v4.19.13 snapshot.
diff --git a/mm/frame_vector.c b/mm/frame_vector.c
new file mode 100644
index 0000000..c64dca6
--- /dev/null
+++ b/mm/frame_vector.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/pagemap.h>
+#include <linux/sched.h>
+
+/**
+ * get_vaddr_frames() - map virtual addresses to pfns
+ * @start: starting user address
+ * @nr_frames: number of pages / pfns from start to map
+ * @gup_flags: flags modifying lookup behaviour
+ * @vec: structure which receives pages / pfns of the addresses mapped.
+ * It should have space for at least nr_frames entries.
+ *
+ * This function maps virtual addresses from @start and fills @vec structure
+ * with page frame numbers or page pointers to corresponding pages (choice
+ * depends on the type of the vma underlying the virtual address). If @start
+ * belongs to a normal vma, the function grabs reference to each of the pages
+ * to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
+ * touch page structures and the caller must make sure pfns aren't reused for
+ * anything else while he is using them.
+ *
+ * The function returns number of pages mapped which may be less than
+ * @nr_frames. In particular we stop mapping if there are more vmas of
+ * different type underlying the specified range of virtual addresses.
+ * When the function isn't able to map a single page, it returns error.
+ *
+ * This function takes care of grabbing mmap_sem as necessary.
+ */
+int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
+ unsigned int gup_flags, struct frame_vector *vec)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ int ret = 0;
+ int err;
+ int locked;
+
+ if (nr_frames == 0)
+ return 0;
+
+ if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
+ nr_frames = vec->nr_allocated;
+
+ down_read(&mm->mmap_sem);
+ locked = 1;
+ vma = find_vma_intersection(mm, start, start + 1);
+ if (!vma) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * While get_vaddr_frames() could be used for transient (kernel
+ * controlled lifetime) pinning of memory pages all current
+ * users establish long term (userspace controlled lifetime)
+ * page pinning. Treat get_vaddr_frames() like
+ * get_user_pages_longterm() and disallow it for filesystem-dax
+ * mappings.
+ */
+ if (vma_is_fsdax(vma)) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
+
+ if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
+ vec->got_ref = true;
+ vec->is_pfns = false;
+ ret = get_user_pages_locked(start, nr_frames,
+ gup_flags, (struct page **)(vec->ptrs), &locked);
+ goto out;
+ }
+
+ vec->got_ref = false;
+ vec->is_pfns = true;
+ do {
+ unsigned long *nums = frame_vector_pfns(vec);
+
+ while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
+ err = follow_pfn(vma, start, &nums[ret]);
+ if (err) {
+ if (ret == 0)
+ ret = err;
+ goto out;
+ }
+ start += PAGE_SIZE;
+ ret++;
+ }
+ /*
+ * We stop if we have enough pages or if VMA doesn't completely
+ * cover the tail page.
+ */
+ if (ret >= nr_frames || start < vma->vm_end)
+ break;
+ vma = find_vma_intersection(mm, start, start + 1);
+ } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
+out:
+ if (locked)
+ up_read(&mm->mmap_sem);
+ if (!ret)
+ ret = -EFAULT;
+ if (ret > 0)
+ vec->nr_frames = ret;
+ return ret;
+}
+EXPORT_SYMBOL(get_vaddr_frames);
+
+/**
+ * put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
+ * them
+ * @vec: frame vector to put
+ *
+ * Drop references to pages if get_vaddr_frames() acquired them. We also
+ * invalidate the frame vector so that it is prepared for the next call into
+ * get_vaddr_frames().
+ */
+void put_vaddr_frames(struct frame_vector *vec)
+{
+ int i;
+ struct page **pages;
+
+ if (!vec->got_ref)
+ goto out;
+ pages = frame_vector_pages(vec);
+ /*
+ * frame_vector_pages() might needed to do a conversion when
+ * get_vaddr_frames() got pages but vec was later converted to pfns.
+ * But it shouldn't really fail to convert pfns back...
+ */
+ if (WARN_ON(IS_ERR(pages)))
+ goto out;
+ for (i = 0; i < vec->nr_frames; i++)
+ put_page(pages[i]);
+ vec->got_ref = false;
+out:
+ vec->nr_frames = 0;
+}
+EXPORT_SYMBOL(put_vaddr_frames);
+
+/**
+ * frame_vector_to_pages - convert frame vector to contain page pointers
+ * @vec: frame vector to convert
+ *
+ * Convert @vec to contain array of page pointers. If the conversion is
+ * successful, return 0. Otherwise return an error. Note that we do not grab
+ * page references for the page structures.
+ */
+int frame_vector_to_pages(struct frame_vector *vec)
+{
+ int i;
+ unsigned long *nums;
+ struct page **pages;
+
+ if (!vec->is_pfns)
+ return 0;
+ nums = frame_vector_pfns(vec);
+ for (i = 0; i < vec->nr_frames; i++)
+ if (!pfn_valid(nums[i]))
+ return -EINVAL;
+ pages = (struct page **)nums;
+ for (i = 0; i < vec->nr_frames; i++)
+ pages[i] = pfn_to_page(nums[i]);
+ vec->is_pfns = false;
+ return 0;
+}
+EXPORT_SYMBOL(frame_vector_to_pages);
+
+/**
+ * frame_vector_to_pfns - convert frame vector to contain pfns
+ * @vec: frame vector to convert
+ *
+ * Convert @vec to contain array of pfns.
+ */
+void frame_vector_to_pfns(struct frame_vector *vec)
+{
+ int i;
+ unsigned long *nums;
+ struct page **pages;
+
+ if (vec->is_pfns)
+ return;
+ pages = (struct page **)(vec->ptrs);
+ nums = (unsigned long *)pages;
+ for (i = 0; i < vec->nr_frames; i++)
+ nums[i] = page_to_pfn(pages[i]);
+ vec->is_pfns = true;
+}
+EXPORT_SYMBOL(frame_vector_to_pfns);
+
+/**
+ * frame_vector_create() - allocate & initialize structure for pinned pfns
+ * @nr_frames: number of pfns slots we should reserve
+ *
+ * Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
+ * pfns.
+ */
+struct frame_vector *frame_vector_create(unsigned int nr_frames)
+{
+ struct frame_vector *vec;
+ int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
+
+ if (WARN_ON_ONCE(nr_frames == 0))
+ return NULL;
+ /*
+ * This is absurdly high. It's here just to avoid strange effects when
+ * arithmetics overflows.
+ */
+ if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
+ return NULL;
+ /*
+ * Avoid higher order allocations, use vmalloc instead. It should
+ * be rare anyway.
+ */
+ vec = kvmalloc(size, GFP_KERNEL);
+ if (!vec)
+ return NULL;
+ vec->nr_allocated = nr_frames;
+ vec->nr_frames = 0;
+ return vec;
+}
+EXPORT_SYMBOL(frame_vector_create);
+
+/**
+ * frame_vector_destroy() - free memory allocated to carry frame vector
+ * @vec: Frame vector to free
+ *
+ * Free structure allocated by frame_vector_create() to carry frames.
+ */
+void frame_vector_destroy(struct frame_vector *vec)
+{
+ /* Make sure put_vaddr_frames() got called properly... */
+ VM_BUG_ON(vec->nr_frames > 0);
+ kvfree(vec);
+}
+EXPORT_SYMBOL(frame_vector_destroy);