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authorMike Kravetz <mike.kravetz@oracle.com>2015-06-24 16:57:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-24 17:49:44 -0700
commit33039678c8da8133e30ea3250d10ae14701dae2b (patch)
treef4193b8b309d314fa2c09fca917efc3e685f0f74
parentcf3ad20bfeadda693e408d85684790714fc29b08 (diff)
mm/hugetlb: handle races in alloc_huge_page and hugetlb_reserve_pages
alloc_huge_page and hugetlb_reserve_pages use region_chg to calculate the number of pages which will be added to the reserve map. Subpool and global reserve counts are adjusted based on the output of region_chg. Before the pages are actually added to the reserve map, these routines could race and add fewer pages than expected. If this happens, the subpool and global reserve counts are not correct. Compare the number of pages actually added (region_add) to those expected to added (region_chg). If fewer pages are actually added, this indicates a race and adjust counters accordingly. Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Cc: David Rientjes <rientjes@google.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hugetlb.c39
1 files changed, 35 insertions, 4 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index cd3fc4194733..75c0eef52c5d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1542,7 +1542,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
struct hugepage_subpool *spool = subpool_vma(vma);
struct hstate *h = hstate_vma(vma);
struct page *page;
- long chg;
+ long chg, commit;
int ret, idx;
struct hugetlb_cgroup *h_cg;
@@ -1583,7 +1583,22 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
set_page_private(page, (unsigned long)spool);
- vma_commit_reservation(h, vma, addr);
+ commit = vma_commit_reservation(h, vma, addr);
+ if (unlikely(chg > commit)) {
+ /*
+ * The page was added to the reservation map between
+ * vma_needs_reservation and vma_commit_reservation.
+ * This indicates a race with hugetlb_reserve_pages.
+ * Adjust for the subpool count incremented above AND
+ * in hugetlb_reserve_pages for the same page. Also,
+ * the reservation count added in hugetlb_reserve_pages
+ * no longer applies.
+ */
+ long rsv_adjust;
+
+ rsv_adjust = hugepage_subpool_put_pages(spool, 1);
+ hugetlb_acct_memory(h, -rsv_adjust);
+ }
return page;
out_uncharge_cgroup:
@@ -3701,8 +3716,24 @@ int hugetlb_reserve_pages(struct inode *inode,
* consumed reservations are stored in the map. Hence, nothing
* else has to be done for private mappings here
*/
- if (!vma || vma->vm_flags & VM_MAYSHARE)
- region_add(resv_map, from, to);
+ if (!vma || vma->vm_flags & VM_MAYSHARE) {
+ long add = region_add(resv_map, from, to);
+
+ if (unlikely(chg > add)) {
+ /*
+ * pages in this range were added to the reserve
+ * map between region_chg and region_add. This
+ * indicates a race with alloc_huge_page. Adjust
+ * the subpool and reserve counts modified above
+ * based on the difference.
+ */
+ long rsv_adjust;
+
+ rsv_adjust = hugepage_subpool_put_pages(spool,
+ chg - add);
+ hugetlb_acct_memory(h, -rsv_adjust);
+ }
+ }
return 0;
out_err:
if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))