From c27fe4c8942d3ca715986f79cc26f44608d7d9fb Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Mon, 25 Jul 2011 17:12:10 -0700 Subject: [PATCH] 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 Cc: Naoya Horiguchi Cc: Hiroyuki Kamezawa Cc: Andrea Arcangeli Cc: Matt Mackall Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 2 ++ mm/pagewalk.c | 3 +++ 2 files changed, 5 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6321e840e21d..3c5505a3bc49 100644 --- 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 index ee4ff87c58c1..f7929406e776 100644 --- 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)