[PATCH] hugetlb: Add documentation for vma_kernel_pagesize()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

This is an exported symbol, so it should have kernel-doc.  Update
it to mention folios, and point out that they might be larger than
the supported page size for this VMA.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/hugetlb.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 283cd5290515..dfadb3bfd284 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -968,9 +968,14 @@ pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL_GPL(linear_hugepage_index);
 
-/*
- * Return the size of the pages allocated when backing a VMA. In the majority
- * cases this will be same size as used by the page table entries.
+/**
+ * vma_kernel_pagesize - Page size granularity for this VMA.
+ * @vma: The user mapping.
+ *
+ * Folios in this VMA will be aligned to, and at least the size of the
+ * number of bytes returned by this function.
+ *
+ * Return: The default size of the folios allocated when backing a VMA.
  */
 unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
 {
-- 
2.40.1