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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id x11-20020a81630b000000b0056ffca5fb01sm370775ywb.117.2023.06.20.00.53.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jun 2023 00:53:07 -0700 (PDT) Date: Tue, 20 Jun 2023 00:53:03 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Gerald Schaefer , Vasily Gorbik , Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Russell King , "David S. Miller" , Michael Ellerman , "Aneesh Kumar K.V" , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Alexander Gordeev , Jann Horn , Vishal Moola , Vlastimil Babka , linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 08/12] mm/pgtable: add pte_free_defer() for pgtable as page In-Reply-To: <54cb04f-3762-987f-8294-91dafd8ebfb0@google.com> Message-ID: <3e5961a2-26e5-d1ab-5c4c-527e273e3cc5@google.com> References: <54cb04f-3762-987f-8294-91dafd8ebfb0@google.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add the generic pte_free_defer(), to call pte_free() via call_rcu(). pte_free_defer() will be called inside khugepaged's retract_page_tables() loop, where allocating extra memory cannot be relied upon. This version suits all those architectures which use an unfragmented page for one page table (none of whose pte_free()s use the mm arg which was passed to it). Signed-off-by: Hugh Dickins --- include/linux/mm_types.h | 4 ++++ include/linux/pgtable.h | 2 ++ mm/pgtable-generic.c | 20 ++++++++++++++++++++ 3 files changed, 26 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 1667a1bdb8a8..09335fa28c41 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -144,6 +144,10 @@ struct page { struct { /* Page table pages */ unsigned long _pt_pad_1; /* compound_head */ pgtable_t pmd_huge_pte; /* protected by page->ptl */ + /* + * A PTE page table page might be freed by use of + * rcu_head: which overlays those two fields above. + */ unsigned long _pt_pad_2; /* mapping */ union { struct mm_struct *pt_mm; /* x86 pgd, s390 */ diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 525f1782b466..d18d3e963967 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -112,6 +112,8 @@ static inline void pte_unmap(pte_t *pte) } #endif =20 +void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable); + /* Find an entry in the second-level page table.. */ #ifndef pmd_offset static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address) diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 5e85a625ab30..ab3741064bb8 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -13,6 +13,7 @@ #include #include #include +#include #include =20 /* @@ -230,6 +231,25 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, = unsigned long address, return pmd; } #endif + +/* arch define pte_free_defer in asm/pgalloc.h for its own implementation = */ +#ifndef pte_free_defer +static void pte_free_now(struct rcu_head *head) +{ + struct page *page; + + page =3D container_of(head, struct page, rcu_head); + pte_free(NULL /* mm not passed and not used */, (pgtable_t)page); +} + +void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable) +{ + struct page *page; + + page =3D pgtable; + call_rcu(&page->rcu_head, pte_free_now); +} +#endif /* pte_free_defer */ #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ =20 #if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \ --=20 2.35.3