Merge branch 'next' (accumulated 3.16 merge window patches) into master

Now that 3.15 is released, this merges the 'next' branch into 'master',
bringing us to the normal situation where my 'master' branch is the
merge window.

* accumulated work in next: (6809 commits)
  ufs: sb mutex merge + mutex_destroy
  powerpc: update comments for generic idle conversion
  cris: update comments for generic idle conversion
  idle: remove cpu_idle() forward declarations
  nbd: zero from and len fields in NBD_CMD_DISCONNECT.
  mm: convert some level-less printks to pr_*
  MAINTAINERS: adi-buildroot-devel is moderated
  MAINTAINERS: add linux-api for review of API/ABI changes
  mm/kmemleak-test.c: use pr_fmt for logging
  fs/dlm/debug_fs.c: replace seq_printf by seq_puts
  fs/dlm/lockspace.c: convert simple_str to kstr
  fs/dlm/config.c: convert simple_str to kstr
  mm: mark remap_file_pages() syscall as deprecated
  mm: memcontrol: remove unnecessary memcg argument from soft limit functions
  mm: memcontrol: clean up memcg zoneinfo lookup
  mm/memblock.c: call kmemleak directly from memblock_(alloc|free)
  mm/mempool.c: update the kmemleak stack trace for mempool allocations
  lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations
  mm: introduce kmemleak_update_trace()
  mm/kmemleak.c: use %u to print ->checksum
  ...

1 files changed, 55 insertions, 691 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 037b812a9531..d67fd9fcf1f2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -698,11 +698,6 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
-static inline bool is_cow_mapping(vm_flags_t flags)
-{
-	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
-}
-
 /*
  * vm_normal_page -- This function gets the "struct page" associated with a pte.
  *
@@ -756,7 +751,7 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 	unsigned long pfn = pte_pfn(pte);
 
 	if (HAVE_PTE_SPECIAL) {
-		if (likely(!pte_special(pte)))
+		if (likely(!pte_special(pte) || pte_numa(pte)))
 			goto check_pfn;
 		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
 			return NULL;
@@ -782,14 +777,15 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 		}
 	}
 
-	if (is_zero_pfn(pfn))
-		return NULL;
 check_pfn:
 	if (unlikely(pfn > highest_memmap_pfn)) {
 		print_bad_pte(vma, addr, pte, NULL);
 		return NULL;
 	}
 
+	if (is_zero_pfn(pfn))
+		return NULL;
+
 	/*
 	 * NOTE! We still have PageReserved() pages in the page tables.
 	 * eg. VDSO mappings can cause them to exist.
@@ -1457,646 +1453,6 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
-/**
- * follow_page_mask - look up a page descriptor from a user-virtual address
- * @vma: vm_area_struct mapping @address
- * @address: virtual address to look up
- * @flags: flags modifying lookup behaviour
- * @page_mask: on output, *page_mask is set according to the size of the page
- *
- * @flags can have FOLL_ flags set, defined in <linux/mm.h>
- *
- * Returns the mapped (struct page *), %NULL if no mapping exists, or
- * an error pointer if there is a mapping to something not represented
- * by a page descriptor (see also vm_normal_page()).
- */
-struct page *follow_page_mask(struct vm_area_struct *vma,
-			      unsigned long address, unsigned int flags,
-			      unsigned int *page_mask)
-{
-	pgd_t *pgd;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *ptep, pte;
-	spinlock_t *ptl;
-	struct page *page;
-	struct mm_struct *mm = vma->vm_mm;
-
-	*page_mask = 0;
-
-	page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
-	if (!IS_ERR(page)) {
-		BUG_ON(flags & FOLL_GET);
-		goto out;
-	}
-
-	page = NULL;
-	pgd = pgd_offset(mm, address);
-	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
-		goto no_page_table;
-
-	pud = pud_offset(pgd, address);
-	if (pud_none(*pud))
-		goto no_page_table;
-	if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
-		if (flags & FOLL_GET)
-			goto out;
-		page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
-		goto out;
-	}
-	if (unlikely(pud_bad(*pud)))
-		goto no_page_table;
-
-	pmd = pmd_offset(pud, address);
-	if (pmd_none(*pmd))
-		goto no_page_table;
-	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
-		page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
-		if (flags & FOLL_GET) {
-			/*
-			 * Refcount on tail pages are not well-defined and
-			 * shouldn't be taken. The caller should handle a NULL
-			 * return when trying to follow tail pages.
-			 */
-			if (PageHead(page))
-				get_page(page);
-			else {
-				page = NULL;
-				goto out;
-			}
-		}
-		goto out;
-	}
-	if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
-		goto no_page_table;
-	if (pmd_trans_huge(*pmd)) {
-		if (flags & FOLL_SPLIT) {
-			split_huge_page_pmd(vma, address, pmd);
-			goto split_fallthrough;
-		}
-		ptl = pmd_lock(mm, pmd);
-		if (likely(pmd_trans_huge(*pmd))) {
-			if (unlikely(pmd_trans_splitting(*pmd))) {
-				spin_unlock(ptl);
-				wait_split_huge_page(vma->anon_vma, pmd);
-			} else {
-				page = follow_trans_huge_pmd(vma, address,
-							     pmd, flags);
-				spin_unlock(ptl);
-				*page_mask = HPAGE_PMD_NR - 1;
-				goto out;
-			}
-		} else
-			spin_unlock(ptl);
-		/* fall through */
-	}
-split_fallthrough:
-	if (unlikely(pmd_bad(*pmd)))
-		goto no_page_table;
-
-	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
-
-	pte = *ptep;
-	if (!pte_present(pte)) {
-		swp_entry_t entry;
-		/*
-		 * KSM's break_ksm() relies upon recognizing a ksm page
-		 * even while it is being migrated, so for that case we
-		 * need migration_entry_wait().
-		 */
-		if (likely(!(flags & FOLL_MIGRATION)))
-			goto no_page;
-		if (pte_none(pte) || pte_file(pte))
-			goto no_page;
-		entry = pte_to_swp_entry(pte);
-		if (!is_migration_entry(entry))
-			goto no_page;
-		pte_unmap_unlock(ptep, ptl);
-		migration_entry_wait(mm, pmd, address);
-		goto split_fallthrough;
-	}
-	if ((flags & FOLL_NUMA) && pte_numa(pte))
-		goto no_page;
-	if ((flags & FOLL_WRITE) && !pte_write(pte))
-		goto unlock;
-
-	page = vm_normal_page(vma, address, pte);
-	if (unlikely(!page)) {
-		if ((flags & FOLL_DUMP) ||
-		    !is_zero_pfn(pte_pfn(pte)))
-			goto bad_page;
-		page = pte_page(pte);
-	}
-
-	if (flags & FOLL_GET)
-		get_page_foll(page);
-	if (flags & FOLL_TOUCH) {
-		if ((flags & FOLL_WRITE) &&
-		    !pte_dirty(pte) && !PageDirty(page))
-			set_page_dirty(page);
-		/*
-		 * pte_mkyoung() would be more correct here, but atomic care
-		 * is needed to avoid losing the dirty bit: it is easier to use
-		 * mark_page_accessed().
-		 */
-		mark_page_accessed(page);
-	}
-	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
-		/*
-		 * The preliminary mapping check is mainly to avoid the
-		 * pointless overhead of lock_page on the ZERO_PAGE
-		 * which might bounce very badly if there is contention.
-		 *
-		 * If the page is already locked, we don't need to
-		 * handle it now - vmscan will handle it later if and
-		 * when it attempts to reclaim the page.
-		 */
-		if (page->mapping && trylock_page(page)) {
-			lru_add_drain();  /* push cached pages to LRU */
-			/*
-			 * Because we lock page here, and migration is
-			 * blocked by the pte's page reference, and we
-			 * know the page is still mapped, we don't even
-			 * need to check for file-cache page truncation.
-			 */
-			mlock_vma_page(page);
-			unlock_page(page);
-		}
-	}
-unlock:
-	pte_unmap_unlock(ptep, ptl);
-out:
-	return page;
-
-bad_page:
-	pte_unmap_unlock(ptep, ptl);
-	return ERR_PTR(-EFAULT);
-
-no_page:
-	pte_unmap_unlock(ptep, ptl);
-	if (!pte_none(pte))
-		return page;
-
-no_page_table:
-	/*
-	 * When core dumping an enormous anonymous area that nobody
-	 * has touched so far, we don't want to allocate unnecessary pages or
-	 * page tables.  Return error instead of NULL to skip handle_mm_fault,
-	 * then get_dump_page() will return NULL to leave a hole in the dump.
-	 * But we can only make this optimization where a hole would surely
-	 * be zero-filled if handle_mm_fault() actually did handle it.
-	 */
-	if ((flags & FOLL_DUMP) &&
-	    (!vma->vm_ops || !vma->vm_ops->fault))
-		return ERR_PTR(-EFAULT);
-	return page;
-}
-
-static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
-{
-	return stack_guard_page_start(vma, addr) ||
-	       stack_guard_page_end(vma, addr+PAGE_SIZE);
-}
-
-/**
- * __get_user_pages() - pin user pages in memory
- * @tsk:	task_struct of target task
- * @mm:		mm_struct of target mm
- * @start:	starting user address
- * @nr_pages:	number of pages from start to pin
- * @gup_flags:	flags modifying pin 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.
- * @vmas:	array of pointers to vmas corresponding to each page.
- *		Or NULL if the caller does not require them.
- * @nonblocking: whether waiting for disk IO or mmap_sem contention
- *
- * Returns number of pages pinned. This may be fewer than the number
- * requested. If nr_pages is 0 or negative, returns 0. If no pages
- * were pinned, returns -errno. Each page returned must be released
- * with a put_page() call when it is finished with. vmas will only
- * remain valid while mmap_sem is held.
- *
- * Must be called with mmap_sem held for read or write.
- *
- * __get_user_pages walks a process's page tables and takes a reference to
- * each struct page that each user address corresponds to at a given
- * instant. That is, it takes the page that would be accessed if a user
- * thread accesses the given user virtual address at that instant.
- *
- * This does not guarantee that the page exists in the user mappings when
- * __get_user_pages returns, and there may even be a completely different
- * page there in some cases (eg. if mmapped pagecache has been invalidated
- * and subsequently re faulted). However it does guarantee that the page
- * won't be freed completely. And mostly callers simply care that the page
- * contains data that was valid *at some point in time*. Typically, an IO
- * or similar operation cannot guarantee anything stronger anyway because
- * locks can't be held over the syscall boundary.
- *
- * If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
- * the page is written to, set_page_dirty (or set_page_dirty_lock, as
- * appropriate) must be called after the page is finished with, and
- * before put_page is called.
- *
- * If @nonblocking != NULL, __get_user_pages will not wait for disk IO
- * or mmap_sem contention, and if waiting is needed to pin all pages,
- * *@nonblocking will be set to 0.
- *
- * In most cases, get_user_pages or get_user_pages_fast should be used
- * instead of __get_user_pages. __get_user_pages should be used only if
- * you need some special @gup_flags.
- */
-long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-		unsigned long start, unsigned long nr_pages,
-		unsigned int gup_flags, struct page **pages,
-		struct vm_area_struct **vmas, int *nonblocking)
-{
-	long i;
-	unsigned long vm_flags;
-	unsigned int page_mask;
-
-	if (!nr_pages)
-		return 0;
-
-	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
-
-	/*
-	 * If FOLL_FORCE and FOLL_NUMA are both set, handle_mm_fault
-	 * would be called on PROT_NONE ranges. We must never invoke
-	 * handle_mm_fault on PROT_NONE ranges or the NUMA hinting
-	 * page faults would unprotect the PROT_NONE ranges if
-	 * _PAGE_NUMA and _PAGE_PROTNONE are sharing the same pte/pmd
-	 * bitflag. So to avoid that, don't set FOLL_NUMA if
-	 * FOLL_FORCE is set.
-	 */
-	if (!(gup_flags & FOLL_FORCE))
-		gup_flags |= FOLL_NUMA;
-
-	i = 0;
-
-	do {
-		struct vm_area_struct *vma;
-
-		vma = find_extend_vma(mm, start);
-		if (!vma && in_gate_area(mm, start)) {
-			unsigned long pg = start & PAGE_MASK;
-			pgd_t *pgd;
-			pud_t *pud;
-			pmd_t *pmd;
-			pte_t *pte;
-
-			/* user gate pages are read-only */
-			if (gup_flags & FOLL_WRITE)
-				goto efault;
-			if (pg > TASK_SIZE)
-				pgd = pgd_offset_k(pg);
-			else
-				pgd = pgd_offset_gate(mm, pg);
-			BUG_ON(pgd_none(*pgd));
-			pud = pud_offset(pgd, pg);
-			BUG_ON(pud_none(*pud));
-			pmd = pmd_offset(pud, pg);
-			if (pmd_none(*pmd))
-				goto efault;
-			VM_BUG_ON(pmd_trans_huge(*pmd));
-			pte = pte_offset_map(pmd, pg);
-			if (pte_none(*pte)) {
-				pte_unmap(pte);
-				goto efault;
-			}
-			vma = get_gate_vma(mm);
-			if (pages) {
-				struct page *page;
-
-				page = vm_normal_page(vma, start, *pte);
-				if (!page) {
-					if (!(gup_flags & FOLL_DUMP) &&
-					     is_zero_pfn(pte_pfn(*pte)))
-						page = pte_page(*pte);
-					else {
-						pte_unmap(pte);
-						goto efault;
-					}
-				}
-				pages[i] = page;
-				get_page(page);
-			}
-			pte_unmap(pte);
-			page_mask = 0;
-			goto next_page;
-		}
-
-		if (!vma)
-			goto efault;
-		vm_flags = vma->vm_flags;
-		if (vm_flags & (VM_IO | VM_PFNMAP))
-			goto efault;
-
-		if (gup_flags & FOLL_WRITE) {
-			if (!(vm_flags & VM_WRITE)) {
-				if (!(gup_flags & FOLL_FORCE))
-					goto efault;
-				/*
-				 * We used to let the write,force case do COW
-				 * in a VM_MAYWRITE VM_SHARED !VM_WRITE vma, so
-				 * ptrace could set a breakpoint in a read-only
-				 * mapping of an executable, without corrupting
-				 * the file (yet only when that file had been
-				 * opened for writing!).  Anon pages in shared
-				 * mappings are surprising: now just reject it.
-				 */
-				if (!is_cow_mapping(vm_flags)) {
-					WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
-					goto efault;
-				}
-			}
-		} else {
-			if (!(vm_flags & VM_READ)) {
-				if (!(gup_flags & FOLL_FORCE))
-					goto efault;
-				/*
-				 * Is there actually any vma we can reach here
-				 * which does not have VM_MAYREAD set?
-				 */
-				if (!(vm_flags & VM_MAYREAD))
-					goto efault;
-			}
-		}
-
-		if (is_vm_hugetlb_page(vma)) {
-			i = follow_hugetlb_page(mm, vma, pages, vmas,
-					&start, &nr_pages, i, gup_flags);
-			continue;
-		}
-
-		do {
-			struct page *page;
-			unsigned int foll_flags = gup_flags;
-			unsigned int page_increm;
-
-			/*
-			 * If we have a pending SIGKILL, don't keep faulting
-			 * pages and potentially allocating memory.
-			 */
-			if (unlikely(fatal_signal_pending(current)))
-				return i ? i : -ERESTARTSYS;
-
-			cond_resched();
-			while (!(page = follow_page_mask(vma, start,
-						foll_flags, &page_mask))) {
-				int ret;
-				unsigned int fault_flags = 0;
-
-				/* For mlock, just skip the stack guard page. */
-				if (foll_flags & FOLL_MLOCK) {
-					if (stack_guard_page(vma, start))
-						goto next_page;
-				}
-				if (foll_flags & FOLL_WRITE)
-					fault_flags |= FAULT_FLAG_WRITE;
-				if (nonblocking)
-					fault_flags |= FAULT_FLAG_ALLOW_RETRY;
-				if (foll_flags & FOLL_NOWAIT)
-					fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
-
-				ret = handle_mm_fault(mm, vma, start,
-							fault_flags);
-
-				if (ret & VM_FAULT_ERROR) {
-					if (ret & VM_FAULT_OOM)
-						return i ? i : -ENOMEM;
-					if (ret & (VM_FAULT_HWPOISON |
-						   VM_FAULT_HWPOISON_LARGE)) {
-						if (i)
-							return i;
-						else if (gup_flags & FOLL_HWPOISON)
-							return -EHWPOISON;
-						else
-							return -EFAULT;
-					}
-					if (ret & VM_FAULT_SIGBUS)
-						goto efault;
-					BUG();
-				}
-
-				if (tsk) {
-					if (ret & VM_FAULT_MAJOR)
-						tsk->maj_flt++;
-					else
-						tsk->min_flt++;
-				}
-
-				if (ret & VM_FAULT_RETRY) {
-					if (nonblocking)
-						*nonblocking = 0;
-					return i;
-				}
-
-				/*
-				 * The VM_FAULT_WRITE bit tells us that
-				 * do_wp_page has broken COW when necessary,
-				 * even if maybe_mkwrite decided not to set
-				 * pte_write. We can thus safely do subsequent
-				 * page lookups as if they were reads. But only
-				 * do so when looping for pte_write is futile:
-				 * in some cases userspace may also be wanting
-				 * to write to the gotten user page, which a
-				 * read fault here might prevent (a readonly
-				 * page might get reCOWed by userspace write).
-				 */
-				if ((ret & VM_FAULT_WRITE) &&
-				    !(vma->vm_flags & VM_WRITE))
-					foll_flags &= ~FOLL_WRITE;
-
-				cond_resched();
-			}
-			if (IS_ERR(page))
-				return i ? i : PTR_ERR(page);
-			if (pages) {
-				pages[i] = page;
-
-				flush_anon_page(vma, page, start);
-				flush_dcache_page(page);
-				page_mask = 0;
-			}
-next_page:
-			if (vmas) {
-				vmas[i] = vma;
-				page_mask = 0;
-			}
-			page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
-			if (page_increm > nr_pages)
-				page_increm = nr_pages;
-			i += page_increm;
-			start += page_increm * PAGE_SIZE;
-			nr_pages -= page_increm;
-		} while (nr_pages && start < vma->vm_end);
-	} while (nr_pages);
-	return i;
-efault:
-	return i ? : -EFAULT;
-}
-EXPORT_SYMBOL(__get_user_pages);
-
-/*
- * fixup_user_fault() - manually resolve a user page fault
- * @tsk:	the task_struct to use for page fault accounting, or
- *		NULL if faults are not to be recorded.
- * @mm:		mm_struct of target mm
- * @address:	user address
- * @fault_flags:flags to pass down to handle_mm_fault()
- *
- * This is meant to be called in the specific scenario where for locking reasons
- * we try to access user memory in atomic context (within a pagefault_disable()
- * section), this returns -EFAULT, and we want to resolve the user fault before
- * trying again.
- *
- * Typically this is meant to be used by the futex code.
- *
- * The main difference with get_user_pages() is that this function will
- * unconditionally call handle_mm_fault() which will in turn perform all the
- * necessary SW fixup of the dirty and young bits in the PTE, while
- * handle_mm_fault() only guarantees to update these in the struct page.
- *
- * This is important for some architectures where those bits also gate the
- * access permission to the page because they are maintained in software.  On
- * such architectures, gup() will not be enough to make a subsequent access
- * succeed.
- *
- * This should be called with the mm_sem held for read.
- */
-int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
-		     unsigned long address, unsigned int fault_flags)
-{
-	struct vm_area_struct *vma;
-	vm_flags_t vm_flags;
-	int ret;
-
-	vma = find_extend_vma(mm, address);
-	if (!vma || address < vma->vm_start)
-		return -EFAULT;
-
-	vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
-	if (!(vm_flags & vma->vm_flags))
-		return -EFAULT;
-
-	ret = handle_mm_fault(mm, vma, address, fault_flags);
-	if (ret & VM_FAULT_ERROR) {
-		if (ret & VM_FAULT_OOM)
-			return -ENOMEM;
-		if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
-			return -EHWPOISON;
-		if (ret & VM_FAULT_SIGBUS)
-			return -EFAULT;
-		BUG();
-	}
-	if (tsk) {
-		if (ret & VM_FAULT_MAJOR)
-			tsk->maj_flt++;
-		else
-			tsk->min_flt++;
-	}
-	return 0;
-}
-
-/*
- * get_user_pages() - pin user pages in memory
- * @tsk:	the task_struct to use for page fault accounting, or
- *		NULL if faults are not to be recorded.
- * @mm:		mm_struct of target mm
- * @start:	starting user address
- * @nr_pages:	number of pages from start to pin
- * @write:	whether pages will be written to by the caller
- * @force:	whether to force access even when user mapping is currently
- *		protected (but never forces write access to shared mapping).
- * @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.
- * @vmas:	array of pointers to vmas corresponding to each page.
- *		Or NULL if the caller does not require them.
- *
- * Returns number of pages pinned. This may be fewer than the number
- * requested. If nr_pages is 0 or negative, returns 0. If no pages
- * were pinned, returns -errno. Each page returned must be released
- * with a put_page() call when it is finished with. vmas will only
- * remain valid while mmap_sem is held.
- *
- * Must be called with mmap_sem held for read or write.
- *
- * get_user_pages walks a process's page tables and takes a reference to
- * each struct page that each user address corresponds to at a given
- * instant. That is, it takes the page that would be accessed if a user
- * thread accesses the given user virtual address at that instant.
- *
- * This does not guarantee that the page exists in the user mappings when
- * get_user_pages returns, and there may even be a completely different
- * page there in some cases (eg. if mmapped pagecache has been invalidated
- * and subsequently re faulted). However it does guarantee that the page
- * won't be freed completely. And mostly callers simply care that the page
- * contains data that was valid *at some point in time*. Typically, an IO
- * or similar operation cannot guarantee anything stronger anyway because
- * locks can't be held over the syscall boundary.
- *
- * If write=0, the page must not be written to. If the page is written to,
- * set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
- * after the page is finished with, and before put_page is called.
- *
- * get_user_pages is typically used for fewer-copy IO operations, to get a
- * handle on the memory by some means other than accesses via the user virtual
- * addresses. The pages may be submitted for DMA to devices or accessed via
- * their kernel linear mapping (via the kmap APIs). Care should be taken to
- * use the correct cache flushing APIs.
- *
- * See also get_user_pages_fast, for performance critical applications.
- */
-long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-		unsigned long start, unsigned long nr_pages, int write,
-		int force, struct page **pages, struct vm_area_struct **vmas)
-{
-	int flags = FOLL_TOUCH;
-
-	if (pages)
-		flags |= FOLL_GET;
-	if (write)
-		flags |= FOLL_WRITE;
-	if (force)
-		flags |= FOLL_FORCE;
-
-	return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
-				NULL);
-}
-EXPORT_SYMBOL(get_user_pages);
-
-/**
- * get_dump_page() - pin user page in memory while writing it to core dump
- * @addr: user address
- *
- * Returns struct page pointer of user page pinned for dump,
- * to be freed afterwards by page_cache_release() or put_page().
- *
- * Returns NULL on any kind of failure - a hole must then be inserted into
- * the corefile, to preserve alignment with its headers; and also returns
- * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
- * allowing a hole to be left in the corefile to save diskspace.
- *
- * Called without mmap_sem, but after all other threads have been killed.
- */
-#ifdef CONFIG_ELF_CORE
-struct page *get_dump_page(unsigned long addr)
-{
-	struct vm_area_struct *vma;
-	struct page *page;
-
-	if (__get_user_pages(current, current->mm, addr, 1,
-			     FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
-			     NULL) < 1)
-		return NULL;
-	flush_cache_page(vma, addr, page_to_pfn(page));
-	return page;
-}
-#endif /* CONFIG_ELF_CORE */
-
 pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
 			spinlock_t **ptl)
 {
@@ -3402,65 +2758,76 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
 	update_mmu_cache(vma, address, pte);
 }
 
-#define FAULT_AROUND_ORDER 4
+static unsigned long fault_around_bytes = 65536;
 
-#ifdef CONFIG_DEBUG_FS
-static unsigned int fault_around_order = FAULT_AROUND_ORDER;
+/*
+ * fault_around_pages() and fault_around_mask() round down fault_around_bytes
+ * to nearest page order. It's what do_fault_around() expects to see.
+ */
+static inline unsigned long fault_around_pages(void)
+{
+	return rounddown_pow_of_two(fault_around_bytes) / PAGE_SIZE;
+}
+
+static inline unsigned long fault_around_mask(void)
+{
+	return ~(rounddown_pow_of_two(fault_around_bytes) - 1) & PAGE_MASK;
+}
 
-static int fault_around_order_get(void *data, u64 *val)
+
+#ifdef CONFIG_DEBUG_FS
+static int fault_around_bytes_get(void *data, u64 *val)
 {
-	*val = fault_around_order;
+	*val = fault_around_bytes;
 	return 0;
 }
 
-static int fault_around_order_set(void *data, u64 val)
+static int fault_around_bytes_set(void *data, u64 val)
 {
-	BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
-	if (1UL << val > PTRS_PER_PTE)
+	if (val / PAGE_SIZE > PTRS_PER_PTE)
 		return -EINVAL;
-	fault_around_order = val;
+	fault_around_bytes = val;
 	return 0;
 }
-DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,
-		fault_around_order_get, fault_around_order_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
+		fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
 
 static int __init fault_around_debugfs(void)
 {
 	void *ret;
 
-	ret = debugfs_create_file("fault_around_order",	0644, NULL, NULL,
-			&fault_around_order_fops);
+	ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
+			&fault_around_bytes_fops);
 	if (!ret)
-		pr_warn("Failed to create fault_around_order in debugfs");
+		pr_warn("Failed to create fault_around_bytes in debugfs");
 	return 0;
 }
 late_initcall(fault_around_debugfs);
-
-static inline unsigned long fault_around_pages(void)
-{
-	return 1UL << fault_around_order;
-}
-
-static inline unsigned long fault_around_mask(void)
-{
-	return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);
-}
-#else
-static inline unsigned long fault_around_pages(void)
-{
-	unsigned long nr_pages;
-
-	nr_pages = 1UL << FAULT_AROUND_ORDER;
-	BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);
-	return nr_pages;
-}
-
-static inline unsigned long fault_around_mask(void)
-{
-	return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);
-}
 #endif
 
+/*
+ * do_fault_around() tries to map few pages around the fault address. The hope
+ * is that the pages will be needed soon and this will lower the number of
+ * faults to handle.
+ *
+ * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
+ * not ready to be mapped: not up-to-date, locked, etc.
+ *
+ * This function is called with the page table lock taken. In the split ptlock
+ * case the page table lock only protects only those entries which belong to
+ * the page table corresponding to the fault address.
+ *
+ * This function doesn't cross the VMA boundaries, in order to call map_pages()
+ * only once.
+ *
+ * fault_around_pages() defines how many pages we'll try to map.
+ * do_fault_around() expects it to return a power of two less than or equal to
+ * PTRS_PER_PTE.
+ *
+ * The virtual address of the area that we map is naturally aligned to the
+ * fault_around_pages() value (and therefore to page order).  This way it's
+ * easier to guarantee that we don't cross page table boundaries.
+ */
 static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
 		pte_t *pte, pgoff_t pgoff, unsigned int flags)
 {
@@ -3476,7 +2843,7 @@ static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
 
 	/*
 	 *  max_pgoff is either end of page table or end of vma
-	 *  or fault_around_pages() from pgoff, depending what is neast.
+	 *  or fault_around_pages() from pgoff, depending what is nearest.
 	 */
 	max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
 		PTRS_PER_PTE - 1;
@@ -3515,7 +2882,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * if page by the offset is not ready to be mapped (cold cache or
 	 * something).
 	 */
-	if (vma->vm_ops->map_pages) {
+	if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
 		pte = pte_offset_map_lock(mm, pmd, address, &ptl);
 		do_fault_around(vma, address, pte, pgoff, flags);
 		if (!pte_same(*pte, orig_pte))
@@ -3920,9 +3287,6 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		}
 	}
 
-	/* THP should already have been handled */
-	BUG_ON(pmd_numa(*pmd));
-
 	/*
 	 * Use __pte_alloc instead of pte_alloc_map, because we can't
 	 * run pte_offset_map on the pmd, if an huge pmd could