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Mon, 1 Dec 2025 17:47:44 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.66.60]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id A8ADC1800361; Mon, 1 Dec 2025 17:47:33 +0000 (UTC) From: Nico Pache To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Cc: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de Subject: [PATCH v13 mm-new 02/16] introduce collapse_single_pmd to unify khugepaged and madvise_collapse Date: Mon, 1 Dec 2025 10:46:13 -0700 Message-ID: <20251201174627.23295-3-npache@redhat.com> In-Reply-To: <20251201174627.23295-1-npache@redhat.com> References: <20251201174627.23295-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F34ED140011 X-Stat-Signature: ptts9sb3utgg96im7hm7o654paitwwzc X-Rspam-User: X-HE-Tag: 1764611271-424554 X-HE-Meta: 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 zbuxHBBk 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The khugepaged daemon and madvise_collapse have two different implementations that do almost the same thing. Create collapse_single_pmd to increase code reuse and create an entry point to these two users. Refactor madvise_collapse and collapse_scan_mm_slot to use the new collapse_single_pmd function. This introduces a minor behavioral change that is most likely an undiscovered bug. The current implementation of khugepaged tests collapse_test_exit_or_disable before calling collapse_pte_mapped_thp, but we weren't doing it in the madvise_collapse case. By unifying these two callers madvise_collapse now also performs this check. We also modify the return value to be SCAN_ANY_PROCESS which properly indicates that this process is no longer valid to operate on. We also guard the khugepaged_pages_collapsed variable to ensure its only incremented for khugepaged. Reviewed-by: Wei Yang Reviewed-by: Lance Yang Reviewed-by: Lorenzo Stoakes Reviewed-by: Baolin Wang Acked-by: David Hildenbrand Signed-off-by: Nico Pache --- mm/khugepaged.c | 97 ++++++++++++++++++++++++++----------------------- 1 file changed, 52 insertions(+), 45 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 959be77f2e65..433ea7283488 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2392,6 +2392,53 @@ static int collapse_scan_file(struct mm_struct *mm, unsigned long addr, return result; } +/* + * Try to collapse a single PMD starting at a PMD aligned addr, and return + * the results. + */ +static int collapse_single_pmd(unsigned long addr, + struct vm_area_struct *vma, bool *mmap_locked, + struct collapse_control *cc) +{ + struct mm_struct *mm = vma->vm_mm; + int result; + struct file *file; + pgoff_t pgoff; + + if (vma_is_anonymous(vma)) { + result = collapse_scan_pmd(mm, vma, addr, mmap_locked, cc); + goto end; + } + + file = get_file(vma->vm_file); + pgoff = linear_page_index(vma, addr); + + mmap_read_unlock(mm); + *mmap_locked = false; + result = collapse_scan_file(mm, addr, file, pgoff, cc); + fput(file); + if (result != SCAN_PTE_MAPPED_HUGEPAGE) + goto end; + + mmap_read_lock(mm); + *mmap_locked = true; + if (collapse_test_exit_or_disable(mm)) { + mmap_read_unlock(mm); + *mmap_locked = false; + return SCAN_ANY_PROCESS; + } + result = collapse_pte_mapped_thp(mm, addr, !cc->is_khugepaged); + if (result == SCAN_PMD_MAPPED) + result = SCAN_SUCCEED; + mmap_read_unlock(mm); + *mmap_locked = false; + +end: + if (cc->is_khugepaged && result == SCAN_SUCCEED) + ++khugepaged_pages_collapsed; + return result; +} + static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result, struct collapse_control *cc) __releases(&khugepaged_mm_lock) @@ -2462,34 +2509,9 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result, VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); - if (!vma_is_anonymous(vma)) { - struct file *file = get_file(vma->vm_file); - pgoff_t pgoff = linear_page_index(vma, - khugepaged_scan.address); - - mmap_read_unlock(mm); - mmap_locked = false; - *result = collapse_scan_file(mm, - khugepaged_scan.address, file, pgoff, cc); - fput(file); - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) { - mmap_read_lock(mm); - if (collapse_test_exit_or_disable(mm)) - goto breakouterloop; - *result = collapse_pte_mapped_thp(mm, - khugepaged_scan.address, false); - if (*result == SCAN_PMD_MAPPED) - *result = SCAN_SUCCEED; - mmap_read_unlock(mm); - } - } else { - *result = collapse_scan_pmd(mm, vma, - khugepaged_scan.address, &mmap_locked, cc); - } - - if (*result == SCAN_SUCCEED) - ++khugepaged_pages_collapsed; + *result = collapse_single_pmd(khugepaged_scan.address, + vma, &mmap_locked, cc); /* move to next address */ khugepaged_scan.address += HPAGE_PMD_SIZE; progress += HPAGE_PMD_NR; @@ -2801,35 +2823,20 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); } mmap_assert_locked(mm); - if (!vma_is_anonymous(vma)) { - struct file *file = get_file(vma->vm_file); - pgoff_t pgoff = linear_page_index(vma, addr); - mmap_read_unlock(mm); - mmap_locked = false; - result = collapse_scan_file(mm, addr, file, pgoff, cc); - fput(file); - } else { - result = collapse_scan_pmd(mm, vma, addr, - &mmap_locked, cc); - } + result = collapse_single_pmd(addr, vma, &mmap_locked, cc); + if (!mmap_locked) *lock_dropped = true; -handle_result: switch (result) { case SCAN_SUCCEED: case SCAN_PMD_MAPPED: ++thps; break; - case SCAN_PTE_MAPPED_HUGEPAGE: - BUG_ON(mmap_locked); - mmap_read_lock(mm); - result = collapse_pte_mapped_thp(mm, addr, true); - mmap_read_unlock(mm); - goto handle_result; /* Whitelisted set of results where continuing OK */ case SCAN_NO_PTE_TABLE: + case SCAN_PTE_MAPPED_HUGEPAGE: case SCAN_PTE_NON_PRESENT: case SCAN_PTE_UFFD_WP: case SCAN_LACK_REFERENCED_PAGE: -- 2.51.1