Merge drm/drm-fixes into drm-misc-fixes

7.0-rc1 was just released, let's merge it to kick the new release cycle.

Signed-off-by: Maxime Ripard <mripard@kernel.org>

1 files changed, 315 insertions, 58 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6f959d8ca4b4..5be3d8a8f806 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_MM_H
 #define _LINUX_MM_H
 
+#include <linux/args.h>
 #include <linux/errno.h>
 #include <linux/mmdebug.h>
 #include <linux/gfp.h>
@@ -36,6 +37,7 @@
 #include <linux/rcuwait.h>
 #include <linux/bitmap.h>
 #include <linux/bitops.h>
+#include <linux/iommu-debug-pagealloc.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -45,6 +47,7 @@ struct pt_regs;
 struct folio_batch;
 
 void arch_mm_preinit(void);
+void mm_core_init_early(void);
 void mm_core_init(void);
 void init_mm_internals(void);
 
@@ -359,7 +362,7 @@ enum {
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT2, HIGH_ARCH_2),
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT3, HIGH_ARCH_3),
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT4, HIGH_ARCH_4),
-#if defined(CONFIG_X86_USER_SHADOW_STACK)
+#if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_RISCV_USER_CFI)
 	/*
 	 * VM_SHADOW_STACK should not be set with VM_SHARED because of lack of
 	 * support core mm.
@@ -460,7 +463,8 @@ enum {
 #define VM_PKEY_BIT4  VM_NONE
 #endif /* CONFIG_ARCH_PKEY_BITS > 4 */
 #endif /* CONFIG_ARCH_HAS_PKEYS */
-#if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_ARM64_GCS)
+#if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_ARM64_GCS) || \
+	defined(CONFIG_RISCV_USER_CFI)
 #define VM_SHADOW_STACK	INIT_VM_FLAG(SHADOW_STACK)
 #else
 #define VM_SHADOW_STACK	VM_NONE
@@ -548,17 +552,18 @@ enum {
 /*
  * Physically remapped pages are special. Tell the
  * rest of the world about it:
- *   VM_IO tells people not to look at these pages
+ *   IO tells people not to look at these pages
  *	(accesses can have side effects).
- *   VM_PFNMAP tells the core MM that the base pages are just
+ *   PFNMAP tells the core MM that the base pages are just
  *	raw PFN mappings, and do not have a "struct page" associated
  *	with them.
- *   VM_DONTEXPAND
+ *   DONTEXPAND
  *      Disable vma merging and expanding with mremap().
- *   VM_DONTDUMP
+ *   DONTDUMP
  *      Omit vma from core dump, even when VM_IO turned off.
  */
-#define VM_REMAP_FLAGS (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
+#define VMA_REMAP_FLAGS mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,	\
+				     VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT)
 
 /* This mask prevents VMA from being scanned with khugepaged */
 #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
@@ -608,7 +613,11 @@ enum {
 /*
  * Flags which should result in page tables being copied on fork. These are
  * flags which indicate that the VMA maps page tables which cannot be
- * reconsistuted upon page fault, so necessitate page table copying upon
+ * reconsistuted upon page fault, so necessitate page table copying upon fork.
+ *
+ * Note that these flags should be compared with the DESTINATION VMA not the
+ * source, as VM_UFFD_WP may not be propagated to destination, while all other
+ * flags will be.
  *
  * VM_PFNMAP / VM_MIXEDMAP - These contain kernel-mapped data which cannot be
  *                           reasonably reconstructed on page fault.
@@ -938,7 +947,7 @@ static inline void vm_flags_reset_once(struct vm_area_struct *vma,
 	 * system word.
 	 */
 	if (NUM_VMA_FLAG_BITS > BITS_PER_LONG) {
-		unsigned long *bitmap = ACCESS_PRIVATE(&vma->flags, __vma_flags);
+		unsigned long *bitmap = vma->flags.__vma_flags;
 
 		bitmap_zero(&bitmap[1], NUM_VMA_FLAG_BITS - BITS_PER_LONG);
 	}
@@ -982,8 +991,7 @@ static inline void vm_flags_mod(struct vm_area_struct *vma,
 	__vm_flags_mod(vma, set, clear);
 }
 
-static inline bool __vma_flag_atomic_valid(struct vm_area_struct *vma,
-					   vma_flag_t bit)
+static inline bool __vma_atomic_valid_flag(struct vm_area_struct *vma, vma_flag_t bit)
 {
 	const vm_flags_t mask = BIT((__force int)bit);
 
@@ -998,16 +1006,12 @@ static inline bool __vma_flag_atomic_valid(struct vm_area_struct *vma,
  * Set VMA flag atomically. Requires only VMA/mmap read lock. Only specific
  * valid flags are allowed to do this.
  */
-static inline void vma_flag_set_atomic(struct vm_area_struct *vma,
-				       vma_flag_t bit)
+static inline void vma_set_atomic_flag(struct vm_area_struct *vma, vma_flag_t bit)
 {
-	unsigned long *bitmap = ACCESS_PRIVATE(&vma->flags, __vma_flags);
-
-	/* mmap read lock/VMA read lock must be held. */
-	if (!rwsem_is_locked(&vma->vm_mm->mmap_lock))
-		vma_assert_locked(vma);
+	unsigned long *bitmap = vma->flags.__vma_flags;
 
-	if (__vma_flag_atomic_valid(vma, bit))
+	vma_assert_stabilised(vma);
+	if (__vma_atomic_valid_flag(vma, bit))
 		set_bit((__force int)bit, bitmap);
 }
 
@@ -1018,15 +1022,211 @@ static inline void vma_flag_set_atomic(struct vm_area_struct *vma,
  * This is necessarily racey, so callers must ensure that serialisation is
  * achieved through some other means, or that races are permissible.
  */
-static inline bool vma_flag_test_atomic(struct vm_area_struct *vma,
-					vma_flag_t bit)
+static inline bool vma_test_atomic_flag(struct vm_area_struct *vma, vma_flag_t bit)
 {
-	if (__vma_flag_atomic_valid(vma, bit))
+	if (__vma_atomic_valid_flag(vma, bit))
 		return test_bit((__force int)bit, &vma->vm_flags);
 
 	return false;
 }
 
+/* Set an individual VMA flag in flags, non-atomically. */
+static inline void vma_flag_set(vma_flags_t *flags, vma_flag_t bit)
+{
+	unsigned long *bitmap = flags->__vma_flags;
+
+	__set_bit((__force int)bit, bitmap);
+}
+
+static inline vma_flags_t __mk_vma_flags(size_t count, const vma_flag_t *bits)
+{
+	vma_flags_t flags;
+	int i;
+
+	vma_flags_clear_all(&flags);
+	for (i = 0; i < count; i++)
+		vma_flag_set(&flags, bits[i]);
+	return flags;
+}
+
+/*
+ * Helper macro which bitwise-or combines the specified input flags into a
+ * vma_flags_t bitmap value. E.g.:
+ *
+ * vma_flags_t flags = mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,
+ * 		VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT);
+ *
+ * The compiler cleverly optimises away all of the work and this ends up being
+ * equivalent to aggregating the values manually.
+ */
+#define mk_vma_flags(...) __mk_vma_flags(COUNT_ARGS(__VA_ARGS__), \
+					 (const vma_flag_t []){__VA_ARGS__})
+
+/*  Test each of to_test flags in flags, non-atomically. */
+static __always_inline bool vma_flags_test_mask(const vma_flags_t *flags,
+		vma_flags_t to_test)
+{
+	const unsigned long *bitmap = flags->__vma_flags;
+	const unsigned long *bitmap_to_test = to_test.__vma_flags;
+
+	return bitmap_intersects(bitmap_to_test, bitmap, NUM_VMA_FLAG_BITS);
+}
+
+/*
+ * Test whether any specified VMA flag is set, e.g.:
+ *
+ * if (vma_flags_test(flags, VMA_READ_BIT, VMA_MAYREAD_BIT)) { ... }
+ */
+#define vma_flags_test(flags, ...) \
+	vma_flags_test_mask(flags, mk_vma_flags(__VA_ARGS__))
+
+/* Test that ALL of the to_test flags are set, non-atomically. */
+static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags,
+		vma_flags_t to_test)
+{
+	const unsigned long *bitmap = flags->__vma_flags;
+	const unsigned long *bitmap_to_test = to_test.__vma_flags;
+
+	return bitmap_subset(bitmap_to_test, bitmap, NUM_VMA_FLAG_BITS);
+}
+
+/*
+ * Test whether ALL specified VMA flags are set, e.g.:
+ *
+ * if (vma_flags_test_all(flags, VMA_READ_BIT, VMA_MAYREAD_BIT)) { ... }
+ */
+#define vma_flags_test_all(flags, ...) \
+	vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__))
+
+/* Set each of the to_set flags in flags, non-atomically. */
+static __always_inline void vma_flags_set_mask(vma_flags_t *flags, vma_flags_t to_set)
+{
+	unsigned long *bitmap = flags->__vma_flags;
+	const unsigned long *bitmap_to_set = to_set.__vma_flags;
+
+	bitmap_or(bitmap, bitmap, bitmap_to_set, NUM_VMA_FLAG_BITS);
+}
+
+/*
+ * Set all specified VMA flags, e.g.:
+ *
+ * vma_flags_set(&flags, VMA_READ_BIT, VMA_WRITE_BIT, VMA_EXEC_BIT);
+ */
+#define vma_flags_set(flags, ...) \
+	vma_flags_set_mask(flags, mk_vma_flags(__VA_ARGS__))
+
+/* Clear all of the to-clear flags in flags, non-atomically. */
+static __always_inline void vma_flags_clear_mask(vma_flags_t *flags, vma_flags_t to_clear)
+{
+	unsigned long *bitmap = flags->__vma_flags;
+	const unsigned long *bitmap_to_clear = to_clear.__vma_flags;
+
+	bitmap_andnot(bitmap, bitmap, bitmap_to_clear, NUM_VMA_FLAG_BITS);
+}
+
+/*
+ * Clear all specified individual flags, e.g.:
+ *
+ * vma_flags_clear(&flags, VMA_READ_BIT, VMA_WRITE_BIT, VMA_EXEC_BIT);
+ */
+#define vma_flags_clear(flags, ...) \
+	vma_flags_clear_mask(flags, mk_vma_flags(__VA_ARGS__))
+
+/*
+ * Helper to test that ALL specified flags are set in a VMA.
+ *
+ * Note: appropriate locks must be held, this function does not acquire them for
+ * you.
+ */
+static inline bool vma_test_all_flags_mask(const struct vm_area_struct *vma,
+					   vma_flags_t flags)
+{
+	return vma_flags_test_all_mask(&vma->flags, flags);
+}
+
+/*
+ * Helper macro for checking that ALL specified flags are set in a VMA, e.g.:
+ *
+ * if (vma_test_all_flags(vma, VMA_READ_BIT, VMA_MAYREAD_BIT) { ... }
+ */
+#define vma_test_all_flags(vma, ...) \
+	vma_test_all_flags_mask(vma, mk_vma_flags(__VA_ARGS__))
+
+/*
+ * Helper to set all VMA flags in a VMA.
+ *
+ * Note: appropriate locks must be held, this function does not acquire them for
+ * you.
+ */
+static inline void vma_set_flags_mask(struct vm_area_struct *vma,
+				      vma_flags_t flags)
+{
+	vma_flags_set_mask(&vma->flags, flags);
+}
+
+/*
+ * Helper macro for specifying VMA flags in a VMA, e.g.:
+ *
+ * vma_set_flags(vma, VMA_IO_BIT, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT,
+ * 		VMA_DONTDUMP_BIT);
+ *
+ * Note: appropriate locks must be held, this function does not acquire them for
+ * you.
+ */
+#define vma_set_flags(vma, ...) \
+	vma_set_flags_mask(vma, mk_vma_flags(__VA_ARGS__))
+
+/* Helper to test all VMA flags in a VMA descriptor. */
+static inline bool vma_desc_test_flags_mask(const struct vm_area_desc *desc,
+					    vma_flags_t flags)
+{
+	return vma_flags_test_mask(&desc->vma_flags, flags);
+}
+
+/*
+ * Helper macro for testing VMA flags for an input pointer to a struct
+ * vm_area_desc object describing a proposed VMA, e.g.:
+ *
+ * if (vma_desc_test_flags(desc, VMA_IO_BIT, VMA_PFNMAP_BIT,
+ *		VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT)) { ... }
+ */
+#define vma_desc_test_flags(desc, ...) \
+	vma_desc_test_flags_mask(desc, mk_vma_flags(__VA_ARGS__))
+
+/* Helper to set all VMA flags in a VMA descriptor. */
+static inline void vma_desc_set_flags_mask(struct vm_area_desc *desc,
+					   vma_flags_t flags)
+{
+	vma_flags_set_mask(&desc->vma_flags, flags);
+}
+
+/*
+ * Helper macro for specifying VMA flags for an input pointer to a struct
+ * vm_area_desc object describing a proposed VMA, e.g.:
+ *
+ * vma_desc_set_flags(desc, VMA_IO_BIT, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT,
+ * 		VMA_DONTDUMP_BIT);
+ */
+#define vma_desc_set_flags(desc, ...) \
+	vma_desc_set_flags_mask(desc, mk_vma_flags(__VA_ARGS__))
+
+/* Helper to clear all VMA flags in a VMA descriptor. */
+static inline void vma_desc_clear_flags_mask(struct vm_area_desc *desc,
+					     vma_flags_t flags)
+{
+	vma_flags_clear_mask(&desc->vma_flags, flags);
+}
+
+/*
+ * Helper macro for clearing VMA flags for an input pointer to a struct
+ * vm_area_desc object describing a proposed VMA, e.g.:
+ *
+ * vma_desc_clear_flags(desc, VMA_IO_BIT, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT,
+ * 		VMA_DONTDUMP_BIT);
+ */
+#define vma_desc_clear_flags(desc, ...) \
+	vma_desc_clear_flags_mask(desc, mk_vma_flags(__VA_ARGS__))
+
 static inline void vma_set_anonymous(struct vm_area_struct *vma)
 {
 	vma->vm_ops = NULL;
@@ -1092,15 +1292,20 @@ static inline bool vma_is_accessible(const struct vm_area_struct *vma)
 	return vma->vm_flags & VM_ACCESS_FLAGS;
 }
 
-static inline bool is_shared_maywrite(vm_flags_t vm_flags)
+static inline bool is_shared_maywrite_vm_flags(vm_flags_t vm_flags)
 {
 	return (vm_flags & (VM_SHARED | VM_MAYWRITE)) ==
 		(VM_SHARED | VM_MAYWRITE);
 }
 
+static inline bool is_shared_maywrite(const vma_flags_t *flags)
+{
+	return vma_flags_test_all(flags, VMA_SHARED_BIT, VMA_MAYWRITE_BIT);
+}
+
 static inline bool vma_is_shared_maywrite(const struct vm_area_struct *vma)
 {
-	return is_shared_maywrite(vma->vm_flags);
+	return is_shared_maywrite(&vma->flags);
 }
 
 static inline
@@ -1728,6 +1933,14 @@ static inline bool is_cow_mapping(vm_flags_t flags)
 	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
 }
 
+static inline bool vma_desc_is_cow_mapping(struct vm_area_desc *desc)
+{
+	const vma_flags_t *flags = &desc->vma_flags;
+
+	return vma_flags_test(flags, VMA_MAYWRITE_BIT) &&
+		!vma_flags_test(flags, VMA_SHARED_BIT);
+}
+
 #ifndef CONFIG_MMU
 static inline bool is_nommu_shared_mapping(vm_flags_t flags)
 {
@@ -1741,6 +1954,11 @@ static inline bool is_nommu_shared_mapping(vm_flags_t flags)
 	 */
 	return flags & (VM_MAYSHARE | VM_MAYOVERLAY);
 }
+
+static inline bool is_nommu_shared_vma_flags(const vma_flags_t *flags)
+{
+	return vma_flags_test(flags, VMA_MAYSHARE_BIT, VMA_MAYOVERLAY_BIT);
+}
 #endif
 
 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
@@ -2623,10 +2841,6 @@ static inline void zap_vma_pages(struct vm_area_struct *vma)
 	zap_page_range_single(vma, vma->vm_start,
 			      vma->vm_end - vma->vm_start, NULL);
 }
-void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
-		struct vm_area_struct *start_vma, unsigned long start,
-		unsigned long end, unsigned long tree_end);
-
 struct mmu_notifier_range;
 
 void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
@@ -2901,6 +3115,13 @@ static inline unsigned long get_mm_rss(struct mm_struct *mm)
 		get_mm_counter(mm, MM_SHMEMPAGES);
 }
 
+static inline unsigned long get_mm_rss_sum(struct mm_struct *mm)
+{
+	return get_mm_counter_sum(mm, MM_FILEPAGES) +
+		get_mm_counter_sum(mm, MM_ANONPAGES) +
+		get_mm_counter_sum(mm, MM_SHMEMPAGES);
+}
+
 static inline unsigned long get_mm_hiwater_rss(struct mm_struct *mm)
 {
 	return max(mm->hiwater_rss, get_mm_rss(mm));
@@ -2975,15 +3196,8 @@ static inline pud_t pud_mkspecial(pud_t pud)
 }
 #endif	/* CONFIG_ARCH_SUPPORTS_PUD_PFNMAP */
 
-extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
-			       spinlock_t **ptl);
-static inline pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
-				    spinlock_t **ptl)
-{
-	pte_t *ptep;
-	__cond_lock(*ptl, ptep = __get_locked_pte(mm, addr, ptl));
-	return ptep;
-}
+extern pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
+			     spinlock_t **ptl);
 
 #ifdef __PAGETABLE_P4D_FOLDED
 static inline int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd,
@@ -3337,31 +3551,15 @@ static inline bool pagetable_pte_ctor(struct mm_struct *mm,
 	return true;
 }
 
-pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
-static inline pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr,
-			pmd_t *pmdvalp)
-{
-	pte_t *pte;
+pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
 
-	__cond_lock(RCU, pte = ___pte_offset_map(pmd, addr, pmdvalp));
-	return pte;
-}
 static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
 {
 	return __pte_offset_map(pmd, addr, NULL);
 }
 
-pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, spinlock_t **ptlp);
-static inline pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, spinlock_t **ptlp)
-{
-	pte_t *pte;
-
-	__cond_lock(RCU, __cond_lock(*ptlp,
-			pte = __pte_offset_map_lock(mm, pmd, addr, ptlp)));
-	return pte;
-}
+pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
+			   unsigned long addr, spinlock_t **ptlp);
 
 pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd,
 				unsigned long addr, spinlock_t **ptlp);
@@ -3536,7 +3734,7 @@ static inline unsigned long get_num_physpages(void)
 }
 
 /*
- * Using memblock node mappings, an architecture may initialise its
+ * FIXME: Using memblock node mappings, an architecture may initialise its
  * zones, allocate the backing mem_map and account for memory holes in an
  * architecture independent manner.
  *
@@ -3551,7 +3749,7 @@ static inline unsigned long get_num_physpages(void)
  *	memblock_add_node(base, size, nid, MEMBLOCK_NONE)
  * free_area_init(max_zone_pfns);
  */
-void free_area_init(unsigned long *max_zone_pfn);
+void arch_zone_limits_init(unsigned long *max_zone_pfn);
 unsigned long node_map_pfn_alignment(void);
 extern unsigned long absent_pages_in_range(unsigned long start_pfn,
 						unsigned long end_pfn);
@@ -4133,12 +4331,16 @@ extern void __kernel_map_pages(struct page *page, int numpages, int enable);
 #ifdef CONFIG_DEBUG_PAGEALLOC
 static inline void debug_pagealloc_map_pages(struct page *page, int numpages)
 {
+	iommu_debug_check_unmapped(page, numpages);
+
 	if (debug_pagealloc_enabled_static())
 		__kernel_map_pages(page, numpages, 1);
 }
 
 static inline void debug_pagealloc_unmap_pages(struct page *page, int numpages)
 {
+	iommu_debug_check_unmapped(page, numpages);
+
 	if (debug_pagealloc_enabled_static())
 		__kernel_map_pages(page, numpages, 0);
 }
@@ -4194,6 +4396,61 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
 				unsigned int order) {}
 #endif	/* CONFIG_DEBUG_PAGEALLOC */
 
+#ifndef clear_pages
+/**
+ * clear_pages() - clear a page range for kernel-internal use.
+ * @addr: start address
+ * @npages: number of pages
+ *
+ * Use clear_user_pages() instead when clearing a page range to be
+ * mapped to user space.
+ *
+ * Does absolutely no exception handling.
+ *
+ * Note that even though the clearing operation is preemptible, clear_pages()
+ * does not (and on architectures where it reduces to a few long-running
+ * instructions, might not be able to) call cond_resched() to check if
+ * rescheduling is required.
+ *
+ * When running under preemptible models this is not a problem. Under
+ * cooperatively scheduled models, however, the caller is expected to
+ * limit @npages to no more than PROCESS_PAGES_NON_PREEMPT_BATCH.
+ */
+static inline void clear_pages(void *addr, unsigned int npages)
+{
+	do {
+		clear_page(addr);
+		addr += PAGE_SIZE;
+	} while (--npages);
+}
+#endif
+
+#ifndef PROCESS_PAGES_NON_PREEMPT_BATCH
+#ifdef clear_pages
+/*
+ * The architecture defines clear_pages(), and we assume that it is
+ * generally "fast". So choose a batch size large enough to allow the processor
+ * headroom for optimizing the operation and yet small enough that we see
+ * reasonable preemption latency for when this optimization is not possible
+ * (ex. slow microarchitectures, memory bandwidth saturation.)
+ *
+ * With a value of 32MB and assuming a memory bandwidth of ~10GBps, this should
+ * result in worst case preemption latency of around 3ms when clearing pages.
+ *
+ * (See comment above clear_pages() for why preemption latency is a concern
+ * here.)
+ */
+#define PROCESS_PAGES_NON_PREEMPT_BATCH		(SZ_32M >> PAGE_SHIFT)
+#else /* !clear_pages */
+/*
+ * The architecture does not provide a clear_pages() implementation. Assume
+ * that clear_page() -- which clear_pages() will fallback to -- is relatively
+ * slow and choose a small value for PROCESS_PAGES_NON_PREEMPT_BATCH.
+ */
+#define PROCESS_PAGES_NON_PREEMPT_BATCH		1
+#endif
+#endif
+
 #ifdef __HAVE_ARCH_GATE_AREA
 extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
 extern int in_gate_area_no_mm(unsigned long addr);