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Wed, 22 Oct 2025 14:38:46 -0400 X-MC-Unique: 9BxQdaYtNci1k4WsNv73TA-1 X-Mimecast-MFC-AGG-ID: 9BxQdaYtNci1k4WsNv73TA_1761158320 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 568D51955EC8; Wed, 22 Oct 2025 18:38:38 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.41]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B979619560A2; Wed, 22 Oct 2025 18:38:27 +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 v12 mm-new 02/15] introduce collapse_single_pmd to unify khugepaged and madvise_collapse Date: Wed, 22 Oct 2025 12:37:04 -0600 Message-ID: <20251022183717.70829-3-npache@redhat.com> In-Reply-To: <20251022183717.70829-1-npache@redhat.com> References: <20251022183717.70829-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Stat-Signature: ar4z7cpp8jqyg6hr1s4e3ueni3ktznx9 X-Rspamd-Queue-Id: 92CDC160013 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761158331-477486 X-HE-Meta: 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 /tJpvq2q iuez7qOy7tCiGQ/KW5mvX0qDAjNn4bmVGKcaXpkVJ2aZebmrdThRxl03rVVTa+PZDx0tQ3wGnWOorYiGe6n+IV0vumMD4e8Jy6JYJsGcCeb9auqqa5ufZpXigL4cjf74RqYdP6gERN/HDnYxBwKtvHhD6p9Phtn+WQVPqIkEehaYyjUUEvtnz7aQvSbaDbKNF1eBywC9SJpUGlWx3GaWQH0U2GT3M4wNZ0bKmvj4x+eiRUgnTeGOUlCjaQw0rOn9gFbirZgQqZIoTmorWqwibW+eYaSTFqatAoJhQLyr9oSyyA5ivXzi0Q/dJmhONBE8zn3iQW4d/B7OQ0wUVeQ7G0s9HBV8xpj3Pula6BZHoDuEdhtfffust8yKfl/ABYDmHwjOD4LL9D+fwfbp7kf0xmKoDpyN7jW938ygxzMiiVFxnonPRxA68+D39m+ljWPpUqX8JG4mZX+GyHLkX/A5VYjHHtEV8X+AtIRVO 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: 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 6c4abc7f45cf..36e31d99e507 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2370,6 +2370,53 @@ 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) @@ -2440,34 +2487,9 @@ 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; @@ -2781,34 +2803,19 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, mmap_assert_locked(mm); memset(cc->node_load, 0, sizeof(cc->node_load)); nodes_clear(cc->alloc_nmask); - 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_PTE_MAPPED_HUGEPAGE: case SCAN_PMD_NULL: case SCAN_PTE_NON_PRESENT: case SCAN_PTE_UFFD_WP: -- 2.51.0