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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, "Harry Yoo (Oracle)" Subject: [PATCH v4 03/15] userfaultfd: introduce mfill_establish_pmd() helper Date: Thu, 2 Apr 2026 07:11:44 +0300 Message-ID: <20260402041156.1377214-4-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-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5F40840006 X-Stat-Signature: 9eotukq1mpxg6pkjm5d1zjdctoh6qjm1 X-HE-Tag: 1775103148-790783 X-HE-Meta: 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 k/WaUaLb 1VPw7DPci/AC+OvnewpwpBI+fWrDobvFwZbkOwA5n17ifPDhRqZO1HMo6cZXWexlZz1HYVtn2RWR711GFnzOq5qDy29ET2nP98+bWOuZudSzM1ePMXms9yh3fb4z/FafnElOa/Q+9MkkItnUarXKvrc0AIBAXna3U2DxiWNvZjZtM5gkQ97U4h//D8mVBm0SXTKGLm30xTS2NNYnr8OFlbGx3kGWDGsHCAEVhzwBP+nqS1RYg/GcHZDcz+r9eKf7KUbHTYoXDakuO+4FHj98SPv9LXasNsRiyl4/uXvuUT9Sb3cLy7joKaDdj7mQ3x31GUTqX Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" There is a lengthy code chunk in mfill_atomic() that establishes the PMD for UFFDIO operations. This code may be called twice: first time when the copy is performed with VMA/mm locks held and the other time after the copy is retried with locks dropped. Move the code that establishes a PMD into a helper function so it can be reused later during refactoring of mfill_atomic_pte_copy(). Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Harry Yoo (Oracle) --- mm/userfaultfd.c | 102 ++++++++++++++++++++++++----------------------- 1 file changed, 52 insertions(+), 50 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index c4074b6f4aca..f653fb3f74df 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -157,6 +157,56 @@ static void uffd_mfill_unlock(struct vm_area_struct *vma) } #endif +static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + + pgd = pgd_offset(mm, address); + p4d = p4d_alloc(mm, pgd, address); + if (!p4d) + return NULL; + pud = pud_alloc(mm, p4d, address); + if (!pud) + return NULL; + /* + * Note that we didn't run this because the pmd was + * missing, the *pmd may be already established and in + * turn it may also be a trans_huge_pmd. + */ + return pmd_alloc(mm, pud, address); +} + +static int mfill_establish_pmd(struct mfill_state *state) +{ + struct mm_struct *dst_mm = state->ctx->mm; + pmd_t *dst_pmd, dst_pmdval; + + dst_pmd = mm_alloc_pmd(dst_mm, state->dst_addr); + if (unlikely(!dst_pmd)) + return -ENOMEM; + + dst_pmdval = pmdp_get_lockless(dst_pmd); + if (unlikely(pmd_none(dst_pmdval)) && + unlikely(__pte_alloc(dst_mm, dst_pmd))) + return -ENOMEM; + + dst_pmdval = pmdp_get_lockless(dst_pmd); + /* + * If the dst_pmd is THP don't override it and just be strict. + * (This includes the case where the PMD used to be THP and + * changed back to none after __pte_alloc().) + */ + if (unlikely(!pmd_present(dst_pmdval) || pmd_leaf(dst_pmdval))) + return -EEXIST; + if (unlikely(pmd_bad(dst_pmdval))) + return -EFAULT; + + state->pmd = dst_pmd; + return 0; +} + /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ static bool mfill_file_over_size(struct vm_area_struct *dst_vma, unsigned long dst_addr) @@ -489,27 +539,6 @@ static int mfill_atomic_pte_poison(struct mfill_state *state) return ret; } -static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) -{ - pgd_t *pgd; - p4d_t *p4d; - pud_t *pud; - - pgd = pgd_offset(mm, address); - p4d = p4d_alloc(mm, pgd, address); - if (!p4d) - return NULL; - pud = pud_alloc(mm, p4d, address); - if (!pud) - return NULL; - /* - * Note that we didn't run this because the pmd was - * missing, the *pmd may be already established and in - * turn it may also be a trans_huge_pmd. - */ - return pmd_alloc(mm, pud, address); -} - #ifdef CONFIG_HUGETLB_PAGE /* * mfill_atomic processing for HUGETLB vmas. Note that this routine is @@ -742,7 +771,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, struct vm_area_struct *dst_vma; long copied = 0; ssize_t err; - pmd_t *dst_pmd; /* * Sanitize the command parameters: @@ -808,41 +836,15 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, while (state.src_addr < src_start + len) { VM_WARN_ON_ONCE(state.dst_addr >= dst_start + len); - pmd_t dst_pmdval; - - dst_pmd = mm_alloc_pmd(dst_mm, state.dst_addr); - if (unlikely(!dst_pmd)) { - err = -ENOMEM; + err = mfill_establish_pmd(&state); + if (err) break; - } - dst_pmdval = pmdp_get_lockless(dst_pmd); - if (unlikely(pmd_none(dst_pmdval)) && - unlikely(__pte_alloc(dst_mm, dst_pmd))) { - err = -ENOMEM; - break; - } - dst_pmdval = pmdp_get_lockless(dst_pmd); - /* - * If the dst_pmd is THP don't override it and just be strict. - * (This includes the case where the PMD used to be THP and - * changed back to none after __pte_alloc().) - */ - if (unlikely(!pmd_present(dst_pmdval) || - pmd_trans_huge(dst_pmdval))) { - err = -EEXIST; - break; - } - if (unlikely(pmd_bad(dst_pmdval))) { - err = -EFAULT; - break; - } /* * For shmem mappings, khugepaged is allowed to remove page * tables under us; pte_offset_map_lock() will deal with that. */ - state.pmd = dst_pmd; err = mfill_atomic_pte(&state); cond_resched(); -- 2.53.0