v4.19.13 snapshot.
diff --git a/mm/mincore.c b/mm/mincore.c
new file mode 100644
index 0000000..fc37afe
--- /dev/null
+++ b/mm/mincore.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/mm/mincore.c
+ *
+ * Copyright (C) 1994-2006 Linus Torvalds
+ */
+
+/*
+ * The mincore() system call.
+ */
+#include <linux/pagemap.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/syscalls.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/shmem_fs.h>
+#include <linux/hugetlb.h>
+
+#include <linux/uaccess.h>
+#include <asm/pgtable.h>
+
+static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
+ unsigned long end, struct mm_walk *walk)
+{
+#ifdef CONFIG_HUGETLB_PAGE
+ unsigned char present;
+ unsigned char *vec = walk->private;
+
+ /*
+ * Hugepages under user process are always in RAM and never
+ * swapped out, but theoretically it needs to be checked.
+ */
+ present = pte && !huge_pte_none(huge_ptep_get(pte));
+ for (; addr != end; vec++, addr += PAGE_SIZE)
+ *vec = present;
+ walk->private = vec;
+#else
+ BUG();
+#endif
+ return 0;
+}
+
+/*
+ * Later we can get more picky about what "in core" means precisely.
+ * For now, simply check to see if the page is in the page cache,
+ * and is up to date; i.e. that no page-in operation would be required
+ * at this time if an application were to map and access this page.
+ */
+static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
+{
+ unsigned char present = 0;
+ struct page *page;
+
+ /*
+ * When tmpfs swaps out a page from a file, any process mapping that
+ * file will not get a swp_entry_t in its pte, but rather it is like
+ * any other file mapping (ie. marked !present and faulted in with
+ * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
+ */
+#ifdef CONFIG_SWAP
+ if (shmem_mapping(mapping)) {
+ page = find_get_entry(mapping, pgoff);
+ /*
+ * shmem/tmpfs may return swap: account for swapcache
+ * page too.
+ */
+ if (radix_tree_exceptional_entry(page)) {
+ swp_entry_t swp = radix_to_swp_entry(page);
+ page = find_get_page(swap_address_space(swp),
+ swp_offset(swp));
+ }
+ } else
+ page = find_get_page(mapping, pgoff);
+#else
+ page = find_get_page(mapping, pgoff);
+#endif
+ if (page) {
+ present = PageUptodate(page);
+ put_page(page);
+ }
+
+ return present;
+}
+
+static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
+ struct vm_area_struct *vma, unsigned char *vec)
+{
+ unsigned long nr = (end - addr) >> PAGE_SHIFT;
+ int i;
+
+ if (vma->vm_file) {
+ pgoff_t pgoff;
+
+ pgoff = linear_page_index(vma, addr);
+ for (i = 0; i < nr; i++, pgoff++)
+ vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
+ } else {
+ for (i = 0; i < nr; i++)
+ vec[i] = 0;
+ }
+ return nr;
+}
+
+static int mincore_unmapped_range(unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
+{
+ walk->private += __mincore_unmapped_range(addr, end,
+ walk->vma, walk->private);
+ return 0;
+}
+
+static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
+{
+ spinlock_t *ptl;
+ struct vm_area_struct *vma = walk->vma;
+ pte_t *ptep;
+ unsigned char *vec = walk->private;
+ int nr = (end - addr) >> PAGE_SHIFT;
+
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (ptl) {
+ memset(vec, 1, nr);
+ spin_unlock(ptl);
+ goto out;
+ }
+
+ if (pmd_trans_unstable(pmd)) {
+ __mincore_unmapped_range(addr, end, vma, vec);
+ goto out;
+ }
+
+ ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ for (; addr != end; ptep++, addr += PAGE_SIZE) {
+ pte_t pte = *ptep;
+
+ if (pte_none(pte))
+ __mincore_unmapped_range(addr, addr + PAGE_SIZE,
+ vma, vec);
+ else if (pte_present(pte))
+ *vec = 1;
+ else { /* pte is a swap entry */
+ swp_entry_t entry = pte_to_swp_entry(pte);
+
+ if (non_swap_entry(entry)) {
+ /*
+ * migration or hwpoison entries are always
+ * uptodate
+ */
+ *vec = 1;
+ } else {
+#ifdef CONFIG_SWAP
+ *vec = mincore_page(swap_address_space(entry),
+ swp_offset(entry));
+#else
+ WARN_ON(1);
+ *vec = 1;
+#endif
+ }
+ }
+ vec++;
+ }
+ pte_unmap_unlock(ptep - 1, ptl);
+out:
+ walk->private += nr;
+ cond_resched();
+ return 0;
+}
+
+/*
+ * Do a chunk of "sys_mincore()". We've already checked
+ * all the arguments, we hold the mmap semaphore: we should
+ * just return the amount of info we're asked for.
+ */
+static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
+{
+ struct vm_area_struct *vma;
+ unsigned long end;
+ int err;
+ struct mm_walk mincore_walk = {
+ .pmd_entry = mincore_pte_range,
+ .pte_hole = mincore_unmapped_range,
+ .hugetlb_entry = mincore_hugetlb,
+ .private = vec,
+ };
+
+ vma = find_vma(current->mm, addr);
+ if (!vma || addr < vma->vm_start)
+ return -ENOMEM;
+ mincore_walk.mm = vma->vm_mm;
+ end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
+ err = walk_page_range(addr, end, &mincore_walk);
+ if (err < 0)
+ return err;
+ return (end - addr) >> PAGE_SHIFT;
+}
+
+/*
+ * The mincore(2) system call.
+ *
+ * mincore() returns the memory residency status of the pages in the
+ * current process's address space specified by [addr, addr + len).
+ * The status is returned in a vector of bytes. The least significant
+ * bit of each byte is 1 if the referenced page is in memory, otherwise
+ * it is zero.
+ *
+ * Because the status of a page can change after mincore() checks it
+ * but before it returns to the application, the returned vector may
+ * contain stale information. Only locked pages are guaranteed to
+ * remain in memory.
+ *
+ * return values:
+ * zero - success
+ * -EFAULT - vec points to an illegal address
+ * -EINVAL - addr is not a multiple of PAGE_SIZE
+ * -ENOMEM - Addresses in the range [addr, addr + len] are
+ * invalid for the address space of this process, or
+ * specify one or more pages which are not currently
+ * mapped
+ * -EAGAIN - A kernel resource was temporarily unavailable.
+ */
+SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
+ unsigned char __user *, vec)
+{
+ long retval;
+ unsigned long pages;
+ unsigned char *tmp;
+
+ /* Check the start address: needs to be page-aligned.. */
+ if (start & ~PAGE_MASK)
+ return -EINVAL;
+
+ /* ..and we need to be passed a valid user-space range */
+ if (!access_ok(VERIFY_READ, (void __user *) start, len))
+ return -ENOMEM;
+
+ /* This also avoids any overflows on PAGE_ALIGN */
+ pages = len >> PAGE_SHIFT;
+ pages += (offset_in_page(len)) != 0;
+
+ if (!access_ok(VERIFY_WRITE, vec, pages))
+ return -EFAULT;
+
+ tmp = (void *) __get_free_page(GFP_USER);
+ if (!tmp)
+ return -EAGAIN;
+
+ retval = 0;
+ while (pages) {
+ /*
+ * Do at most PAGE_SIZE entries per iteration, due to
+ * the temporary buffer size.
+ */
+ down_read(¤t->mm->mmap_sem);
+ retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
+ up_read(¤t->mm->mmap_sem);
+
+ if (retval <= 0)
+ break;
+ if (copy_to_user(vec, tmp, retval)) {
+ retval = -EFAULT;
+ break;
+ }
+ pages -= retval;
+ vec += retval;
+ start += retval << PAGE_SHIFT;
+ retval = 0;
+ }
+ free_page((unsigned long) tmp);
+ return retval;
+}