Michal Hocko [off-list ref] writes:

On Fri 16-03-12 23:09:28, Aneesh Kumar K.V wrote:

quoted

From: "Aneesh Kumar K.V" <redacted>

hugepage_activelist will be used to track currently used HugeTLB pages.
We need to find the in-use HugeTLB pages to support memcg removal.
On memcg removal we update the page's memory cgroup to point to
parent cgroup.

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 include/linux/hugetlb.h |    1 +
 mm/hugetlb.c            |   23 ++++++++++++++++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index cbd8dc5..6919100 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h

[...]

quoted

@@ -2319,14 +2322,24 @@ void __unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 		page = pte_page(pte);
 		if (pte_dirty(pte))
 			set_page_dirty(page);
-		list_add(&page->lru, &page_list);
+
+		spin_lock(&hugetlb_lock);
+		list_move(&page->lru, &page_list);
+		spin_unlock(&hugetlb_lock);

Why do we really need the spinlock here?

It does a list_del from hugepage_activelist.

quoted

 	}
 	spin_unlock(&mm->page_table_lock);
 	flush_tlb_range(vma, start, end);
 	mmu_notifier_invalidate_range_end(mm, start, end);
 	list_for_each_entry_safe(page, tmp, &page_list, lru) {
 		page_remove_rmap(page);
-		list_del(&page->lru);
+		/*
+		 * We need to move it back huge page active list. If we are
+		 * holding the last reference, below put_page will move it
+		 * back to free list.
+		 */
+		spin_lock(&hugetlb_lock);
+		list_move(&page->lru, &h->hugepage_activelist);
+		spin_unlock(&hugetlb_lock);

This spinlock usage doesn't look nice but I guess we do not have many
other options.

-aneesh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>