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b=utqP9oHbhs5h0axqgKUQ8EVhZspF/01+L8RMIchQwEJbwSxodZ2XK5RNV+Ulp3R/+ rWHvMGEpLW5I+uFjgj1PdJcktrR3LuNNO44t5jYTJ9D8Qi3hXwmHdkjbrco02TYY9B 4U2BWbL/RJKE6dGSDzyeLRl4MuMQkrrgXIFyPQiaPeSWD9NO8f0MW5V6mnlIChyrvv 06LXFI/j51NrNvMyWd9ZK3Ky14ZSKKnLCQd+APmh8zxV7K3LzO9R/zahIk2494fb7C eLVfAtc54SEEIfR/+UCPZZF2WB+TPin5jA3RUxdYU1FaUZ/InK+Sda0NOzIGkksvzJ b9XKaDeGVNIvQ== Message-ID: <56e07b6a-dd33-46eb-9faf-0310169e22cc@kernel.org> Date: Thu, 12 Mar 2026 10:27:47 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v3 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, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, 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: <20260311211315.450947-1-npache@redhat.com> <20260311211315.450947-6-npache@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260311211315.450947-6-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9E0F9140005 X-Stat-Signature: bw8jycg9ct31q8ghn4x1a7e6xjx5wbt9 X-Rspam-User: X-HE-Tag: 1773307682-165211 X-HE-Meta: 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 ARnFp6xc tKEK3Xb9pH3x5LjTwS51A4Tf1uysI4Wer5O66co+1zuaXZ0Uj0zIwtwl6wvb5t8owC9uf2hUyErema6y66abm1d3IYot2QIjur5dla8tTUztOCWtchpwij5+0KWMkPueERwZZrWkBCoMci8vGCermEi92cOlR2lzXe2eiQZcdKZJZ/56zU/Avd98dvTxj4oxmhuoZBiWG3Aokzm0IpTXPuh/nSP7iBMZWLHk5/xr7qdynt0gtqiEmKK+wCrneJwgT+dQw9T1qwWbXrxxP0HKllvjLUMAUrdxD60B2xE58c677B/0jqwSC3dZqt/lmQevorEberfqgJRGR0FEMvSqIdbmzXEstGm/+sIwOv/E91bdd2uukDFO2hhnv6miciER9OT8DqWWCdDlanYNxg4UQ5BS92RzO+wKS14BXwSfjfk9+rGk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/11/26 22:13, 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. > > By moving the madvise_collapse writeback-retry logic into the helper > function we can also avoid having to revalidate the VMA. > > We also guard the khugepaged_pages_collapsed variable to ensure its only > incremented for khugepaged. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 120 +++++++++++++++++++++++++----------------------- > 1 file changed, 63 insertions(+), 57 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 33ae56e313ed..733c4a42c2ce 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2409,6 +2409,65 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, > 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; > + 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, 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, 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) { > + mmap_read_lock(mm); > + if (collapse_test_exit_or_disable(mm)) > + result = SCAN_ANY_PROCESS; > + else > + result = try_collapse_pte_mapped_thp(mm, addr, > + !cc->is_khugepaged); > + if (result == SCAN_PMD_MAPPED) > + result = SCAN_SUCCEED; > + mmap_read_unlock(mm); > + } > +end: > + if (cc->is_khugepaged && result == SCAN_SUCCEED) > + ++khugepaged_pages_collapsed; > + return result; > +} > + > static void collapse_scan_mm_slot(unsigned int progress_max, > enum scan_result *result, struct collapse_control *cc) > __releases(&khugepaged_mm_lock) > @@ -2479,34 +2538,9 @@ static void collapse_scan_mm_slot(unsigned int progress_max, > 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; > if (!mmap_locked) > @@ -2806,9 +2840,7 @@ 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); > @@ -2823,46 +2855,20 @@ 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; Okay, we can get rid of this because collapse_single_pmd() will never drop the lock, to retake it, returning with "mmap_locked == true". If it dropped the lock, even if it relocked, it will always return with the lock dropped and "mmap_locked == false". The "if (!mmap_locked)" will properly set "*lock_dropped = true;". Acked-by: David Hildenbrand (Arm) -- Cheers, David