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b=qvywMMVpC4SHksnMSWVf9rIP6EZzyn0U4GekTolsw7Odp6XQAIfTHspEcfP6447IspUfEh6HHf2bpiPQCeNKduJPvh+R0M6GtOf7ZfyzJTAZ6HOHVpEtPY/KD90o5ZFDDiuZJ5I1yCZZz9b8jWs7+h1vqdXE7DOpKEQGT/0QGos= 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 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 X-Stat-Signature: zf3jk4mswj3duh6ce8z7ej8gd73rsai9 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1E397100002 X-HE-Tag: 1772097840-996335 X-HE-Meta: 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 OAL6x5qP zD4cfQ90VFms2xs9cQgr2B3Ff7WMHFJTDXOWz0o3wipy02BI7pJb9NL1BsArID57StQaurxZDbNi3tmWHj5iEQZbGLBXy2zV10LEhASNxC9nrSM1fGTy66SmF3O0F3s8AqqyUYTMZSDuc1CH8IZCC+uTB34Rl1wIt3MXDHorx7GitALoA2ZZmRHbIv4Y1pNkmbQ9JkdxeMGtrEk/zFbCkFzLxffzrT/YZiphyXfXGP3CZ+vrG6IRqAFl5GqCFakULirR734ytbr2KIS2K6U/wa3mRN88pSXQEHNUajYx1pKIthqwoa5Jtt/FoNACZwhj335Z9UFt/LoyddVTVedhTy8DKRgWDsZPngMop9KJScoZFEgUcTErSwJqVbDU1XQQFD+Atw4zwYtUGX/61L2oqQpJyvpKEuc+Wy5dDYA48q51fuqe+EvF3bXhpRvDki0pmy4ASXcIrt2cjllmosEdDVHOlWyPyA/3vtxK5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: