Free hugetlb pages are trickier to handle as to in order to guarantee no userspace appplication disruption, we need to replace the current free hugepage with a new one.
In order to do that, a new function called alloc_and_dissolve_huge_page in introduced. This function will first try to get a new fresh hugetlb page, and if it succeeds, it will dissolve the old one. Signed-off-by: Oscar Salvador <[email protected]> --- include/linux/hugetlb.h | 6 ++++++ mm/compaction.c | 11 +++++++++++ mm/hugetlb.c | 35 +++++++++++++++++++++++++++++++++++ 3 files changed, 52 insertions(+) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index ebca2ef02212..f81afcb86e89 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -505,6 +505,7 @@ struct huge_bootmem_page { struct hstate *hstate; }; +bool alloc_and_dissolve_huge_page(struct page *page); struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve); struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, @@ -773,6 +774,11 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma, #else /* CONFIG_HUGETLB_PAGE */ struct hstate {}; +static inline bool alloc_and_dissolve_huge_page(struct page *page) +{ + return false; +} + static inline struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve) diff --git a/mm/compaction.c b/mm/compaction.c index 89cd2e60da29..7969ddc10856 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -952,6 +952,17 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, low_pfn += compound_nr(page) - 1; goto isolate_success_no_list; } + } else { + /* + * Free hugetlb page. Allocate a new one and + * dissolve this is if succeed. + */ + if (alloc_and_dissolve_huge_page(page)) { + unsigned long order = buddy_order_unsafe(page); + + low_pfn += (1UL << order) - 1; + continue; + } } goto isolate_fail; } diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 18f6ee317900..79ffbb64c4ee 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2253,6 +2253,41 @@ static void restore_reserve_on_error(struct hstate *h, } } +bool alloc_and_dissolve_huge_page(struct page *page) +{ + NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL); + struct page *head; + struct hstate *h; + bool ret = false; + int nid; + + if (!nodes_allowed) + return ret; + + spin_lock(&hugetlb_lock); + head = compound_head(page); + h = page_hstate(head); + nid = page_to_nid(head); + spin_unlock(&hugetlb_lock); + + init_nodemask_of_node(nodes_allowed, nid); + + /* + * Before dissolving the page, we need to allocate a new one, + * so the pool remains stable. + */ + if (alloc_pool_huge_page(h, nodes_allowed, NULL)) { + /* + * Ok, we have a free hugetlb-page to replace this + * one. Dissolve the old page. + */ + if (!dissolve_free_huge_page(page)) + ret = true; + } + + return ret; +} + struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr, int avoid_reserve) { -- 2.16.3
