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[174.91.117.149]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8971cd8aff6sm21074646d6.27.2026.02.11.11.37.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Feb 2026 11:37:28 -0800 (PST) Date: Wed, 11 Feb 2026 14:37:26 -0500 From: Peter Xu To: Mike Rapoport Cc: linux-mm@kvack.org, Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Muchun Song , Nikita Kalyazin , Oscar Salvador , Paolo Bonzini , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH RFC 09/17] userfaultfd: introduce vm_uffd_ops->alloc_folio() Message-ID: References: <20260127192936.1250096-1-rppt@kernel.org> <20260127192936.1250096-10-rppt@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Sun, Feb 08, 2026 at 12:22:52PM +0200, Mike Rapoport wrote: > On Mon, Feb 02, 2026 at 05:13:20PM -0500, Peter Xu wrote: > > On Tue, Jan 27, 2026 at 09:29:28PM +0200, Mike Rapoport wrote: > > > > [...] > > > > > -static int mfill_atomic_pte_zeroed_folio(pmd_t *dst_pmd, > > > - struct vm_area_struct *dst_vma, > > > - unsigned long dst_addr) > > > +static int mfill_atomic_pte_copy(struct mfill_state *state) > > > { > > > - struct folio *folio; > > > - int ret = -ENOMEM; > > > - > > > - folio = vma_alloc_zeroed_movable_folio(dst_vma, dst_addr); > > > - if (!folio) > > > - return ret; > > > - > > > - if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL)) > > > - goto out_put; > > > + const struct vm_uffd_ops *ops = vma_uffd_ops(state->vma); > > > > > > - /* > > > - * The memory barrier inside __folio_mark_uptodate makes sure that > > > - * zeroing out the folio become visible before mapping the page > > > - * using set_pte_at(). See do_anonymous_page(). > > > - */ > > > - __folio_mark_uptodate(folio); > > > + return __mfill_atomic_pte(state, ops); > > > +} > > > > > > - ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, > > > - &folio->page, true, 0); > > > - if (ret) > > > - goto out_put; > > > +static int mfill_atomic_pte_zeroed_folio(struct mfill_state *state) > > > +{ > > > + const struct vm_uffd_ops *ops = vma_uffd_ops(state->vma); > > > > > > - return 0; > > > -out_put: > > > - folio_put(folio); > > > - return ret; > > > + return __mfill_atomic_pte(state, ops); > > > } > > > > > > static int mfill_atomic_pte_zeropage(struct mfill_state *state) > > > @@ -542,7 +546,7 @@ static int mfill_atomic_pte_zeropage(struct mfill_state *state) > > > int ret; > > > > > > if (mm_forbids_zeropage(dst_vma->vm_mm)) > > > - return mfill_atomic_pte_zeroed_folio(dst_pmd, dst_vma, dst_addr); > > > + return mfill_atomic_pte_zeroed_folio(state); > > > > After this patch, mfill_atomic_pte_zeroed_folio() should be 100% the same > > impl with mfill_atomic_pte_copy(), so IIUC we can drop it. > > It will be slightly different after the next patch to emphasize that > copying into MAP_PRIVATE actually creates anonymous memory. True. It might be helpful to leave a line in the commit message so it's intentional to temporarily have two functions do the same thing, but I'm OK either way. Thanks, -- Peter Xu