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[73.170.51.167]) by smtp.gmail.com with ESMTPSA id p12-20020a170902eacc00b001dc3c3be4adsm7205550pld.297.2024.03.26.12.25.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Mar 2024 12:25:08 -0700 (PDT) Date: Tue, 26 Mar 2024 12:25:06 -0700 From: Vishal Moola To: Qi Zheng Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, rppt@kernel.org, willy@infradead.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] mm: pgtable: add missing pt_index to struct ptdesc Message-ID: References: <283624c2af45fb2090b41a6b1b5481bb0a45bad7.1709541697.git.zhengqi.arch@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <283624c2af45fb2090b41a6b1b5481bb0a45bad7.1709541697.git.zhengqi.arch@bytedance.com> On Mon, Mar 04, 2024 at 07:07:19PM +0800, Qi Zheng wrote: > In s390, the page->index field is used for gmap (see gmap_shadow_pgt()), > so add the corresponding pt_index to struct ptdesc and add a comment to > clarify this. Yes s390 gmap 'uses' page->index, but not for the purpose page->index is supposed to hold. It's alright to have a variable here, but I'd rather see it named something more appropriate to the purporse it serves. You can take look at this patch from v5 of my ptdesc conversion series for more info: https://lore.kernel.org/linux-mm/20230622205745.79707-3-vishal.moola@gmail.com/ > Signed-off-by: Qi Zheng > --- > include/linux/mm_types.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 5ea77969daae..5240bd7bca33 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -425,6 +425,7 @@ FOLIO_MATCH(compound_head, _head_2a); > * @_pt_pad_1: Padding that aliases with page's compound head. > * @pmd_huge_pte: Protected by ptdesc->ptl, used for THPs. > * @__page_mapping: Aliases with page->mapping. Unused for page tables. > + * @pt_index: Used for s390 gmap. > * @pt_mm: Used for x86 pgds. > * @pt_frag_refcount: For fragmented page table tracking. Powerpc only. > * @_pt_pad_2: Padding to ensure proper alignment. > @@ -450,6 +451,7 @@ struct ptdesc { > unsigned long __page_mapping; > > union { > + pgoff_t pt_index; > struct mm_struct *pt_mm; > atomic_t pt_frag_refcount; > }; > @@ -475,6 +477,7 @@ TABLE_MATCH(flags, __page_flags); > TABLE_MATCH(compound_head, pt_list); > TABLE_MATCH(compound_head, _pt_pad_1); > TABLE_MATCH(mapping, __page_mapping); > +TABLE_MATCH(index, pt_index); > TABLE_MATCH(rcu_head, pt_rcu_head); > TABLE_MATCH(page_type, __page_type); > TABLE_MATCH(_refcount, __page_refcount); > -- > 2.30.2 >