Commit 1fb1b0e9 authored Sep 08, 2015 by Mike Kravetz Committed by Linus Torvalds Sep 08, 2015

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 <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b5cec28d

mm/hugetlb.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -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)
		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

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