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 <osalvador@xxxxxxx>
---
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
