapping_pad); > > #undef NETMEM_DESC_ASSERT_OFFSET > > > > /* > > > Can you remove the above patch/diff from the cover letter? I added the diff for those who might get lost due to the lack of the final patch. However, sure, I will remove it. Byungchul > -- > Thanks, > Mina
