hugetlbfs: check for reserve page count going negative

When modifying hugetlb reserve page count, check for the value going
negative.  This should not happen in practice.  However, if it does
log a message and stack trace to aid in debug.

Orabug: 28734496

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Larry Bassel <larry.bassel@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 801356eca5e4047b35eb5920d130ffcbf3bb4d22..c7ebb5f9aa6ba57e88ec4bf531fbc831053de40b 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -577,7 +577,10 @@ void hugetlb_fix_reserve_counts(struct inode *inode, bool restore_reserve)
        if (restore_reserve && rsv_adjust) {
                struct hstate *h = hstate_inode(inode);
 
-               hugetlb_acct_memory(h, 1);
+               if (hugetlb_acct_memory(h, 1)) {
+                       printk(KERN_ALERT "HUGERSV hugetlb_fix_reserve_counts: hugetlb_acct_memory failure!!!\n");
+                       dump_stack();
+               }
        }
 }
 
@@ -936,6 +939,10 @@ retry_cpuset:
                                        break;
 
                                SetPagePrivate(page);
+                               if (!h->resv_huge_pages) {
+                                       printk(KERN_ALERT "HUGERSV dequeue_huge_page_vma: resv_huge_pages going negative!!!\n");
+                                       dump_stack();
+                               }
                                h->resv_huge_pages--;
                                break;
                        }
@@ -1585,6 +1592,10 @@ static int gather_surplus_pages(struct hstate *h, int delta)
 
        needed = (h->resv_huge_pages + delta) - h->free_huge_pages;
        if (needed <= 0) {
+               if (((long)(h->resv_huge_pages) + (long)delta) < 0) {
+                       printk(KERN_ALERT "HUGERSV gather_surplus_pages: resv_huge_pages going negative!!!\n");
+                       dump_stack();
+               }
                h->resv_huge_pages += delta;
                return 0;
        }
@@ -1631,6 +1642,10 @@ retry:
         * before they are reserved.
         */
        needed += allocated;
+       if (((long)(h->resv_huge_pages) + (long)delta) < 0) {
+               printk(KERN_ALERT "HUGERSV gather_surplus_pages: resv_huge_pages going negative!!!\n");
+               dump_stack();
+       }
        h->resv_huge_pages += delta;
        ret = 0;
 
@@ -1669,6 +1684,10 @@ static void return_unused_surplus_pages(struct hstate *h,
        unsigned long nr_pages;
 
        /* Uncommit the reservation */
+       if (((long)(h->resv_huge_pages) - (long)unused_resv_pages) < 0) {
+               printk(KERN_ALERT "HUGERSV return_unused_surplus_pages: resv_huge_pages going negative!!!\n");
+               dump_stack();
+       }
        h->resv_huge_pages -= unused_resv_pages;
 
        /* Cannot return gigantic pages currently */
@@ -1929,20 +1948,26 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
        set_page_private(page, (unsigned long)spool);
 
        map_commit = vma_commit_reservation(h, vma, addr);
-       if (unlikely(map_chg > map_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;
+       if (unlikely(map_chg != map_commit)) {
+               if (unlikely(map_chg > map_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);
+                       rsv_adjust = hugepage_subpool_put_pages(spool, 1);
+                       hugetlb_acct_memory(h, -rsv_adjust);
+               } else {
+                       /* map_chg < map_commit */
+                       printk(KERN_ALERT "HUGERSV alloc_huge_page: map_chg < map_commit!!!\n");
+                       dump_stack();
+               }
        }
        return page;
 
@@ -4239,19 +4264,25 @@ int hugetlb_reserve_pages(struct inode *inode,
        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);
+               if (unlikely(chg != add)) {
+                       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);
+                       } else {
+                               /* chg < add */
+                               printk(KERN_ALERT "HUGERSV hugetlb_reserve_pages: chg < add !!!\n");
+                               dump_stack();
+                       }
                }
        }
        return 0;