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Howlett" , "Lorenzo Stoakes (Oracle)" , "Matthew Wilcox (Oracle)" , Michal Hocko , Mike Rapoport , Muchun Song , Nikita Kalyazin , Oscar Salvador , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 09/15] userfaultfd: introduce vm_uffd_ops->alloc_folio() Date: Thu, 2 Apr 2026 07:11:50 +0300 Message-ID: <20260402041156.1377214-10-rppt@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260402041156.1377214-1-rppt@kernel.org> References: <20260402041156.1377214-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B877D100005 X-Stat-Signature: 4fef7d7zourbnkh466tynem33kkn9w6b X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1775103188-129844 X-HE-Meta: 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 Kp848jxl Rnr0iWF5mBMSxBzqLbaIFyI8TwqlBd8H7LoLzjRI+koKgYTGRE8Ih0eNSmzv/puJAt0aXiHL+b/N/5PoJh/9ZbLHz1psQrT0xXwwf/uEIFH8Mc5ne6HL1zZefSYLdpZUz2GCmEFjGzfa9Zby6M9/0W/sDXiLmBT7O4LYsw5TkGyYbnMa6xV797dg3q3gC/LFcuHtIdwuv6hYP8H794AkEkcDbXqHAot+dm9MG1cDAUXl1JxfOWqZUmRHRg5IYD2+goObVlTfe0/9dTVx42W62M9io+60+YN7o3e9OkZqg6CA5s1BSCc4YxZ2ODw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" and use it to refactor mfill_atomic_pte_zeroed_folio() and mfill_atomic_pte_copy(). mfill_atomic_pte_zeroed_folio() and mfill_atomic_pte_copy() perform almost identical actions: * allocate a folio * update folio contents (either copy from userspace of fill with zeros) * update page tables with the new folio Split a __mfill_atomic_pte() helper that handles both cases and uses newly introduced vm_uffd_ops->alloc_folio() to allocate the folio. Pass the ops structure from the callers to __mfill_atomic_pte() to later allow using anon_uffd_ops for MAP_PRIVATE mappings of file-backed VMAs. Note, that the new ops method is called alloc_folio() rather than folio_alloc() to avoid clash with alloc_tag macro folio_alloc(). Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: James Houghton --- include/linux/userfaultfd_k.h | 6 +++ mm/userfaultfd.c | 92 ++++++++++++++++++----------------- 2 files changed, 54 insertions(+), 44 deletions(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 66dfc3c164e6..55a67421de0a 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -91,6 +91,12 @@ struct vm_uffd_ops { * The returned folio is locked and with reference held. */ struct folio *(*get_folio_noalloc)(struct inode *inode, pgoff_t pgoff); + /* + * Called during resolution of UFFDIO_COPY request. + * Should allocate and return a folio or NULL if allocation fails. + */ + struct folio *(*alloc_folio)(struct vm_area_struct *vma, + unsigned long addr); }; /* A combined operation mode + behavior flags. */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 832dbdde5868..771a1e607c4c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -42,8 +42,26 @@ static bool anon_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags) return true; } +static struct folio *anon_alloc_folio(struct vm_area_struct *vma, + unsigned long addr) +{ + struct folio *folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, + addr); + + if (!folio) + return NULL; + + if (mem_cgroup_charge(folio, vma->vm_mm, GFP_KERNEL)) { + folio_put(folio); + return NULL; + } + + return folio; +} + static const struct vm_uffd_ops anon_uffd_ops = { .can_userfault = anon_can_userfault, + .alloc_folio = anon_alloc_folio, }; static const struct vm_uffd_ops *vma_uffd_ops(struct vm_area_struct *vma) @@ -456,7 +474,8 @@ static int mfill_copy_folio_retry(struct mfill_state *state, struct folio *folio return 0; } -static int mfill_atomic_pte_copy(struct mfill_state *state) +static int __mfill_atomic_pte(struct mfill_state *state, + const struct vm_uffd_ops *ops) { unsigned long dst_addr = state->dst_addr; unsigned long src_addr = state->src_addr; @@ -464,16 +483,12 @@ static int mfill_atomic_pte_copy(struct mfill_state *state) struct folio *folio; int ret; - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, state->vma, dst_addr); + folio = ops->alloc_folio(state->vma, state->dst_addr); if (!folio) return -ENOMEM; - ret = -ENOMEM; - if (mem_cgroup_charge(folio, state->vma->vm_mm, GFP_KERNEL)) - goto out_release; - - ret = mfill_copy_folio_locked(folio, src_addr); - if (unlikely(ret)) { + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) { + ret = mfill_copy_folio_locked(folio, src_addr); /* * Fallback to copy_from_user outside mmap_lock. * If retry is successful, mfill_copy_folio_locked() returns @@ -481,9 +496,15 @@ static int mfill_atomic_pte_copy(struct mfill_state *state) * If there was an error, we must mfill_put_vma() anyway and it * will take care of unlocking if needed. */ - ret = mfill_copy_folio_retry(state, folio); - if (ret) - goto out_release; + if (unlikely(ret)) { + ret = mfill_copy_folio_retry(state, folio); + if (ret) + goto err_folio_put; + } + } else if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { + clear_user_highpage(&folio->page, state->dst_addr); + } else { + VM_WARN_ONCE(1, "Unknown UFFDIO operation, flags: %x", flags); } /* @@ -496,47 +517,30 @@ static int mfill_atomic_pte_copy(struct mfill_state *state) ret = mfill_atomic_install_pte(state->pmd, state->vma, dst_addr, &folio->page, true, flags); if (ret) - goto out_release; -out: - return ret; -out_release: + goto err_folio_put; + + return 0; + +err_folio_put: + folio_put(folio); /* Don't return -ENOENT so that our caller won't retry */ if (ret == -ENOENT) ret = -EFAULT; - folio_put(folio); - goto out; + return ret; } -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) @@ -549,7 +553,7 @@ 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); _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), dst_vma->vm_page_prot)); -- 2.53.0