Merge branch 'akpm' (patches from Andrew)

Merge misc updates from Andrew Morton:

 - a few random little subsystems

 - almost all of the MM patches which are staged ahead of linux-next
   material. I'll trickle to post-linux-next work in as the dependents
   get merged up.

Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (200 commits)
  mm: cleanup kstrto*() usage
  mm: fix fall-through warnings for Clang
  mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
  mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
  mm:backing-dev: use sysfs_emit in macro defining functions
  mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
  mm: use sysfs_emit for struct kobject * uses
  mm: fix kernel-doc markups
  zram: break the strict dependency from lzo
  zram: add stat to gather incompressible pages since zram set up
  zram: support page writeback
  mm/process_vm_access: remove redundant initialization of iov_r
  mm/zsmalloc.c: rework the list_add code in insert_zspage()
  mm/zswap: move to use crypto_acomp API for hardware acceleration
  mm/zswap: fix passing zero to 'PTR_ERR' warning
  mm/zswap: make struct kernel_param_ops definitions const
  userfaultfd/selftests: hint the test runner on required privilege
  userfaultfd/selftests: fix retval check for userfaultfd_open()
  userfaultfd/selftests: always dump something in modes
  userfaultfd: selftests: make __{s,u}64 format specifiers portable
  ...

1 files changed, 123 insertions, 203 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 44b0c6b89602..e4c224cd9661 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -123,6 +123,28 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page,
 	return NULL;
 }
 
+static void put_compound_head(struct page *page, int refs, unsigned int flags)
+{
+	if (flags & FOLL_PIN) {
+		mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
+				    refs);
+
+		if (hpage_pincount_available(page))
+			hpage_pincount_sub(page, refs);
+		else
+			refs *= GUP_PIN_COUNTING_BIAS;
+	}
+
+	VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
+	/*
+	 * Calling put_page() for each ref is unnecessarily slow. Only the last
+	 * ref needs a put_page().
+	 */
+	if (refs > 1)
+		page_ref_sub(page, refs - 1);
+	put_page(page);
+}
+
 /**
  * try_grab_page() - elevate a page's refcount by a flag-dependent amount
  *
@@ -177,41 +199,6 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags)
 	return true;
 }
 
-#ifdef CONFIG_DEV_PAGEMAP_OPS
-static bool __unpin_devmap_managed_user_page(struct page *page)
-{
-	int count, refs = 1;
-
-	if (!page_is_devmap_managed(page))
-		return false;
-
-	if (hpage_pincount_available(page))
-		hpage_pincount_sub(page, 1);
-	else
-		refs = GUP_PIN_COUNTING_BIAS;
-
-	count = page_ref_sub_return(page, refs);
-
-	mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1);
-	/*
-	 * devmap page refcounts are 1-based, rather than 0-based: if
-	 * refcount is 1, then the page is free and the refcount is
-	 * stable because nobody holds a reference on the page.
-	 */
-	if (count == 1)
-		free_devmap_managed_page(page);
-	else if (!count)
-		__put_page(page);
-
-	return true;
-}
-#else
-static bool __unpin_devmap_managed_user_page(struct page *page)
-{
-	return false;
-}
-#endif /* CONFIG_DEV_PAGEMAP_OPS */
-
 /**
  * unpin_user_page() - release a dma-pinned page
  * @page:            pointer to page to be released
@@ -223,28 +210,7 @@ static bool __unpin_devmap_managed_user_page(struct page *page)
  */
 void unpin_user_page(struct page *page)
 {
-	int refs = 1;
-
-	page = compound_head(page);
-
-	/*
-	 * For devmap managed pages we need to catch refcount transition from
-	 * GUP_PIN_COUNTING_BIAS to 1, when refcount reach one it means the
-	 * page is free and we need to inform the device driver through
-	 * callback. See include/linux/memremap.h and HMM for details.
-	 */
-	if (__unpin_devmap_managed_user_page(page))
-		return;
-
-	if (hpage_pincount_available(page))
-		hpage_pincount_sub(page, 1);
-	else
-		refs = GUP_PIN_COUNTING_BIAS;
-
-	if (page_ref_sub_and_test(page, refs))
-		__put_page(page);
-
-	mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1);
+	put_compound_head(compound_head(page), 1, FOLL_PIN);
 }
 EXPORT_SYMBOL(unpin_user_page);
 
@@ -923,6 +889,9 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
 	if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma))
 		return -EFAULT;
 
+	if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma))
+		return -EOPNOTSUPP;
+
 	if (write) {
 		if (!(vm_flags & VM_WRITE)) {
 			if (!(gup_flags & FOLL_FORCE))
@@ -1060,10 +1029,14 @@ static long __get_user_pages(struct mm_struct *mm,
 				goto next_page;
 			}
 
-			if (!vma || check_vma_flags(vma, gup_flags)) {
+			if (!vma) {
 				ret = -EFAULT;
 				goto out;
 			}
+			ret = check_vma_flags(vma, gup_flags);
+			if (ret)
+				goto out;
+
 			if (is_vm_hugetlb_page(vma)) {
 				i = follow_hugetlb_page(mm, vma, pages, vmas,
 						&start, &nr_pages, i,
@@ -1567,26 +1540,6 @@ struct page *get_dump_page(unsigned long addr)
 }
 #endif /* CONFIG_ELF_CORE */
 
-#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
-static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
-{
-	long i;
-	struct vm_area_struct *vma_prev = NULL;
-
-	for (i = 0; i < nr_pages; i++) {
-		struct vm_area_struct *vma = vmas[i];
-
-		if (vma == vma_prev)
-			continue;
-
-		vma_prev = vma;
-
-		if (vma_is_fsdax(vma))
-			return true;
-	}
-	return false;
-}
-
 #ifdef CONFIG_CMA
 static long check_and_migrate_cma_pages(struct mm_struct *mm,
 					unsigned long start,
@@ -1705,63 +1658,23 @@ static long __gup_longterm_locked(struct mm_struct *mm,
 				  struct vm_area_struct **vmas,
 				  unsigned int gup_flags)
 {
-	struct vm_area_struct **vmas_tmp = vmas;
 	unsigned long flags = 0;
-	long rc, i;
-
-	if (gup_flags & FOLL_LONGTERM) {
-		if (!pages)
-			return -EINVAL;
+	long rc;
 
-		if (!vmas_tmp) {
-			vmas_tmp = kcalloc(nr_pages,
-					   sizeof(struct vm_area_struct *),
-					   GFP_KERNEL);
-			if (!vmas_tmp)
-				return -ENOMEM;
-		}
+	if (gup_flags & FOLL_LONGTERM)
 		flags = memalloc_nocma_save();
-	}
 
-	rc = __get_user_pages_locked(mm, start, nr_pages, pages,
-				     vmas_tmp, NULL, gup_flags);
+	rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas, NULL,
+				     gup_flags);
 
 	if (gup_flags & FOLL_LONGTERM) {
-		if (rc < 0)
-			goto out;
-
-		if (check_dax_vmas(vmas_tmp, rc)) {
-			if (gup_flags & FOLL_PIN)
-				unpin_user_pages(pages, rc);
-			else
-				for (i = 0; i < rc; i++)
-					put_page(pages[i]);
-			rc = -EOPNOTSUPP;
-			goto out;
-		}
-
-		rc = check_and_migrate_cma_pages(mm, start, rc, pages,
-						 vmas_tmp, gup_flags);
-out:
+		if (rc > 0)
+			rc = check_and_migrate_cma_pages(mm, start, rc, pages,
+							 vmas, gup_flags);
 		memalloc_nocma_restore(flags);
 	}
-
-	if (vmas_tmp != vmas)
-		kfree(vmas_tmp);
 	return rc;
 }
-#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
-static __always_inline long __gup_longterm_locked(struct mm_struct *mm,
-						  unsigned long start,
-						  unsigned long nr_pages,
-						  struct page **pages,
-						  struct vm_area_struct **vmas,
-						  unsigned int flags)
-{
-	return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
-				       NULL, flags);
-}
-#endif /* CONFIG_FS_DAX || CONFIG_CMA */
 
 static bool is_valid_gup_flags(unsigned int gup_flags)
 {
@@ -1932,7 +1845,19 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
 EXPORT_SYMBOL(get_user_pages);
 
 /**
- * get_user_pages_locked() is suitable to replace the form:
+ * get_user_pages_locked() - variant of get_user_pages()
+ *
+ * @start:      starting user address
+ * @nr_pages:   number of pages from start to pin
+ * @gup_flags:  flags modifying lookup behaviour
+ * @pages:      array that receives pointers to the pages pinned.
+ *              Should be at least nr_pages long. Or NULL, if caller
+ *              only intends to ensure the pages are faulted in.
+ * @locked:     pointer to lock flag indicating whether lock is held and
+ *              subsequently whether VM_FAULT_RETRY functionality can be
+ *              utilised. Lock must initially be held.
+ *
+ * It is suitable to replace the form:
  *
  *      mmap_read_lock(mm);
  *      do_something()
@@ -1948,16 +1873,6 @@ EXPORT_SYMBOL(get_user_pages);
  *      if (locked)
  *          mmap_read_unlock(mm);
  *
- * @start:      starting user address
- * @nr_pages:   number of pages from start to pin
- * @gup_flags:  flags modifying lookup behaviour
- * @pages:      array that receives pointers to the pages pinned.
- *              Should be at least nr_pages long. Or NULL, if caller
- *              only intends to ensure the pages are faulted in.
- * @locked:     pointer to lock flag indicating whether lock is held and
- *              subsequently whether VM_FAULT_RETRY functionality can be
- *              utilised. Lock must initially be held.
- *
  * We can leverage the VM_FAULT_RETRY functionality in the page fault
  * paths better by using either get_user_pages_locked() or
  * get_user_pages_unlocked().
@@ -2063,28 +1978,6 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
  */
 #ifdef CONFIG_HAVE_FAST_GUP
 
-static void put_compound_head(struct page *page, int refs, unsigned int flags)
-{
-	if (flags & FOLL_PIN) {
-		mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED,
-				    refs);
-
-		if (hpage_pincount_available(page))
-			hpage_pincount_sub(page, refs);
-		else
-			refs *= GUP_PIN_COUNTING_BIAS;
-	}
-
-	VM_BUG_ON_PAGE(page_ref_count(page) < refs, page);
-	/*
-	 * Calling put_page() for each ref is unnecessarily slow. Only the last
-	 * ref needs a put_page().
-	 */
-	if (refs > 1)
-		page_ref_sub(page, refs - 1);
-	put_page(page);
-}
-
 static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
 					    unsigned int flags,
 					    struct page **pages)
@@ -2621,13 +2514,61 @@ static int __gup_longterm_unlocked(unsigned long start, int nr_pages,
 	return ret;
 }
 
-static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
+static unsigned long lockless_pages_from_mm(unsigned long start,
+					    unsigned long end,
+					    unsigned int gup_flags,
+					    struct page **pages)
+{
+	unsigned long flags;
+	int nr_pinned = 0;
+	unsigned seq;
+
+	if (!IS_ENABLED(CONFIG_HAVE_FAST_GUP) ||
+	    !gup_fast_permitted(start, end))
+		return 0;
+
+	if (gup_flags & FOLL_PIN) {
+		seq = raw_read_seqcount(&current->mm->write_protect_seq);
+		if (seq & 1)
+			return 0;
+	}
+
+	/*
+	 * Disable interrupts. The nested form is used, in order to allow full,
+	 * general purpose use of this routine.
+	 *
+	 * With interrupts disabled, we block page table pages from being freed
+	 * from under us. See struct mmu_table_batch comments in
+	 * include/asm-generic/tlb.h for more details.
+	 *
+	 * We do not adopt an rcu_read_lock() here as we also want to block IPIs
+	 * that come from THPs splitting.
+	 */
+	local_irq_save(flags);
+	gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
+	local_irq_restore(flags);
+
+	/*
+	 * When pinning pages for DMA there could be a concurrent write protect
+	 * from fork() via copy_page_range(), in this case always fail fast GUP.
+	 */
+	if (gup_flags & FOLL_PIN) {
+		if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
+			unpin_user_pages(pages, nr_pinned);
+			return 0;
+		}
+	}
+	return nr_pinned;
+}
+
+static int internal_get_user_pages_fast(unsigned long start,
+					unsigned long nr_pages,
 					unsigned int gup_flags,
 					struct page **pages)
 {
-	unsigned long addr, len, end;
-	unsigned long flags;
-	int nr_pinned = 0, ret = 0;
+	unsigned long len, end;
+	unsigned long nr_pinned;
+	int ret;
 
 	if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM |
 				       FOLL_FORCE | FOLL_PIN | FOLL_GET |
@@ -2641,54 +2582,33 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
 		might_lock_read(&current->mm->mmap_lock);
 
 	start = untagged_addr(start) & PAGE_MASK;
-	addr = start;
-	len = (unsigned long) nr_pages << PAGE_SHIFT;
-	end = start + len;
-
-	if (end <= start)
+	len = nr_pages << PAGE_SHIFT;
+	if (check_add_overflow(start, len, &end))
 		return 0;
 	if (unlikely(!access_ok((void __user *)start, len)))
 		return -EFAULT;
 
-	/*
-	 * Disable interrupts. The nested form is used, in order to allow
-	 * full, general purpose use of this routine.
-	 *
-	 * With interrupts disabled, we block page table pages from being
-	 * freed from under us. See struct mmu_table_batch comments in
-	 * include/asm-generic/tlb.h for more details.
-	 *
-	 * We do not adopt an rcu_read_lock(.) here as we also want to
-	 * block IPIs that come from THPs splitting.
-	 */
-	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP) && gup_fast_permitted(start, end)) {
-		unsigned long fast_flags = gup_flags;
-
-		local_irq_save(flags);
-		gup_pgd_range(addr, end, fast_flags, pages, &nr_pinned);
-		local_irq_restore(flags);
-		ret = nr_pinned;
-	}
-
-	if (nr_pinned < nr_pages && !(gup_flags & FOLL_FAST_ONLY)) {
-		/* Try to get the remaining pages with get_user_pages */
-		start += nr_pinned << PAGE_SHIFT;
-		pages += nr_pinned;
+	nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
+	if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
+		return nr_pinned;
 
-		ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned,
-					      gup_flags, pages);
-
-		/* Have to be a bit careful with return values */
-		if (nr_pinned > 0) {
-			if (ret < 0)
-				ret = nr_pinned;
-			else
-				ret += nr_pinned;
-		}
+	/* Slow path: try to get the remaining pages with get_user_pages */
+	start += nr_pinned << PAGE_SHIFT;
+	pages += nr_pinned;
+	ret = __gup_longterm_unlocked(start, nr_pages - nr_pinned, gup_flags,
+				      pages);
+	if (ret < 0) {
+		/*
+		 * The caller has to unpin the pages we already pinned so
+		 * returning -errno is not an option
+		 */
+		if (nr_pinned)
+			return nr_pinned;
+		return ret;
 	}
-
-	return ret;
+	return ret + nr_pinned;
 }
+
 /**
  * get_user_pages_fast_only() - pin user pages in memory
  * @start:      starting user address