From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9E463C88E64 for ; Mon, 14 Sep 2026 11:44:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 932AD6B00A6; Mon, 14 Sep 2026 07:44:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 90B126B00A7; Mon, 14 Sep 2026 07:44:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7AD226B00A9; Mon, 14 Sep 2026 07:44:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 4B8D56B00A6 for ; Mon, 14 Sep 2026 07:44:15 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C203E1C20F0 for ; Mon, 14 Sep 2026 11:44:14 +0000 (UTC) X-FDA: 85212184428.16.05D6A92 Received: from mta0.migadu.com (out-196.mta0.migadu.com [91.218.175.196]) by imf27.hostedemail.com (Postfix) with ESMTP id D44DD40006 for ; Mon, 14 Sep 2026 11:44:12 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=fhoa6ZtX; spf=pass (imf27.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.196 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789386253; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=q+wLh7Uo2d1l8gn3sY24WPKPqtbphkGZ7ajT06ObVxc=; b=wd3XflAT9cAByF3YzNqFdM2rLiP20hTPW60ScxU0wD60u92dOIiOWHJ0iJk4Y8VeIbiZ+q q4GTc5w3RB7nz9g2mD7N/S1CfkilUdqKZUiy4mqEByqB+PZKLHn8WOiCESN4DTO4HPcxnI ONqDwTRmR7nANM0W09uNLaJttPl+8Y8= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789386253; b=WvZwRF95olhdvjYVo++n2i0DSBsgJTjZLR5dVz3N+WwfaNJnpRQ+zm1xuDxaCMZUeWFt/f aPz8aXD9GeZgCBR/DQ1xKW/YhSM2BH286nKODZPrJ47zSfLTUAYVzPP2Y4k6L7qzA4grjc ApxtJJsC8TnlpeyyZEF8ubTgNZVAIHc= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=fhoa6ZtX; spf=pass (imf27.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.196 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Envelope-To: linux-mm@kvack.org DKIM-Signature: a=rsa-sha256; bh=3XNEzeVU1O8SWrgui6NV2H1NKonCjPLxXmf/sJyhnNo=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789386251; v=1; x=1789991051; b=fhoa6ZtXOauQMJgnFoXqVJ0U7Maq+6jnRpScN7TqyW8epwl29fE3cqpav4sJIlpaCQ3x/xuh 0KpTJmykCC4RhnYev8sO2Bf3FtxBPAEhCh/UqUfcyl5/YXUUgYLp0uDmTni1z7rtD6cJVqhiHXm C5c6hRkB5tt4RH73ews4gdzc= X-Envelope-To: linux-mm@kvack.org Received: by mta12.migadu.com with ESMTPS id 1460ad6acf0457ca; Mon, 14 Sep 2026 11:44:11 +0000 X-Mizu-Trace-ID: 1460ad6acf0457ca X-Migadu-Flow: FLOW_OUT From: Usama Arif To: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org Cc: ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , Liam R. Howlett , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Usama Arif Subject: [PATCH v7 10/29] mm: make PMD migration-entry splitting explicit Date: Mon, 14 Sep 2026 04:42:02 -0700 Message-ID: <20260914114320.12988-11-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914114320.12988-1-usama.arif@linux.dev> References: <20260914114320.12988-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D44DD40006 X-Stat-Signature: zorwz913p6q5zrecmto7z8q5odt3s33d X-Rspam-User: X-HE-Tag: 1789386252-201697 X-HE-Meta: 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 EATz8lI6 HOYDpHw+uPE800oDvogB1X38jVOUZaCkBLmHA6orO38BTX1sCo1jvvcPuHfHSACgFuki1Rq7A6/dzDtp7mJmpGt0rPMIMUyiYoWx+7pNvqTP+a4EML3dM/C5Dtgb/sk40Q2XyNpZhKtP4sQDL87rovgD3HE14Xo+omTKI/Z22bE6sMnuuYddfyseNoI83eNVRzpl8ohsm0eD/OhmeYAeocgA8lo/tWgaV03WITV4ok7uN0QOkPAKlYt8SG7pzV2Hfkw35 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: __split_huge_pmd() and friends take a "freeze" boolean that every caller has to pass and almost every caller passes as false. The name says nothing about what it selects, and the one thing it does select - PTE migration entries instead of PTE mappings - is only ever wanted by the rmap migration path. Rename it to use_migration_entries, keep it private to mm/huge_memory.c, and add split_pmd_to_migration_entries() for try_to_migrate_one(), the only caller that wants it. migrate_vma_split_unmapped_folio() also passed freeze=true, but only ever runs on a PMD that is already a migration entry, which the generic helper expands into PTE migration entries either way. Its folio_get() only existed to balance the put_page() that freeze=true performs, so both go. No functional change intended. Suggested-by: David Hildenbrand (Arm) Signed-off-by: Usama Arif --- include/linux/huge_mm.h | 22 ++++++++------- mm/huge_memory.c | 60 ++++++++++++++++++++++++----------------- mm/memory.c | 4 +-- mm/migrate_device.c | 7 +---- mm/mprotect.c | 2 +- mm/rmap.c | 7 +++-- 6 files changed, 55 insertions(+), 47 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 8ca0fa3be2acb..64b6a2eea899d 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -430,7 +430,7 @@ int folio_memcg_alloc_deferred(struct folio *folio); void deferred_split_folio(struct folio *folio, bool partially_mapped); void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address, bool freeze); + unsigned long address); /** * pmd_is_huge() - Is this PMD either a huge PMD entry or a software leaf entry? @@ -462,12 +462,10 @@ static inline bool pmd_is_huge(pmd_t pmd) do { \ pmd_t *____pmd = (__pmd); \ if (pmd_is_huge(*____pmd)) \ - __split_huge_pmd(__vma, __pmd, __address, \ - false); \ + __split_huge_pmd(__vma, __pmd, __address); \ } while (0) -void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, - bool freeze); +void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address); void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, unsigned long address); @@ -590,7 +588,9 @@ static inline bool thp_migration_supported(void) } void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, - pmd_t *pmd, bool freeze); + pmd_t *pmd); +void split_pmd_to_migration_entries(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd); bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp, struct folio *folio); void map_anon_folio_pmd_nopf(struct folio *folio, pmd_t *pmd, @@ -690,12 +690,14 @@ static inline void deferred_split_folio(struct folio *folio, bool partially_mapp do { } while (0) static inline void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address, bool freeze) {} + unsigned long address) {} static inline void split_huge_pmd_address(struct vm_area_struct *vma, - unsigned long address, bool freeze) {} + unsigned long address) {} static inline void split_huge_pmd_locked(struct vm_area_struct *vma, - unsigned long address, pmd_t *pmd, - bool freeze) {} + unsigned long address, pmd_t *pmd) {} +static inline void +split_pmd_to_migration_entries(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd) {} static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ee8d46827ffdc..873887aed0bc2 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2033,7 +2033,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte_free(dst_mm, pgtable); spin_unlock(src_ptl); spin_unlock(dst_ptl); - __split_huge_pmd(src_vma, src_pmd, addr, false); + __split_huge_pmd(src_vma, src_pmd, addr); return -EAGAIN; } add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); @@ -2257,7 +2257,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) folio_unlock(folio); spin_unlock(vmf->ptl); fallback: - __split_huge_pmd(vma, vmf->pmd, vmf->address, false); + __split_huge_pmd(vma, vmf->pmd, vmf->address); return VM_FAULT_FALLBACK; } @@ -3190,7 +3190,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, } static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long haddr, bool freeze) + unsigned long haddr, bool use_migration_entries) { struct mm_struct *mm = vma->vm_mm; struct folio *folio; @@ -3291,10 +3291,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, * folios w.r.t anon exclusive handling. See the comments for * folio handling and anon_exclusive below. */ - if (freeze && anon_exclusive && + if (use_migration_entries && anon_exclusive && folio_try_share_anon_rmap_pmd(folio, page)) - freeze = false; - if (!freeze) { + use_migration_entries = false; + if (!use_migration_entries) { rmap_t rmap_flags = RMAP_NONE; folio_ref_add(folio, HPAGE_PMD_NR - 1); @@ -3344,11 +3344,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); /* - * Without "freeze", we'll simply split the PMD, propagating the - * PageAnonExclusive() flag for each PTE by setting it for + * Without migration entries, we'll simply split the PMD and + * propagate the PageAnonExclusive() flag for each PTE by setting it for * each subpage -- no need to (temporarily) clear. * - * With "freeze" we want to replace mapped pages by + * With migration entries we want to replace mapped pages by * migration entries right away. This is only possible if we * managed to clear PageAnonExclusive() -- see * set_pmd_migration_entry(). @@ -3359,10 +3359,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, * See folio_try_share_anon_rmap_pmd(): invalidate PMD first. */ anon_exclusive = PageAnonExclusive(page); - if (freeze && anon_exclusive && + if (use_migration_entries && anon_exclusive && folio_try_share_anon_rmap_pmd(folio, page)) - freeze = false; - if (!freeze) { + use_migration_entries = false; + if (!use_migration_entries) { rmap_t rmap_flags = RMAP_NONE; folio_ref_add(folio, HPAGE_PMD_NR - 1); @@ -3387,7 +3387,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, * Note that NUMA hinting access restrictions are not transferred to * avoid any possibility of altering permissions across VMAs. */ - if (freeze || pmd_is_migration_entry(old_pmd)) { + if (use_migration_entries || pmd_is_migration_entry(old_pmd)) { pte_t entry; swp_entry_t swp_entry; @@ -3420,8 +3420,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { /* * anon_exclusive was already propagated to the relevant - * pages corresponding to the pte entries when freeze - * is false. + * pages corresponding to the pte entries when + * use_migration_entries is false. */ if (write) swp_entry = make_writable_device_private_entry( @@ -3469,7 +3469,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, if (!pmd_is_migration_entry(*pmd)) folio_remove_rmap_pmd(folio, page, vma); - if (freeze) + if (use_migration_entries) put_page(page); smp_wmb(); /* make pte visible before pmd */ @@ -3477,15 +3477,28 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, } void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, - pmd_t *pmd, bool freeze) + pmd_t *pmd) { VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); if (pmd_trans_huge(*pmd) || pmd_is_valid_softleaf(*pmd)) - __split_huge_pmd_locked(vma, pmd, address, freeze); + __split_huge_pmd_locked(vma, pmd, address, false); +} + +/* + * Split a present PMD into PTE migration entries, for the rmap migration + * walker. Like split_huge_pmd_locked(), the caller must hold the PMD lock and + * must already be inside an mmu_notifier invalidate range. + */ +void split_pmd_to_migration_entries(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd) +{ + VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); + if (pmd_trans_huge(*pmd) || pmd_is_valid_softleaf(*pmd)) + __split_huge_pmd_locked(vma, pmd, address, true); } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address, bool freeze) + unsigned long address) { spinlock_t *ptl; struct mmu_notifier_range range; @@ -3495,20 +3508,19 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); ptl = pmd_lock(vma->vm_mm, pmd); - split_huge_pmd_locked(vma, range.start, pmd, freeze); + split_huge_pmd_locked(vma, range.start, pmd); spin_unlock(ptl); mmu_notifier_invalidate_range_end(&range); } -void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, - bool freeze) +void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address) { pmd_t *pmd = mm_find_pmd(vma->vm_mm, address); if (!pmd) return; - __split_huge_pmd(vma, pmd, address, freeze); + __split_huge_pmd(vma, pmd, address); } static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address) @@ -3520,7 +3532,7 @@ static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) && range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE), ALIGN(address, HPAGE_PMD_SIZE))) - split_huge_pmd_address(vma, address, false); + split_huge_pmd_address(vma, address); } void vma_adjust_trans_huge(struct vm_area_struct *vma, diff --git a/mm/memory.c b/mm/memory.c index 926276d419202..477d7e359b447 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2096,7 +2096,7 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, next = pmd_addr_end(addr, end); if (pmd_is_huge(*pmd)) { if (next - addr != HPAGE_PMD_SIZE) - __split_huge_pmd(vma, pmd, addr, false); + __split_huge_pmd(vma, pmd, addr); else if (zap_huge_pmd(tlb, vma, pmd, addr)) { addr = next; continue; @@ -6382,7 +6382,7 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf) split: /* COW or write-notify handled on pte level: split pmd. */ - __split_huge_pmd(vma, vmf->pmd, vmf->address, false); + __split_huge_pmd(vma, vmf->pmd, vmf->address); return VM_FAULT_FALLBACK; } diff --git a/mm/migrate_device.c b/mm/migrate_device.c index 0c437004329d9..4a0b61d50d222 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -918,12 +918,7 @@ static int migrate_vma_split_unmapped_folio(struct migrate_vma *migrate, unsigned long flags; int ret = 0; - /* - * take a reference, since split_huge_pmd_address() with freeze = true - * drops a reference at the end. - */ - folio_get(folio); - split_huge_pmd_address(migrate->vma, addr, true); + split_huge_pmd_address(migrate->vma, addr); ret = folio_split_unmapped(folio, 0); if (ret) return ret; diff --git a/mm/mprotect.c b/mm/mprotect.c index 2888ee638d872..ee33bbb421008 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -530,7 +530,7 @@ static inline long change_pmd_range(struct mmu_gather *tlb, if (pmd_is_huge(_pmd)) { if ((next - addr != HPAGE_PMD_SIZE) || pgtable_split_needed(vma, cp_flags)) { - __split_huge_pmd(vma, pmd, addr, false); + __split_huge_pmd(vma, pmd, addr); /* * For file-backed, the pmd could have been * cleared; make sure pmd populated if diff --git a/mm/rmap.c b/mm/rmap.c index 5332c52909be1..feb751e29b992 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2290,7 +2290,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * restart so we can process the PTE-mapped THP. */ split_huge_pmd_locked(vma, pvmw.address, - pvmw.pmd, false); + pvmw.pmd); flags &= ~TTU_SPLIT_HUGE_PMD; page_vma_mapped_walk_restart(&pvmw); continue; @@ -2515,13 +2515,12 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, if (flags & TTU_SPLIT_HUGE_PMD) { /* - * split_huge_pmd_locked() might leave the + * split_pmd_to_migration_entries() might leave the * folio mapped through PTEs. Retry the walk * so we can detect this scenario and properly * abort the walk. */ - split_huge_pmd_locked(vma, pvmw.address, - pvmw.pmd, true); + split_pmd_to_migration_entries(vma, pvmw.address, pvmw.pmd); flags &= ~TTU_SPLIT_HUGE_PMD; page_vma_mapped_walk_restart(&pvmw); continue; -- 2.53.0-Meta