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b=KQ+donDYQjFaHp/brCTIbu5qdbGMTuVQVgQn6HRb161dCXNKXrZxG7F6TENzoHDgJ +8WRpKalgfXf6mUngv7VtJYq8L7BtBsem87Zryd1Y6L0MdQQb8m72c5q9Rltqis3jZ OGJclJUd9bV98pA7dcXZmlErgT2iAOZmY4Oex+gCPIyLoLvN4gK7aYoIlw7N5/2xkb iQc24Wd06mPXtaRk06wFpZYTpktook79dfF1rMNlyechAt5tewM5SWCurvm/9KKyMZ 3K6noyAlqqDM8irucQwQdxUGoYApxwFvXi4wP2kyolJEyRvxKhM7UPOM4zidRdZojc XykzldYoWkCgw== Message-ID: <4bfec2c1-9747-49d2-a490-87ab204cec1c@kernel.org> Date: Thu, 12 Mar 2026 10:44:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v4 2/6] mm/migrate: skip data copy for already-copied folios To: Shivank Garg , akpm@linux-foundation.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@kernel.org, willy@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, dave@stgolabs.net, Jonathan.Cameron@huawei.com, rkodsara@amd.com, vkoul@kernel.org, bharata@amd.com, sj@kernel.org, weixugc@google.com, dan.j.williams@intel.com, rientjes@google.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, dave.hansen@intel.com, hannes@cmpxchg.org, jhubbard@nvidia.com, peterx@redhat.com, riel@surriel.com, shakeel.butt@linux.dev, stalexan@redhat.com, tj@kernel.org, nifan.cxl@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260309120725.308854-3-shivankg@amd.com> <20260309120725.308854-8-shivankg@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: CF35520003 X-Rspamd-Server: rspam08 X-Stat-Signature: 5njsoccdcx5ay6o46y9j9rys8nmbk1b7 X-HE-Tag: 1773308667-382990 X-HE-Meta: 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 4eHFfBAT WaIrLAYzIFedQ1jJCw8EBDTZtAZW2cS9KQi7i4e68J6AGf7DGEujxPuGZ9Hz1JYp+EmOuH4bwy/sJ1WboWcbg+nih1ACw4NVmmEf9gW9KDEDvzADInmRDls2NBzJDlN6O2mmBjSw1/2j7vGLDgKns6ciyGg9B35V2FIW//W/ebuRff04zkYJquQH9tVEGcPrvFqvy2cSxjYwwQoX3SFVStpAulREt1Rdal+fcIi4oJUtX9GgD988HoYW4S7YLu20Da/vqAVYmkixMHza0Sa6Hcg7iF9WV0xgwttlwOEZcyZYZSkjiqKHrQkbroM60TNKzdQgBBXpxktuDvEDHiu7Js9sCwuXcux78oZT5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/9/26 13:07, Shivank Garg wrote: > Add a PAGE_ALREADY_COPIED flag to the dst->private migration state. > When set, __migrate_folio() skips folio_mc_copy() and performs > metadata-only migration. All callers currently pass > already_copied=false. The batch-copy path enables it in a later patch. > > Move the dst->private state enum earlier in the file so > __migrate_folio() and move_to_new_folio() can see PAGE_ALREADY_COPIED. > > Signed-off-by: Shivank Garg > --- > mm/migrate.c | 52 +++++++++++++++++++++++++++++++--------------------- > 1 file changed, 31 insertions(+), 21 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 1bf2cf8c44dd..1d8c1fb627c9 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -848,6 +848,18 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio) > } > EXPORT_SYMBOL(folio_migrate_flags); > > +/* > + * To record some information during migration, we use unused private > + * field of struct folio of the newly allocated destination folio. > + * This is safe because nobody is using it except us. > + */ > +enum { > + PAGE_WAS_MAPPED = BIT(0), > + PAGE_WAS_MLOCKED = BIT(1), > + PAGE_ALREADY_COPIED = BIT(2), > + PAGE_OLD_STATES = PAGE_WAS_MAPPED | PAGE_WAS_MLOCKED | PAGE_ALREADY_COPIED, All these states really only apply to proper folios (not movable_ops). So once we complete decoupling movable_ops migration from folio migration, these flags would only appear in the folio migration part. Can we convert them first to state it clearly already that these are folio migration flags? FOLIO_MF_WAS_MAPPED ... -- Cheers, David