diff options
| -rw-r--r-- | drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 8 | ||||
| -rw-r--r-- | mm/gup.c | 40 | ||||
| -rw-r--r-- | mm/huge_memory.c | 7 |
3 files changed, 9 insertions, 46 deletions
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c index c31a6744daee..853184db8e83 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c @@ -599,14 +599,6 @@ static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj) GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); - /* - * Using __get_user_pages_fast() with a read-only - * access is questionable. A read-only page may be - * COW-broken, and then this might end up giving - * the wrong side of the COW.. - * - * We may or may not care. - */ if (pvec) { /* defer to worker if malloc fails */ if (!i915_gem_object_is_readonly(obj)) @@ -381,22 +381,13 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, } /* - * FOLL_FORCE or a forced COW break can write even to unwritable pte's, - * but only after we've gone through a COW cycle and they are dirty. + * FOLL_FORCE can write to even unwritable pte's, but only + * after we've gone through a COW cycle and they are dirty. */ static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) { - return pte_write(pte) || ((flags & FOLL_COW) && pte_dirty(pte)); -} - -/* - * A (separate) COW fault might break the page the other way and - * get_user_pages() would return the page from what is now the wrong - * VM. So we need to force a COW break at GUP time even for reads. - */ -static inline bool should_force_cow_break(struct vm_area_struct *vma, unsigned int flags) -{ - return is_cow_mapping(vma->vm_flags) && (flags & (FOLL_GET | FOLL_PIN)); + return pte_write(pte) || + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); } static struct page *follow_page_pte(struct vm_area_struct *vma, @@ -1075,11 +1066,9 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, goto out; } if (is_vm_hugetlb_page(vma)) { - if (should_force_cow_break(vma, foll_flags)) - foll_flags |= FOLL_WRITE; i = follow_hugetlb_page(mm, vma, pages, vmas, &start, &nr_pages, i, - foll_flags, locked); + gup_flags, locked); if (locked && *locked == 0) { /* * We've got a VM_FAULT_RETRY @@ -1093,10 +1082,6 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, continue; } } - - if (should_force_cow_break(vma, foll_flags)) - foll_flags |= FOLL_WRITE; - retry: /* * If we have a pending SIGKILL, don't keep faulting pages and @@ -2763,19 +2748,6 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, return -EFAULT; /* - * The FAST_GUP case requires FOLL_WRITE even for pure reads, - * because get_user_pages() may need to cause an early COW in - * order to avoid confusing the normal COW routines. So only - * targets that are already writable are safe to do by just - * looking at the page tables. - * - * NOTE! With FOLL_FAST_ONLY we allow read-only gup_fast() here, - * because there is no slow path to fall back on. But you'd - * better be careful about possible COW pages - you'll get _a_ - * COW page, but not necessarily the one you intended to get - * depending on what COW event happens after this. COW may break - * the page copy in a random direction. - * * Disable interrupts. The nested form is used, in order to allow * full, general purpose use of this routine. * @@ -2788,8 +2760,6 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages, */ if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) { unsigned long fast_flags = gup_flags; - if (!(gup_flags & FOLL_FAST_ONLY)) - fast_flags |= FOLL_WRITE; local_irq_save(flags); gup_pgd_range(addr, end, fast_flags, pages, &nr_pinned); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 78c84bee7e29..6f74f3d93839 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1312,12 +1312,13 @@ fallback: } /* - * FOLL_FORCE or a forced COW break can write even to unwritable pmd's, - * but only after we've gone through a COW cycle and they are dirty. + * FOLL_FORCE can write to even unwritable pmd's, but only + * after we've gone through a COW cycle and they are dirty. */ static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) { - return pmd_write(pmd) || ((flags & FOLL_COW) && pmd_dirty(pmd)); + return pmd_write(pmd) || + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); } struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, |