Areas hole punched by fallocate will not have entries in the
region/reserve map. However, shared mappings with min_size subpool
reservations may still have reserved pages. alloc_huge_page needs
to handle this special case and do the proper accounting.
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/hugetlb.c | 48 +++++++++++++++++++++++++++---------------------
1 file changed, 27 insertions(+), 21 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ecbaffe..9c295c9 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -692,19 +692,9 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
return 0;
}
- 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 0;
- else
- return 1;
- }
+ /* Shared mappings always use reserves */
+ if (vma->vm_flags & VM_MAYSHARE)
+ return 1;
/*
* Only the process that called mmap() has reserves for
@@ -1601,6 +1591,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
struct hstate *h = hstate_vma(vma);
struct page *page;
long chg, commit;
+ long gbl_chg;
int ret, idx;
struct hugetlb_cgroup *h_cg;
@@ -1608,24 +1599,39 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
/*
* Processes that did not create the mapping will have no
* reserves and will not have accounted against subpool
- * limit. Check that the subpool limit can be made before
- * satisfying the allocation MAP_NORESERVE mappings may also
- * need pages and subpool limit allocated allocated if no reserve
- * mapping overlaps.
+ * limit. Check that the subpool limit will not be exceeded
+ * before performing the allocation. Allocations for
+ * MAP_NORESERVE mappings also need to be checked against
+ * any subpool limit.
+ *
+ * NOTE: Shared mappings with holes punched via fallocate
+ * may still have reservations, even without entries in the
+ * reserve map as indicated by vma_needs_reservation. This
+ * would be the case if hugepage_subpool_get_pages returns
+ * zero to indicate no changes to the global reservation count
+ * are necessary. In this case, pass the output of
+ * hugepage_subpool_get_pages (zero) to dequeue_huge_page_vma
+ * so that the page is not counted against the global limit.
+ * For MAP_NORESERVE mappings always pass the output of
+ * vma_needs_reservation. For race detection and error cleanup
+ * use output of vma_needs_reservation as well.
*/
- chg = vma_needs_reservation(h, vma, addr);
+ chg = gbl_chg = vma_needs_reservation(h, vma, addr);
if (chg < 0)
return ERR_PTR(-ENOMEM);
- if (chg || avoid_reserve)
- if (hugepage_subpool_get_pages(spool, 1) < 0)
+ if (chg || avoid_reserve) {
+ gbl_chg = hugepage_subpool_get_pages(spool, 1);
+ if (gbl_chg < 0)
return ERR_PTR(-ENOSPC);
+ }
ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
if (ret)
goto out_subpool_put;
spin_lock(&hugetlb_lock);
- page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg);
+ page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve,
+ avoid_reserve ? chg : gbl_chg);
if (!page) {
spin_unlock(&hugetlb_lock);
page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
--
2.1.0
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>