pagewalk: add locking-rule comments

Originally, walk_hugetlb_range() didn't require a caller take any lock. But commit d33b9f4 ("mm: hugetlb: fix hugepage memory leak in walk_page_range") changed its rule. Because it added find_vma() call in walk_hugetlb_range(). Any locking-rule change commit should write a doc too. [[email protected]: clarify comment] Signed-off-by: KOSAKI Motohiro <[email protected]> Cc: Naoya Horiguchi <[email protected]> Cc: Hiroyuki Kamezawa <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Matt Mackall <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
opendata26 · Jul 26, 2011 · c27fe4c · c27fe4c
1 parent 6c6d528
commit c27fe4c
Show file tree

Hide file tree

Showing 2 changed files with 5 additions and 0 deletions.
diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -911,6 +911,8 @@ unsigned long unmap_vmas(struct mmu_gather *tlb,
  * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
  * @pte_hole: if set, called for each hole at all levels
  * @hugetlb_entry: if set, called for each hugetlb entry
+ *		   *Caution*: The caller must hold mmap_sem() if @hugetlb_entry
+ * 			      is used.
  *
  * (see walk_page_range for more details)
  */

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
@@ -181,6 +181,9 @@ static int walk_hugetlb_range(struct vm_area_struct *vma,
  *
  * If any callback returns a non-zero value, the walk is aborted and
  * the return value is propagated back to the caller. Otherwise 0 is returned.
+ *
+ * walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
+ * is !NULL.
  */
 int walk_page_range(unsigned long addr, unsigned long end,
 		    struct mm_walk *walk)