Linux 4.20.17

[thirdparty/kernel/stable.git] / mm / gup.c

diff --git a/mm/gup.c b/mm/gup.c
index f76e77a2d34b79afec5f3032366a6bd954d1aead..8cb68a50dbdf28a27dfaef6dce27e6cdb1f87881 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -385,11 +385,17 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
  * @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
+ * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a
+ *       pointer to output page_mask
  *
  * @flags can have FOLL_ flags set, defined in <linux/mm.h>
  *
- * Returns the mapped (struct page *), %NULL if no mapping exists, or
+ * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches
+ * the device's dev_pagemap metadata to avoid repeating expensive lookups.
+ *
+ * On output, the @ctx->page_mask is set according to the size of the page.
+ *
+ * Return: 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()).
  */
@@ -696,12 +702,11 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                if (!vma || start >= vma->vm_end) {
                        vma = find_extend_vma(mm, start);
                        if (!vma && in_gate_area(mm, start)) {
-                               int ret;
                                ret = get_gate_page(mm, start & PAGE_MASK,
                                                gup_flags, &vma,
                                                pages ? &pages[i] : NULL);
                                if (ret)
-                                       return i ? : ret;
+                                       goto out;
                                ctx.page_mask = 0;
                                goto next_page;
                        }