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To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, chrisl@kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Stat-Signature: 6qkmq9t89c97t1mmsn637r1y7ucqy3om X-Rspam-User: X-Rspamd-Queue-Id: 8577EC0002 X-HE-Tag: 1767008267-976420 X-HE-Meta: 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 +lqZ/YYo 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Dec 29, 2025 at 6:07=E2=80=AFAM Barry Song <21cnbao@gmail.com> wrot= e: > > On Mon, Dec 29, 2025 at 10:37=E2=80=AFAM Andrew Morton wrote: > > > > On Sat, 27 Dec 2025 17:58:40 +0800 wale zhang wrote: > > > > > > No. You still don=E2=80=99t understand my point. The BUILD_BUG mean= s this > > > > code will never have a chance to be compiled under any possible > > > > kernel configuration. That makes it dead code. If there is any > > > > kernel .config in which it can be built, then we should fix it. > > > > > > > > This set_pmd_migration_entry() has no chance of ever being built. > > > > > > Hello Barry, > > > > > > > Please share the .config which was used to trigger this build error. > > > > (It is strange to have this should-never-be-compiled code. Why not jus= t > > delete it and let the compiler/linker report the error.) > > Right. We should entirely drop it in mainline. If Wale does want an > O0 build, then the only call to set_pmd_migration_entry() that is not > under > > #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > > is migrate_vma_collect_huge_pmd() in mm/migrate_device.c. > > Then what we really need is as follows: > > diff --git a/include/linux/swapops.h b/include/linux/swapops.h > index 8cfc966eae48..fdd4375d5d90 100644 > --- a/include/linux/swapops.h > +++ b/include/linux/swapops.h > @@ -339,17 +339,6 @@ static inline pmd_t swp_entry_to_pmd(swp_entry_t ent= ry) > } > > #else /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ > -static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *p= vmw, > - struct page *page) > -{ > - BUILD_BUG(); > -} > - > -static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvm= w, > - struct page *new) > -{ > - BUILD_BUG(); > -} > > static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *= p) { } > > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 23379663b1e1..74d23c91626a 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -195,8 +195,9 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, = unsigned long start, > return migrate_vma_collect_skip(start, end, walk); > } > > - if (thp_migration_supported() && > - (migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) && > + > +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > + if ((migrate->flags & MIGRATE_VMA_SELECT_COMPOUND) && > (IS_ALIGNED(start, HPAGE_PMD_SIZE) && > IS_ALIGNED(end, HPAGE_PMD_SIZE))) { > > @@ -226,6 +227,7 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, = unsigned long start, > spin_unlock(ptl); > return 0; > } > +#endif > > fallback: > spin_unlock(ptl); > > Thanks > Barry > OK. I will prepare the next patch to delete this unnecessary codes. Thank you for your guidance. -- Thanks Wale