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Thu, 11 Sep 2025 23:29:44 -0400 X-MC-Unique: DbG21aV7NumJcjM1VAnbGg-1 X-Mimecast-MFC-AGG-ID: DbG21aV7NumJcjM1VAnbGg_1757647780 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0D4F81955E9A; Fri, 12 Sep 2025 03:29:39 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.80.28]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 29C631800576; Fri, 12 Sep 2025 03:29:28 +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: 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 v11 02/15] introduce collapse_single_pmd to unify khugepaged and madvise_collapse Date: Thu, 11 Sep 2025 21:27:57 -0600 Message-ID: <20250912032810.197475-3-npache@redhat.com> In-Reply-To: <20250912032810.197475-1-npache@redhat.com> References: <20250912032810.197475-1-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-Queue-Id: 90CAB1C0012 X-Stat-Signature: safu793iq8ep13dw6echpskxddc1jp7e X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1757647788-756946 X-HE-Meta: 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 QlPyeKXe nJqKDklYzZtOU/6pccu6Ltn9VIGzieGrbRvvqTPwp+Imw091wcvzs2N61OT7rYu2IuPqADeeXZKNRtx0Jt98xHU/hbzNOAKwbu9DTFs9jmEbiXXdDbchZ+FfuCYTwibz6OOPa1UTPC5vEDmg7OUzZtOxBpzlkYEJip4fxgbvJGEGLVpKGORvmr4yv8Yhk3dzryjHJTyLMcigFirH6XllPd2o/4q3+0XPWjrgrmdyx/c6VaeWD1fbrRY72nQLcQaDlZVHFiukO5OV0Od75jSAiC9HQnsSN4fa5FpFwRzGgXL0HwQPa1OpQMBWS8YSa5s1fu6jV6gzRCF7PjDyFVxGEdVOmKWfLc4Le7NMahmZfEw3lGYiOwIAXEdAnAQNfv6NEVc5CeHeaPUcEZw2uKWRNOCOF6Ef2kOJ9wNp7RM7TRnbodLa5t5MXVRb7soMCvTEq/G0RZTTRMJxLsCYCnhaufc8FFgWFC8rOn7Te 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 40fa6e0a6b2d..63d2ba4b2b6d 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) @@ -2443,34 +2490,9 @@ 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; @@ -2786,34 +2808,19 @@ 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