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See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 5D922140004 X-Rspam-User: X-Stat-Signature: z6hz3chyne7fi5y67cd6ffdo9ujat8y4 X-Rspamd-Server: rspam09 X-HE-Tag: 1781091264-209222 X-HE-Meta: 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 Q/5NTqTj 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jun 10, 2026 at 11:54:01AM +0200, David Hildenbrand (Arm) wrote: > > Yes. iov_iter_extract_bvecs and thus the block direct I/O fast path > > would instantly benefit from that. > The tricky bit for such an interface is that, soon, some pages won't be folios, > but we could still end up with non-folio pages in the address space (e.g., > vm_insert_page()) and have to pin+return them. So using folios is not future-proof. I'm still doubtful on the "soon" beause of all the issues like this in the I/O path. > There are some long-term plans on providing an interface that would abstract how > you refcount something you GUP'ed. (because, some pages we GUP in the future > might not even have a dedicated refcount, all still fairly unclear). But it's > all not really finalized I think. > > For now, we could expose a folio+page/offset+nr_pages interface, where we, > long-term, would not be able to return non-folio pages (e.g., vm_insert_page()) > and would instead, in the future, fail the request if we stumble over a > non-folio thing in the page tables. That sounds reasonable for now. I think whatever we're going to use for direct I/O has to also support non-folio pages, especially PCI P2P memory. So coming up with an interface that support this ASAP would be helpful. > Another solution would be, exposing page-ranges (e.g., page + nr_pages), whereby > we'd say, that all pages in a range belong to the same compound page, and that > we took a single reference for all pages in the range. IOW, page_folio() would > for now be the same for all pages in a range. This does sound like a reasonable short-term improvement. One annoying issue with returning only order 0 page in the current interfaces is that it fills up the pages array in the caller for no good reason.