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To: Andrew Morton Cc: Barry Song <21cnbao@gmail.com>, "David Hildenbrand (Red Hat)" , chrisl@kernel.org, ziy@nvidia.com, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 29416C0002 X-Stat-Signature: yoptaq6tjo7dyh4m4g3duyithhdziksf X-Rspam-User: X-HE-Tag: 1767173458-697300 X-HE-Meta: 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 VvcFHkY9 GEDBnOCq5GDEym6vZU4YbCT55LhEYUqGXAvLOdDLC39QEA3kRTjHIwIIr7ymsnPYXlpWyxK6enm25ZEfSuJx4HhBmFkh/oh8mnJQZOzNvLEbRZTWGGxUkXEcFll7sc4r/SoSXhn4Dyz4RZnZHqR5F9D2exnPsKhzx2brq044UxDvl6ALPveYrQ6D/O/1XY1ObeUhb8MBX5/C00f/vsr27HQCJG9uH7KYrxs5zHomQPDzVtlJ9C+ySgVy7XK/kOEhi8nmyjj018Q9LsuwwhSD8bHlzKr/OXTU5Rf7hnziC85q1OglOblgVoXvgNqeydFaHKIQs+qaIzs9EFLgTexe/GoTcjY0huqsUqK11FbOkR1Tx7OfZCdeRjOTxsY+xe2lcVZlOpoCydTQ1vx3JBJj5hOzmxKlhzrczgi/yTZBpH78YORTFR3SvbigHgnkkRhDpqpAlrd7onrP60wrm2RfAE3612ObViOfasqqKUMHhsdKktyQ= 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 Wed, Dec 31, 2025 at 5:35=E2=80=AFAM Andrew Morton wrote: > > On Wed, 31 Dec 2025 10:28:25 +1300 Barry Song <21cnbao@gmail.com> wrote: > > > On Wed, Dec 31, 2025 at 8:50=E2=80=AFAM David Hildenbrand (Red Hat) > > wrote: > > > > > > > > > > - break; > > > > +#ifdef CONFIG_NO_PAGE_MAPCOUNT > > > > + last =3D atomic_add_negative(-1, &folio->_entire_mapc= ount); > > > > + if (level =3D=3D PGTABLE_LEVEL_PMD && last) > > > > + nr_pmdmapped =3D folio_large_nr_pages(folio); > > > > + nr =3D folio_dec_return_large_mapcount(folio, vma); > > > > + if (!nr) { > > > > + /* Now completely unmapped. */ > > > > + nr =3D folio_large_nr_pages(folio); > > > > + } else { > > > > + partially_mapped =3D last && > > > > + nr < folio_large_nr_pages(folio); > > > > + nr =3D 0; > > > > > > The whole code was written to avoid ifdefs. > > > > The #ifdefs are only for -O0 builds, which are never a > > mainline requirement. However, dropping functions that > > contain nothing but a BUILD_BUG() seems reasonable? > > Let's not make -O0 an objective, please. We often make assumptions > about dead code elimination in order to keep kernel code more pleasing > to read and to maintain. Let me think if there is any other way to achieve it. > > If those functions were actually required, the compiler > > would fail anyway. In that case, there doesn=E2=80=99t seem to be > > much value in keeping wrapper functions whose sole purpose > > is to contain a single BUILD_BUG(). > > I agree with that part of the patch - if the thing only does a > BUILD_BUG() then let's simply remove it. If somehow the compiler tries > to reference the now-not-present function then we'll get an error message > anyway. > Thanks Wale