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b=j8WNbSnNmvDwOEQchSrC+awLU1F9TWqkmTuQb3KvRpAWzLZUou3D2zzmuiS70gZst Bwh7Rl9TvfXwyWnldJX5HHuaemXXQi7DRfRcLyJPjVFKnw1+1TlSa2TwmtDO4gC3qZ SsjHQhoYF375E35KJUUMbA3z9iVJvPN1gmhF5c+qtjvl8fDY/ZAsG4pCvqkzZOlwrZ 96lpeY6THs1o2800tnctleliaxJ6DVjEL58BBvLikn6o6CIi0KBcSywr5bhQOmeG6k fANs39ciRtTxyGcNUR7fDgCyNsxmJGtaT5oJWRjq5/I1L9qFqOKV9/oNAUWE9k2uGs OxrKcLaTxIjkg== Message-ID: <546df3d8-2f63-4a83-be44-4cfe21ddb4c6@kernel.org> Date: Fri, 6 Mar 2026 16:59:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 06/13] mm: Add helpers to create migration entries from struct pages To: Jordan Niethe , linux-mm@kvack.org Cc: balbirs@nvidia.com, matthew.brost@intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, ziy@nvidia.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, lyude@redhat.com, dakr@kernel.org, airlied@gmail.com, simona@ffwll.ch, rcampbell@nvidia.com, mpenttil@redhat.com, jgg@nvidia.com, willy@infradead.org, linuxppc-dev@lists.ozlabs.org, intel-xe@lists.freedesktop.org, jgg@ziepe.ca, Felix.Kuehling@amd.com, jhubbard@nvidia.com, maddy@linux.ibm.com, mpe@ellerman.id.au, ying.huang@linux.alibaba.com References: <20260202113642.59295-1-jniethe@nvidia.com> <20260202113642.59295-7-jniethe@nvidia.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: <20260202113642.59295-7-jniethe@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 80A9616001B X-Rspamd-Server: rspam07 X-Stat-Signature: uor77karqu6xi76a6rkrycxegep3w9zp X-Rspam-User: X-HE-Tag: 1772812808-710589 X-HE-Meta: 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 eQDqMcO/ ytDWkLl7qEZVa953KRQAadTlxNdJsXQK7t1tGGCcdyXKVJadVh7jFT6IIa2y846JGLyRKORCEEdpCR5Z7mOQwzX2Y7OoLkeYj3+6LffV9Uh06yay5wbvdbKGyaT0HeNWC+KOohiebMlYTyjQdf5Wnh0p2zAACL/A5nsKrohB077XpcObtlC1HDO5wv7bXWKqc0nKZbrEiOl/t7jpenRrQfRbqArrhTEmBm3DVCRV09J1R2TmvHyHhuqmdsvzlbMgGZDYXg/y161vjZxz/JPzaDLEmaQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/2/26 12:36, Jordan Niethe wrote: > To create a new migration entry for a given struct page, that page is > first converted to its pfn, before passing the pfn to > make_readable_migration_entry() (and friends). > > A future change will remove device private pages from the physical > address space. This will mean that device private pages no longer have a > pfn and must be handled separately. > > Prepare for this with a new set of helpers: > > - make_readable_migration_entry_from_page() > - make_readable_exclusive_migration_entry_from_page() > - make_writable_migration_entry_from_page() This is pretty horrible. And everything I see in successive patches around that is not any better. Seriously, look at how terrible make_readable_exclusive_migration_entry_from_page() is. make_readable_exclusive_migration_device_private_entry is not any better, but at least doesn't have this questionable flags parameter. Correct me if I am wrong: all we want is: make_readable_migration_entry() etc. to create something that softleaf_to_page() / softleaf_to_folio() can properly convert to a folio, right? So maybe we should convert make_readable_migration_entry() and friends to consume a page (not add new functions ...), and let it internally figure out how to communicate in the entry that what we are dealing with is not an ordinary pfn, but a special device-private entry. > > Signed-off-by: Jordan Niethe > --- > v1: > - New to series > v2: > - Add flags param > v3: > - No change > v4: > - s/make_writeable_migration_entry_from_page/make_writable_migration_entry_from_page/ > for the !CONFIG_MIGRATION case > --- > include/linux/leafops.h | 14 ++++++++++++++ > include/linux/swapops.h | 34 ++++++++++++++++++++++++++++++++++ > mm/huge_memory.c | 29 +++++++++++++++++------------ > mm/hugetlb.c | 15 +++++++++------ > mm/memory.c | 5 +++-- > mm/migrate_device.c | 12 ++++++------ > mm/mprotect.c | 10 +++++++--- > mm/rmap.c | 12 ++++++------ > 8 files changed, 96 insertions(+), 35 deletions(-) > > diff --git a/include/linux/leafops.h b/include/linux/leafops.h > index a9ff94b744f2..52a1af3eb954 100644 > --- a/include/linux/leafops.h > +++ b/include/linux/leafops.h > @@ -363,6 +363,20 @@ static inline unsigned long softleaf_to_pfn(softleaf_t entry) > return swp_offset(entry) & SWP_PFN_MASK; > } > > +/** > + * softleaf_to_flags() - Obtain flags encoded within leaf entry. > + * @entry: Leaf entry, softleaf_has_pfn(@entry) must return true. > + * > + * Returns: The flags associated with the leaf entry. > + */ > +static inline unsigned long softleaf_to_flags(softleaf_t entry) > +{ > + VM_WARN_ON_ONCE(!softleaf_has_pfn(entry)); > + > + /* Temporary until swp_entry_t eliminated. */ > + return swp_offset(entry) & (SWP_MIG_YOUNG | SWP_MIG_DIRTY); > +} The whole flags stuff does not really belong in this patch. If there are cleanups to be had, perform them separately, please. -- Cheers, David