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-rw-r--r--mm/gup.c58
1 files changed, 58 insertions, 0 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 8651309f8ec3..728d996767cb 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1501,6 +1501,64 @@ long populate_vma_page_range(struct vm_area_struct *vma,
}
/*
+ * faultin_vma_page_range() - populate (prefault) page tables inside the
+ * given VMA range readable/writable
+ *
+ * This takes care of mlocking the pages, too, if VM_LOCKED is set.
+ *
+ * @vma: target vma
+ * @start: start address
+ * @end: end address
+ * @write: whether to prefault readable or writable
+ * @locked: whether the mmap_lock is still held
+ *
+ * Returns either number of processed pages in the vma, or a negative error
+ * code on error (see __get_user_pages()).
+ *
+ * vma->vm_mm->mmap_lock must be held. The range must be page-aligned and
+ * covered by the VMA.
+ *
+ * If @locked is NULL, it may be held for read or write and will be unperturbed.
+ *
+ * If @locked is non-NULL, it must held for read only and may be released. If
+ * it's released, *@locked will be set to 0.
+ */
+long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, bool write, int *locked)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long nr_pages = (end - start) / PAGE_SIZE;
+ int gup_flags;
+
+ VM_BUG_ON(!PAGE_ALIGNED(start));
+ VM_BUG_ON(!PAGE_ALIGNED(end));
+ VM_BUG_ON_VMA(start < vma->vm_start, vma);
+ VM_BUG_ON_VMA(end > vma->vm_end, vma);
+ mmap_assert_locked(mm);
+
+ /*
+ * FOLL_TOUCH: Mark page accessed and thereby young; will also mark
+ * the page dirty with FOLL_WRITE -- which doesn't make a
+ * difference with !FOLL_FORCE, because the page is writable
+ * in the page table.
+ * FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit
+ * a poisoned page.
+ * FOLL_POPULATE: Always populate memory with VM_LOCKONFAULT.
+ * !FOLL_FORCE: Require proper access permissions.
+ */
+ gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK | FOLL_HWPOISON;
+ if (write)
+ gup_flags |= FOLL_WRITE;
+
+ /*
+ * See check_vma_flags(): Will return -EFAULT on incompatible mappings
+ * or with insufficient permissions.
+ */
+ return __get_user_pages(mm, start, nr_pages, gup_flags,
+ NULL, NULL, locked);
+}
+
+/*
* __mm_populate - populate and/or mlock pages within a range of address space.
*
* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap