From patchwork Mon May 29 06:26:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hugh Dickins X-Patchwork-Id: 100095 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:994d:0:b0:3d9:f83d:47d9 with SMTP id k13csp1312603vqr; Sun, 28 May 2023 23:31:06 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ7bbKIQx+f29r4/p8oImYQMSjLLI3duFsNvz2sH53fSe9MRIBjKOmIHySbH3u/KKCIQZ+QK X-Received: by 2002:a17:90b:a57:b0:255:f01e:5aff with SMTP id gw23-20020a17090b0a5700b00255f01e5affmr9329455pjb.34.1685341866585; Sun, 28 May 2023 23:31:06 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1685341866; cv=none; d=google.com; s=arc-20160816; b=QJUdiAZKbImQi6yDqQ+bUzR63vYH4dSQyWHXOI4HzDFHsk3u1+7EVi9Bph130cH5Nu PkqFJyzvx4OI8QL187AYYhNjp/Uf7A9E1sOZQUuCU4hFiSd2ZZsH7O5dmPKrOzkcko4R Y9zheHMz+F9Si26O89NKXpiJ3OxnzpzfDeP3zYMkmhYWbMQi4xir/cr/h5ohwJ4z+h13 sHUibym+hppt3hkHiytTSZCCdytpRXzw7cpaSvHBwT+4BWOa0GheTd/OQ1/oftGJQZ+i 7EbwbUpVlHFyRCGvX8Bu+ULIIrAGPjvoGXk1T7zQg2CR2VxpernK4KPzFMU/j9ItC5x1 MPtw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:mime-version:references:message-id:in-reply-to :subject:cc:to:from:date:dkim-signature; bh=OPZMX1+LA/FvHP0/JC5qx50WzIWIXFewxM+MGzYgG4M=; b=DI8iKZZ+G2KJOtrQLMAOgTclfI3x1PvOvWW3lfcyqZ5SbXbnHLtbmM0YnZL90p3EXa A3DW31fqfoX2i7v4JoEN6vBghwFPI44P8fUlSa3ffE64bRjT/ldk+MagLup6M2GmA/O0 25sxgFionrE1C4UQRllgVcUHE7icgou/zauQsn7Ru/I9FqwFwUfLvcIhxL/Dz32+vZA4 o/WVPn2lrL4srFBrRofZks+qGAQRls8H6UTAqfxuehiiK8Q0NkJPw4jmGYSORmX69zRD PKF2PVnUHkBYXJKrI1aDvYCSy8pJbAn4DnVNo/C/sGu4LBG5IeVM+nGcONaK4FiVwtwJ mkWQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20221208 header.b=Ytf3pJx5; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id t5-20020a17090abc4500b00255813b0d96si3612876pjv.179.2023.05.28.23.30.54; Sun, 28 May 2023 23:31:06 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20221208 header.b=Ytf3pJx5; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231641AbjE2G1f (ORCPT + 99 others); Mon, 29 May 2023 02:27:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231682AbjE2G1X (ORCPT ); Mon, 29 May 2023 02:27:23 -0400 Received: from mail-yb1-xb2b.google.com (mail-yb1-xb2b.google.com [IPv6:2607:f8b0:4864:20::b2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 277FC19D for ; Sun, 28 May 2023 23:26:54 -0700 (PDT) Received: by mail-yb1-xb2b.google.com with SMTP id 3f1490d57ef6-ba8afcc82c0so5796215276.2 for ; Sun, 28 May 2023 23:26:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1685341612; x=1687933612; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to; bh=OPZMX1+LA/FvHP0/JC5qx50WzIWIXFewxM+MGzYgG4M=; b=Ytf3pJx5ZO2h8JphUMEUM+NgVIXTwIVhtYTQ/lA5Y8cir60w0OXuWtSllgiDhinPaR Iy4j/+CUvFlAp4R/CjSOblw5I+znP0kaNSqJXR4VKYKvTUfPb3oYvzoFoZFf0g3HTRPQ tAY4R1a5sWTcuBd7Oz6cpvBBwVDFmQiqte1C3YTUpMO9AoANcfZAyiW/btELN35Kv490 fFp3EQeG93PsokK2axn0N0nvmbnw91onFgB1MigUnnJSNnNJsoUz87zNfUFbsCL7jZ72 cyBArEZpOY67dIbt6WH+/9VlUHqVGsY29EI6EqLyGxDNiZ8V+VTllfG1NJsbPWUsuh6Y 4UjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685341612; x=1687933612; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=OPZMX1+LA/FvHP0/JC5qx50WzIWIXFewxM+MGzYgG4M=; b=dZArGuEZZl+0ysFdi2nbhzpjLv0XjuhXMFscP6iTLbC3XU2t024Y9mVhJA0ypDqTc0 dbryjS3bsYVA0IZhb97bQMNTS+Aby1y28s0zf/FhIv9fIjrbdwZe8xVcsG//C8id8ME6 ggw9dFkiTRIJqObLH44BvRlXW4K/1wyTWwMqGZv70P2AV1rWeej5cfltZVTRL+iKebdY j/hqs+P3qjJBrJbNuMbG4oYTmoNfNaz2eLvPpidR1yi/KKS4fGcdqBnC5hNpTTK2s4zp B4tnxGWfYDjxudJ9bisfNb+I2nlKWdlC1579D+B8KMuiF+U+rRdOanOw5mIffMk+102u 6z+A== X-Gm-Message-State: AC+VfDyjqqtqWWcNfcTH40pGMrvZErTqsOPiTXNXtcqw92vLUZXWhFIb 6ff3HA3imjT5hHpbcF5njAizAQ== X-Received: by 2002:a81:5b55:0:b0:565:ec67:18f4 with SMTP id p82-20020a815b55000000b00565ec6718f4mr4108617ywb.32.1685341612167; Sun, 28 May 2023 23:26:52 -0700 (PDT) Received: from ripple.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id m6-20020a0de306000000b0055a486140b6sm3427593ywe.36.2023.05.28.23.26.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 May 2023 23:26:51 -0700 (PDT) Date: Sun, 28 May 2023 23:26:48 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: 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 , 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 , 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 10/12] mm/khugepaged: collapse_pte_mapped_thp() with mmap_read_lock() In-Reply-To: <35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com> Message-ID: <563340a4-7ac9-7cc8-33d8-f7cc6ef19ea6@google.com> References: <35e983f5-7ed3-b310-d949-9ae8b130cdab@google.com> MIME-Version: 1.0 X-Spam-Status: No, score=-17.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, ENV_AND_HDR_SPF_MATCH,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE,USER_IN_DEF_DKIM_WL,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1767209033254041394?= X-GMAIL-MSGID: =?utf-8?q?1767209033254041394?= Bring collapse_and_free_pmd() back into collapse_pte_mapped_thp(). It does need mmap_read_lock(), but it does not need mmap_write_lock(), nor vma_start_write() nor i_mmap lock nor anon_vma lock. All racing paths are relying on pte_offset_map_lock() and pmd_lock(), so use those. Follow the pattern in retract_page_tables(); and using pte_free_defer() removes the need for tlb_remove_table_sync_one() here. Confirm the preliminary find_pmd_or_thp_or_none() once page lock has been acquired and the page looks suitable: from then on its state is stable. However, collapse_pte_mapped_thp() was doing something others don't: freeing a page table still containing "valid" entries. i_mmap lock did stop a racing truncate from double-freeing those pages, but we prefer collapse_pte_mapped_thp() to clear the entries as usual. Their TLB flush can wait until the pmdp_collapse_flush() which follows, but the mmu_notifier_invalidate_range_start() has to be done earlier. Some cleanup while rearranging: rename "count" to "nr_ptes"; and "step 2" does not need to duplicate the checks in "step 1". Signed-off-by: Hugh Dickins --- mm/khugepaged.c | 131 +++++++++++++++--------------------------------- 1 file changed, 41 insertions(+), 90 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 4fd408154692..2999500abdd5 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1485,7 +1485,7 @@ static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm, return ret; } -/* hpage must be locked, and mmap_lock must be held in write */ +/* hpage must be locked, and mmap_lock must be held */ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmdp, struct page *hpage) { @@ -1497,7 +1497,7 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr, }; VM_BUG_ON(!PageTransHuge(hpage)); - mmap_assert_write_locked(vma->vm_mm); + mmap_assert_locked(vma->vm_mm); if (do_set_pmd(&vmf, hpage)) return SCAN_FAIL; @@ -1506,48 +1506,6 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr, return SCAN_SUCCEED; } -/* - * A note about locking: - * Trying to take the page table spinlocks would be useless here because those - * are only used to synchronize: - * - * - modifying terminal entries (ones that point to a data page, not to another - * page table) - * - installing *new* non-terminal entries - * - * Instead, we need roughly the same kind of protection as free_pgtables() or - * mm_take_all_locks() (but only for a single VMA): - * The mmap lock together with this VMA's rmap locks covers all paths towards - * the page table entries we're messing with here, except for hardware page - * table walks and lockless_pages_from_mm(). - */ -static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long addr, pmd_t *pmdp) -{ - pmd_t pmd; - struct mmu_notifier_range range; - - mmap_assert_write_locked(mm); - if (vma->vm_file) - lockdep_assert_held_write(&vma->vm_file->f_mapping->i_mmap_rwsem); - /* - * All anon_vmas attached to the VMA have the same root and are - * therefore locked by the same lock. - */ - if (vma->anon_vma) - lockdep_assert_held_write(&vma->anon_vma->root->rwsem); - - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, addr, - addr + HPAGE_PMD_SIZE); - mmu_notifier_invalidate_range_start(&range); - pmd = pmdp_collapse_flush(vma, addr, pmdp); - tlb_remove_table_sync_one(); - mmu_notifier_invalidate_range_end(&range); - mm_dec_nr_ptes(mm); - page_table_check_pte_clear_range(mm, addr, pmd); - pte_free(mm, pmd_pgtable(pmd)); -} - /** * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at * address haddr. @@ -1563,16 +1521,17 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, bool install_pmd) { + struct mmu_notifier_range range; unsigned long haddr = addr & HPAGE_PMD_MASK; struct vm_area_struct *vma = vma_lookup(mm, haddr); struct page *hpage; pte_t *start_pte, *pte; - pmd_t *pmd; - spinlock_t *ptl; - int count = 0, result = SCAN_FAIL; + pmd_t *pmd, pgt_pmd; + spinlock_t *pml, *ptl; + int nr_ptes = 0, result = SCAN_FAIL; int i; - mmap_assert_write_locked(mm); + mmap_assert_locked(mm); /* Fast check before locking page if already PMD-mapped */ result = find_pmd_or_thp_or_none(mm, haddr, &pmd); @@ -1612,6 +1571,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, goto drop_hpage; } + result = find_pmd_or_thp_or_none(mm, haddr, &pmd); switch (result) { case SCAN_SUCCEED: break; @@ -1625,27 +1585,14 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, goto drop_hpage; } - /* Lock the vma before taking i_mmap and page table locks */ - vma_start_write(vma); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, + haddr, haddr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); - /* - * We need to lock the mapping so that from here on, only GUP-fast and - * hardware page walks can access the parts of the page tables that - * we're operating on. - * See collapse_and_free_pmd(). - */ - i_mmap_lock_write(vma->vm_file->f_mapping); - - /* - * This spinlock should be unnecessary: Nobody else should be accessing - * the page tables under spinlock protection here, only - * lockless_pages_from_mm() and the hardware page walker can access page - * tables while all the high-level locks are held in write mode. - */ result = SCAN_FAIL; start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); - if (!start_pte) - goto drop_immap; + if (!start_pte) /* mmap_lock + page lock should prevent this */ + goto abort; /* step 1: check all mapped PTEs are to the right huge page */ for (i = 0, addr = haddr, pte = start_pte; @@ -1671,40 +1618,44 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, */ if (hpage + i != page) goto abort; - count++; + nr_ptes++; } - /* step 2: adjust rmap */ + /* step 2: clear page table and adjust rmap */ for (i = 0, addr = haddr, pte = start_pte; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { - struct page *page; - if (pte_none(*pte)) continue; - page = vm_normal_page(vma, addr, *pte); - if (WARN_ON_ONCE(page && is_zone_device_page(page))) - goto abort; - page_remove_rmap(page, vma, false); + + /* Must clear entry, or a racing truncate may re-remove it */ + pte_clear(mm, addr, pte); + page_remove_rmap(hpage + i, vma, false); } pte_unmap_unlock(start_pte, ptl); /* step 3: set proper refcount and mm_counters. */ - if (count) { - page_ref_sub(hpage, count); - add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); + if (nr_ptes) { + page_ref_sub(hpage, nr_ptes); + add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -nr_ptes); } - /* step 4: remove pte entries */ - /* we make no change to anon, but protect concurrent anon page lookup */ - if (vma->anon_vma) - anon_vma_lock_write(vma->anon_vma); + /* step 4: remove page table */ - collapse_and_free_pmd(mm, vma, haddr, pmd); + /* Huge page lock is still held, so page table must remain empty */ + pml = pmd_lock(mm, pmd); + if (ptl != pml) + spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); + pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); + if (ptl != pml) + spin_unlock(ptl); + spin_unlock(pml); - if (vma->anon_vma) - anon_vma_unlock_write(vma->anon_vma); - i_mmap_unlock_write(vma->vm_file->f_mapping); + mmu_notifier_invalidate_range_end(&range); + + mm_dec_nr_ptes(mm); + page_table_check_pte_clear_range(mm, haddr, pgt_pmd); + pte_free_defer(mm, pmd_pgtable(pgt_pmd)); maybe_install_pmd: /* step 5: install pmd entry */ @@ -1718,9 +1669,9 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, return result; abort: - pte_unmap_unlock(start_pte, ptl); -drop_immap: - i_mmap_unlock_write(vma->vm_file->f_mapping); + if (start_pte) + pte_unmap_unlock(start_pte, ptl); + mmu_notifier_invalidate_range_end(&range); goto drop_hpage; } @@ -2842,9 +2793,9 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev, case SCAN_PTE_MAPPED_HUGEPAGE: BUG_ON(mmap_locked); BUG_ON(*prev); - mmap_write_lock(mm); + mmap_read_lock(mm); result = collapse_pte_mapped_thp(mm, addr, true); - mmap_write_unlock(mm); + mmap_locked = true; goto handle_result; /* Whitelisted set of results where continuing OK */ case SCAN_PMD_NULL: