diff options
Diffstat (limited to 'mm')
-rw-r--r-- | mm/hugetlb.c | 37 |
1 files changed, 28 insertions, 9 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3edb759..c7025c1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1773,23 +1773,32 @@ free: } /* - * When releasing a hugetlb pool reservation, any surplus pages that were - * allocated to satisfy the reservation must be explicitly freed if they were - * never used. - * Called with hugetlb_lock held. + * This routine has two main purposes: + * 1) Decrement the reservation count (resv_huge_pages) by the value passed + * in unused_resv_pages. This corresponds to the prior adjustments made + * to the associated reservation map. + * 2) Free any unused surplus pages that may have been allocated to satisfy + * the reservation. As many as unused_resv_pages may be freed. + * + * Called with hugetlb_lock held. However, the lock could be dropped (and + * reacquired) during calls to cond_resched_lock. Whenever dropping the lock, + * we must make sure nobody else can claim pages we are in the process of + * freeing. Do this by ensuring resv_huge_page always is greater than the + * number of huge pages we plan to free when dropping the lock. */ static void return_unused_surplus_pages(struct hstate *h, unsigned long unused_resv_pages) { unsigned long nr_pages; - /* Uncommit the reservation */ - h->resv_huge_pages -= unused_resv_pages; - /* Cannot return gigantic pages currently */ if (hstate_is_gigantic(h)) - return; + goto out; + /* + * Part (or even all) of the reservation could have been backed + * by pre-allocated pages. Only free surplus pages. + */ nr_pages = min(unused_resv_pages, h->surplus_huge_pages); /* @@ -1799,12 +1808,22 @@ static void return_unused_surplus_pages(struct hstate *h, * when the nodes with surplus pages have no free pages. * free_pool_huge_page() will balance the the freed pages across the * on-line nodes with memory and will handle the hstate accounting. + * + * Note that we decrement resv_huge_pages as we free the pages. If + * we drop the lock, resv_huge_pages will still be sufficiently large + * to cover subsequent pages we may free. */ while (nr_pages--) { + h->resv_huge_pages--; + unused_resv_pages--; if (!free_pool_huge_page(h, &node_states[N_MEMORY], 1)) - break; + goto out; cond_resched_lock(&hugetlb_lock); } + +out: + /* Fully uncommit the reservation */ + h->resv_huge_pages -= unused_resv_pages; } |