From 1fb1b0e9ef2d661488f8053986c3b7641cae529d Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Tue, 8 Sep 2015 15:01:44 -0700 Subject: [PATCH] mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch In vma_has_reserves(), the current assumption is that reserves are always present for shared mappings. However, this will not be the case with fallocate hole punch. When punching a hole, the present page will be deleted as well as the region/reserve map entry (and hence any reservation). vma_has_reserves is passed "chg" which indicates whether or not a region/reserve map is present. Use this to determine if reserves are actually present or were removed via hole punch. Signed-off-by: Mike Kravetz Reviewed-by: Naoya Horiguchi Acked-by: Hillf Danton Cc: Dave Hansen Cc: David Rientjes Cc: Hugh Dickins Cc: Davidlohr Bueso Cc: Aneesh Kumar Cc: Christoph Hellwig Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/hugetlb.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 61c52cd5f77b..bd12e8c8bc7b 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -801,8 +801,19 @@ static bool vma_has_reserves(struct vm_area_struct *vma, long chg) } /* Shared mappings always use reserves */ - if (vma->vm_flags & VM_MAYSHARE) - return true; + if (vma->vm_flags & VM_MAYSHARE) { + /* + * We know VM_NORESERVE is not set. Therefore, there SHOULD + * be a region map for all pages. The only situation where + * there is no region map is if a hole was punched via + * fallocate. In this case, there really are no reverves to + * use. This situation is indicated if chg != 0. + */ + if (chg) + return false; + else + return true; + } /* * Only the process that called mmap() has reserves for -- 2.20.1