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AJvYcCWDkq4HYsTr7qqjhyyG+kZXcxua34VKWAtnj9LgjDxU2wTE3purDH+6Icxp0gsuc/G7iY8aYlDrlbX84iortZEnnzYP/DZR5p2QPlCF X-Gm-Message-State: AOJu0YxNwxNmmA2CiFZUQmLJ1/Wd5SwbmdA6PJuH4ZdLywi551VFWO+g 1hUFBRVK9ojS4kQFqLykk7mjy5wxOzAt5Mq/fX6X0DNIEzthpKOC X-Google-Smtp-Source: AGHT+IHNlRE9Ql30bKl4wf8mPivbg9Uu62KGA61WCjKuW56gBBFvSattqBS4RrJD3TWyboPzl/3vNg== X-Received: by 2002:a17:902:d2cf:b0:1f3:dd7:ad42 with SMTP id d9443c01a7336-1f30dd7af64mr10263255ad.0.1716264214253; Mon, 20 May 2024 21:03:34 -0700 (PDT) Received: from LancedeMBP.lan.lan ([2403:2c80:6::302d]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1ef0bad62bfsm211683945ad.74.2024.05.20.21.03.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 May 2024 21:03:33 -0700 (PDT) From: Lance Yang To: akpm@linux-foundation.org Cc: willy@infradead.org, sj@kernel.org, baolin.wang@linux.alibaba.com, maskray@google.com, ziy@nvidia.com, ryan.roberts@arm.com, david@redhat.com, 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, libang.li@antgroup.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lance Yang Subject: [PATCH v6 2/3] mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop Date: Tue, 21 May 2024 12:02:43 +0800 Message-Id: <20240521040244.48760-3-ioworker0@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20240521040244.48760-1-ioworker0@gmail.com> References: <20240521040244.48760-1-ioworker0@gmail.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="utf-8" Content-Transfer-Encoding: quoted-printable In preparation for supporting try_to_unmap_one() to unmap PMD-mapped folios, start the pagewalk first, then call split_huge_pmd_address() to split the folio. Since TTU_SPLIT_HUGE_PMD will no longer perform immediately, we might encounter a PMD-mapped THP missing the mlock in the VM_LOCKED range during the page walk. It=E2=80=99s probably necessary to mlock this THP to prevent= it from being picked up during page reclaim. Suggested-by: David Hildenbrand Suggested-by: Baolin Wang Signed-off-by: Lance Yang --- include/linux/huge_mm.h | 6 ++++++ mm/huge_memory.c | 42 +++++++++++++++++++++-------------------- mm/rmap.c | 26 ++++++++++++++++++------- 3 files changed, 47 insertions(+), 27 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index c8d3ec116e29..9fcb0b0b6ed1 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -409,6 +409,9 @@ static inline bool thp_migration_supported(void) return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION); } =20 +void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addre= ss, + pmd_t *pmd, bool freeze, struct folio *folio); + #else /* CONFIG_TRANSPARENT_HUGEPAGE */ =20 static inline bool folio_test_pmd_mappable(struct folio *folio) @@ -471,6 +474,9 @@ static inline void __split_huge_pmd(struct vm_area_stru= ct *vma, pmd_t *pmd, unsigned long address, bool freeze, struct folio *folio) {} static inline void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, bool freeze, struct folio *folio) {} +static inline void split_huge_pmd_locked(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, + bool freeze, struct folio *folio) {} =20 #define split_huge_pud(__vma, __pmd, __address) \ do { } while (0) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 317de2afd371..425272c6c50b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2581,6 +2581,27 @@ static void __split_huge_pmd_locked(struct vm_area_s= truct *vma, pmd_t *pmd, pmd_populate(mm, pmd, pgtable); } =20 +void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addre= ss, + pmd_t *pmd, bool freeze, struct folio *folio) +{ + VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio)); + VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); + VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); + VM_BUG_ON(freeze && !folio); + + /* + * When the caller requests to set up a migration entry, we + * require a folio to check the PMD against. Otherwise, there + * is a risk of replacing the wrong folio. + */ + if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || + is_pmd_migration_entry(*pmd)) { + if (folio && folio !=3D pmd_folio(*pmd)) + return; + __split_huge_pmd_locked(vma, pmd, address, freeze); + } +} + void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long address, bool freeze, struct folio *folio) { @@ -2592,26 +2613,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pm= d_t *pmd, (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); ptl =3D pmd_lock(vma->vm_mm, pmd); - - /* - * If caller asks to setup a migration entry, we need a folio to check - * pmd against. Otherwise we can end up replacing wrong folio. - */ - VM_BUG_ON(freeze && !folio); - VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); - - if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || - is_pmd_migration_entry(*pmd)) { - /* - * It's safe to call pmd_page when folio is set because it's - * guaranteed that pmd is present. - */ - if (folio && folio !=3D pmd_folio(*pmd)) - goto out; - __split_huge_pmd_locked(vma, pmd, range.start, freeze); - } - -out: + split_huge_pmd_locked(vma, range.start, pmd, freeze, folio); spin_unlock(ptl); mmu_notifier_invalidate_range_end(&range); } diff --git a/mm/rmap.c b/mm/rmap.c index ddffa30c79fb..08a93347f283 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1640,9 +1640,6 @@ static bool try_to_unmap_one(struct folio *folio, str= uct vm_area_struct *vma, if (flags & TTU_SYNC) pvmw.flags =3D PVMW_SYNC; =20 - if (flags & TTU_SPLIT_HUGE_PMD) - split_huge_pmd_address(vma, address, false, folio); - /* * For THP, we have to assume the worse case ie pmd for invalidation. * For hugetlb, it could be much worse if we need to do pud @@ -1668,20 +1665,35 @@ static bool try_to_unmap_one(struct folio *folio, s= truct vm_area_struct *vma, mmu_notifier_invalidate_range_start(&range); =20 while (page_vma_mapped_walk(&pvmw)) { - /* Unexpected PMD-mapped THP? */ - VM_BUG_ON_FOLIO(!pvmw.pte, folio); - /* * If the folio is in an mlock()d vma, we must not swap it out. */ if (!(flags & TTU_IGNORE_MLOCK) && (vma->vm_flags & VM_LOCKED)) { /* Restore the mlock which got missed */ - if (!folio_test_large(folio)) + if (!folio_test_large(folio) || + (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD))) mlock_vma_folio(folio, vma); goto walk_done_err; } =20 + if (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)) { + /* + * We temporarily have to drop the PTL and start once + * again from that now-PTE-mapped page table. + */ + split_huge_pmd_locked(vma, range.start, pvmw.pmd, false, + folio); + pvmw.pmd =3D NULL; + spin_unlock(pvmw.ptl); + pvmw.ptl =3D NULL; + flags &=3D ~TTU_SPLIT_HUGE_PMD; + continue; + } + + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_FOLIO(!pvmw.pte, folio); + pfn =3D pte_pfn(ptep_get(pvmw.pte)); subpage =3D folio_page(folio, pfn - folio_pfn(folio)); address =3D pvmw.address; --=20 2.33.1