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s390/mm: hugetlb pages within a gmap can not be freed 

Guests backed by huge pages could theoretically free unused pages via
the diagnose 10 instruction. We currently don't allow that, so we
don't have to refault it once it's needed again.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
This commit is contained in:
Dominik Dingel 2018-07-13 11:28:29 +01:00 committed by Janosch Frank
parent bd096f6443
commit 7d735b9ae8
1 changed files with 6 additions and 0 deletions
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6
arch/s390/mm/gmap.c
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@ -706,6 +706,12 @@ void gmap_discard(struct gmap *gmap, unsigned long from, unsigned long to)
vmaddr |= gaddr & ~PMD_MASK;
/* Find vma in the parent mm */
vma = find_vma(gmap->mm, vmaddr);
/*
* We do not discard pages that are backed by
* hugetlbfs, so we don't have to refault them.
*/
if (vma && is_vm_hugetlb_page(vma))
continue;
size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK));
zap_page_range(vma, vmaddr, size);
}