From: "Mike Rapoport (Microsoft)" <[email protected]> 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) <[email protected]> --- mm/userfaultfd.c | 103 ++++++++++++++++++++++++----------------------- 1 file changed, 53 insertions(+), 50 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 6a0697c93ff4..9dd285b13f3b 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -157,6 +157,57 @@ 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_get_pmd(struct mfill_state *state) +{ + struct mm_struct *dst_mm = state->ctx->mm; + pmd_t *dst_pmd; + pmd_t 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_trans_huge(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 +540,6 @@ 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 +772,6 @@ 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: @@ -809,41 +838,15 @@ 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_get_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(); -- 2.51.0
