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Thu, 22 Jan 2026 19:30:33 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.88.59]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D87431958DC3; Thu, 22 Jan 2026 19:30:23 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: npache@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.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, zokeefe@google.com, rientjes@google.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, David Hildenbrand Subject: [PATCH mm-unstable v14 03/16] introduce collapse_single_pmd to unify khugepaged and madvise_collapse Date: Thu, 22 Jan 2026 12:28:28 -0700 Message-ID: <20260122192841.128719-4-npache@redhat.com> In-Reply-To: <20260122192841.128719-1-npache@redhat.com> References: <20260122192841.128719-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: O6FKmldCQnV6go4ycXZltaz2ab6M3yYV5r1Am9NmSyU_1769110234 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: 9yoqxf79m6zqgosz57az3r98s4paob1o X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A49A3180008 X-HE-Tag: 1769110248-277500 X-HE-Meta: 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 PQNe88v8 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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 Reviewed-by: Zi Yan Acked-by: David Hildenbrand Signed-off-by: Nico Pache --- mm/khugepaged.c | 106 +++++++++++++++++++++++++++--------------------- 1 file changed, 60 insertions(+), 46 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index fefcbdca4510..59e5a5588d85 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2394,6 +2394,54 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, unsigned long a return result; } +/* + * Try to collapse a single PMD starting at a PMD aligned addr, and return + * the results. + */ +static enum scan_result 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; + enum scan_result 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 = try_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, enum scan_result *result, struct collapse_control *cc) __releases(&khugepaged_mm_lock) @@ -2466,34 +2514,9 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, enum scan_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 = try_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; @@ -2799,6 +2822,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, cond_resched(); mmap_read_lock(mm); mmap_locked = true; + *lock_dropped = true; result = hugepage_vma_revalidate(mm, addr, false, &vma, cc); if (result != SCAN_SUCCEED) { @@ -2809,17 +2833,17 @@ 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_single_pmd(addr, vma, &mmap_locked, cc); + + if (!mmap_locked) *lock_dropped = true; - result = collapse_scan_file(mm, addr, file, pgoff, cc); - if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb && - mapping_can_writeback(file->f_mapping)) { + if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb) { + struct file *file = get_file(vma->vm_file); + pgoff_t pgoff = linear_page_index(vma, addr); + + if (mapping_can_writeback(file->f_mapping)) { loff_t lstart = (loff_t)pgoff << PAGE_SHIFT; loff_t lend = lstart + HPAGE_PMD_SIZE - 1; @@ -2829,26 +2853,16 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, goto retry; } fput(file); - } else { - result = collapse_scan_pmd(mm, vma, addr, &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 = try_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: -- 2.52.0