From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A2FC39E6ED for ; Thu, 26 Feb 2026 09:23:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772097837; cv=none; b=ktchC8zE/QoUKnRVJ8OxbZlJFRHU4jnzNSXUqybER9DE2z2kMsLbrv2Z9gl4WLeq/AfcYmyX5sg+0xaxmk6wyA6Ia5ugs4LNCtOPNMN+InCf6zPv4/9U/zDpA3G5Vo9+Nbnt3u0pRA6yq6OzSkC0M5bbMuzZKumfh6EtW2Dldvk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772097837; c=relaxed/simple; bh=Y86Da6+jroLDcvQEnhJbEp7MSTRTesBQMo6Mg6g8RIc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=M6jQMvL6DzPJZ+v+e6gADFAvbv/M489byropSqTLs7FFF6HmXfOTssD3UBDZ2B1yAqb0VN4yC2ou0gPfBX5E2QICmZl36BImcFWzluO1gtKhOAhXnuyTi1ln8D9DXj3CpqqsIIv13e7AZ6j4sz08Re1TB2k8Od6SI47EbNX/heg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=Aedp18hm; arc=none smtp.client-ip=115.124.30.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="Aedp18hm" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1772097833; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=NMIGcQmXL6bNGpLRZlwetHCCNpKRzFWWcdjC2dOpFyk=; b=Aedp18hmZRP6wshK9/41MrJBBoKPMxTKKFuq9lKzcLW+7XjNHyuU+QVeS4cWuQpVaw1lntKl5Ivk9JxY1w7yLsPDDTiA2AceV4VlX0Pqv8kNX6dj2IPk9FJUhdKQPx/WWSjz0OPsPp5o2YbMCye8+YqNkZE/zrtC3bPRkPggWOM= Received: from 30.74.144.118(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Wzqqw9q_1772097828 cluster:ay36) by smtp.aliyun-inc.com; Thu, 26 Feb 2026 17:23:50 +0800 Message-ID: <60e44957-b816-4f7e-b004-4e957a67fe12@linux.alibaba.com> Date: Thu, 26 Feb 2026 17:23:48 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v2 5/5] mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() To: Nico Pache , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260226012929.169479-1-npache@redhat.com> <20260226012929.169479-6-npache@redhat.com> From: Baolin Wang In-Reply-To: <20260226012929.169479-6-npache@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/26/26 9:29 AM, Nico Pache wrote: > 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: Lorenzo Stoakes > Signed-off-by: Nico Pache > --- [snip] > for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { > enum scan_result result = SCAN_FAIL; > - bool triggered_wb = false; > > -retry: > if (!mmap_locked) { > cond_resched(); > mmap_read_lock(mm); > mmap_locked = true; > + *lock_dropped = true; IIUC, this should be '*lock_dropped = false', right? > result = hugepage_vma_revalidate(mm, addr, false, &vma, > cc); > if (result != SCAN_SUCCEED) { > @@ -2836,46 +2872,20 @@ 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; > - *lock_dropped = true; > - result = collapse_scan_file(mm, addr, file, pgoff, NULL, cc); > > - if (result == SCAN_PAGE_DIRTY_OR_WRITEBACK && !triggered_wb && > - mapping_can_writeback(file->f_mapping)) { > - loff_t lstart = (loff_t)pgoff << PAGE_SHIFT; > - loff_t lend = lstart + HPAGE_PMD_SIZE - 1; > + result = collapse_single_pmd(addr, vma, &mmap_locked, NULL, cc); > > - filemap_write_and_wait_range(file->f_mapping, lstart, lend); > - triggered_wb = true; > - fput(file); > - goto retry; > - } > - fput(file); > - } else { > - result = collapse_scan_pmd(mm, vma, addr, &mmap_locked, NULL, 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: