From: Mel Gorman Date: Thu, 24 Jul 2008 04:27:58 +0000 (-0700) Subject: hugetlb: fix a hugepage reservation check for MAP_SHARED X-Git-Tag: v2.6.27-rc1~777 X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=7f09ca51e925ba62e9ebfd4979f093e97e38adeb;ds=sidebyside hugetlb: fix a hugepage reservation check for MAP_SHARED When removing a huge page from the hugepage pool for a fault the system checks to see if the mapping requires additional pages to be reserved, and if it does whether there are any unreserved pages remaining. If not, the allocation fails without even attempting to get a page. In order to determine whether to apply this check we call vma_has_private_reserves() which tells us if this vma is MAP_PRIVATE and is the owner. This incorrectly triggers the remaining reservation test for MAP_SHARED mappings which prevents allocation of the final page in the pool even though it is reserved for this mapping. In reality we only want to check this for MAP_PRIVATE mappings where the process is not the original mapper. Replace vma_has_private_reserves() with vma_has_reserves() which indicates whether further reserves are required, and update the caller. Signed-off-by: Mel Gorman Acked-by: Adam Litke Acked-by: Andy Whitcroft Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3e1506b808a3..8c20aed62b9c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -342,13 +342,13 @@ void reset_vma_resv_huge_pages(struct vm_area_struct *vma) } /* Returns true if the VMA has associated reserve pages */ -static int vma_has_private_reserves(struct vm_area_struct *vma) +static int vma_has_reserves(struct vm_area_struct *vma) { if (vma->vm_flags & VM_SHARED) - return 0; - if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) - return 0; - return 1; + return 1; + if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) + return 1; + return 0; } static void clear_huge_page(struct page *page, @@ -420,7 +420,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h, * have no page reserves. This check ensures that reservations are * not "stolen". The child may still get SIGKILLed */ - if (!vma_has_private_reserves(vma) && + if (!vma_has_reserves(vma) && h->free_huge_pages - h->resv_huge_pages == 0) return NULL;