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Thu, 26 Feb 2026 01:31:32 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.173]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1CB903003D91; Thu, 26 Feb 2026 01:31:21 +0000 (UTC) From: Nico Pache To: 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, baolin.wang@linux.alibaba.com, 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, npache@redhat.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 Subject: [PATCH mm-unstable v2 5/5] mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() Date: Wed, 25 Feb 2026 18:29:29 -0700 Message-ID: <20260226012929.169479-6-npache@redhat.com> In-Reply-To: <20260226012929.169479-1-npache@redhat.com> References: <20260226012929.169479-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: Hc91JIuEyH-rSpn-eclnbcjDOy3E8qgLemprGzRcCec_1772069493 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Server: rspam05 X-Rspam-User: X-Rspamd-Queue-Id: 95059120007 X-Stat-Signature: m55wjzdw59isqkzed5aqh5yepkg5xizi X-HE-Tag: 1772069501-391888 X-HE-Meta: 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 DlqdTWjK PmOnrKz454DiVIwe0S4uFOxIQtBVgebqVmcONLGzYgdxkyTlyXzmaHkeBJovX++q/MiEGVNcM4sZTbCJ+bSrHZ3a/SJ4RQx/caxE6iCBCKIXXdm1E9XN1pP4/4bzEDikp72gI5HOZ33yXR63QB3IUlYq3Joz7++My+zECXF8L2JNnEXdlMqvn3L1qBMeFkS422G6EFiK7VX8w2/16RcMG1rqs4vcUaFn0w8H8t9NAZYjRQmPQZgah/PijIPfD1re3hL0ZyDO7zJoUvZoAhN6fY5aaa0/w6/KoEnFMNiv0tJPECyuI0L9TjF7GqBQFzo/LhAdE7cx/WnUvB6e0GXEnZKzXzLqh6U2GZz57x87K2tq98Ya88mfn8FB+rdBPbQvafsJxaGHojMf7w3wAxnLBC+r+neZo8JmdGhz8Hp0YKwayXH/rOCvzm+OtF+/uwXR5tHMI 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: Lorenzo Stoakes Signed-off-by: Nico Pache --- mm/khugepaged.c | 128 ++++++++++++++++++++++++++---------------------- 1 file changed, 69 insertions(+), 59 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 64086488ca01..0058970d4579 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2417,6 +2417,70 @@ 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, + unsigned int *cur_progress, struct collapse_control *cc) +{ + struct mm_struct *mm = vma->vm_mm; + bool triggered_wb = false; + enum scan_result result; + struct file *file; + pgoff_t pgoff; + + if (vma_is_anonymous(vma)) { + result = collapse_scan_pmd(mm, vma, addr, mmap_locked, cur_progress, cc); + goto end; + } + + file = get_file(vma->vm_file); + pgoff = linear_page_index(vma, addr); + + mmap_read_unlock(mm); + *mmap_locked = false; +retry: + result = collapse_scan_file(mm, addr, file, pgoff, cur_progress, cc); + + /* + * For MADV_COLLAPSE, when encountering dirty pages, try to writeback, + * then retry the collapse one time. + */ + if (!cc->is_khugepaged && result == SCAN_PAGE_DIRTY_OR_WRITEBACK && + triggered_wb && mapping_can_writeback(file->f_mapping)) { + const loff_t lstart = (loff_t)pgoff << PAGE_SHIFT; + const loff_t lend = lstart + HPAGE_PMD_SIZE - 1; + + filemap_write_and_wait_range(file->f_mapping, lstart, lend); + triggered_wb = true; + goto retry; + } + 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) @@ -2489,36 +2553,9 @@ 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, - &cur_progress, 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, - &cur_progress, cc); - } - - if (*result == SCAN_SUCCEED) - ++khugepaged_pages_collapsed; + *result = collapse_single_pmd(khugepaged_scan.address, + vma, &mmap_locked, &cur_progress, cc); /* move to next address */ khugepaged_scan.address += HPAGE_PMD_SIZE; progress += cur_progress; @@ -2819,13 +2856,12 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, 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; 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: -- 2.53.0