pagewalk: add locking-rule comments
Originally, walk_hugetlb_range() didn't require a caller take any lock.
But commit d33b9f45bd ("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.
[akpm@linux-foundation.org: clarify comment]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6321e84..3c5505a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -911,6 +911,8 @@
* @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
index ee4ff87..f792940 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -181,6 +181,9 @@
*
* 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)