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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2026-08-12 at 15:23 +0200, David Hildenbrand (Arm) wrote: > On 8/12/26 15:02, Rik van Riel wrote: > > On Wed, 2026-08-12 at 13:50 +0200, David Hildenbrand (Arm) wrote: > > > On 8/11/26 04:51, Rik van Riel wrote: > > > >=20 > > > > +/* > > > > + * The caller has already run every per-PTE safety check > > > > (present, > > > > + * write-fault, gup_must_unshare()) on the PTE, so this only > > > > does > > > > the > > > > + * per-folio work: the refcount grab, the FOLL_PIN > > > > accessibility > > > > fault-in, > > > > + * dirty/accessed marking, and the array fill with the cache > > > > flush. > > > > + */ > > >=20 > > > If a function needs 4 lines of internal doc to understand what it > > > does, then > > > maybe it's not the right function name or abstraction. :) > > >=20 > > > I don't particularly enjoy the "commit" terminology, it looses > > > the > > > detail of the > > > most important thing this function is supposed to to: grab a > > > folio > > > reference. > > >=20 > >=20 > > Should we rename it to gup_grab_folio() ? >=20 > It does more than grabbing, hm, let me think. >=20 > gup_grab_and_store_folio_pages() >=20 > not sure. It does more than grabbing, but if we want to have the PUD path use this same function, we will probably want to move the gup_fill_pages() call to outside the lock. At that point we'll be left with grabbing the pages, and marking the folio dirty/accessed, plus the arch_make_folio_accessible() call, which seems to be a noop on anything but s390, where it makes the page accessible to the hypervisor (not sure when/why GUP needs this). >=20 > >=20 > > Looking at the differences between the pte and pmd > > code, there is another big thing that stands out. > >=20 > > The pte code will call mark_folio_dirty() when > > needed, but the pmd and pud code do not. >=20 > Yes, and my gut feeling is that the same helper should be also used > in the other > places. Maybe there is no real bug there, but the inconsistency is > concerning. The page table dirty bits should ensure that we don't lose any data written to the page, but not marking the folio dirty might mess with dirty balancing. --=20 All Rights Reversed.