hugetlb: fix quota management for private mappings (c79fb75e) · Commits · 戴 / test

The hugetlbfs quota management system was never taught to handle MAP_PRIVATE mappings when that support was added. Currently, quota is debited at page instantiation and credited at file truncation. This approach works correctly for shared pages but is incomplete for private pages. In addition to hugetlb_no_page(), private pages can be instantiated by hugetlb_cow(); but this function does not respect quotas. Private huge pages are treated very much like normal, anonymous pages. They are not "backed" by the hugetlbfs file and are not stored in the mapping's radix tree. This means that private pages are invisible to truncate_hugepages() so that function will not credit the quota. This patch (based on a prototype provided by Ken Chen) moves quota crediting for all pages into free_huge_page(). page->private is used to store a pointer to the mapping to which this page belongs. This is used to credit quota on the appropriate hugetlbfs instance. Signed-off-by:

Adam Litke <agl@us.ibm.com> Cc: Ken Chen <kenchen@google.com> Cc: Ken Chen <kenchen@google.com> Cc: Andy Whitcroft <apw@shadowen.org> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: David Gibson <hermes@gibson.dropbear.id.au> Cc: William Lee Irwin III <wli@holomorphy.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/hugetlbfs/inode.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -364,7 +364,6 @@ static void truncate_hugepages(struct inode *inode, loff_t lstart)
		++next;
		truncate_huge_page(page);
		unlock_page(page);
		hugetlb_put_quota(mapping);
		freed++;
		}
		huge_pagevec_release(&pvec);

mm/hugetlb.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -116,7 +116,9 @@ static void update_and_free_page(struct page *page)
		static void free_huge_page(struct page *page)
		{
		int nid = page_to_nid(page);
		struct address_space *mapping;

		mapping = (struct address_space *) page_private(page);
		BUG_ON(page_count(page));
		INIT_LIST_HEAD(&page->lru);

		@@ -129,6 +131,9 @@ static void free_huge_page(struct page *page)
		enqueue_huge_page(page);
		}
		spin_unlock(&hugetlb_lock);
		if (mapping)
		hugetlb_put_quota(mapping);
		set_page_private(page, 0);
		}

		/*
		@@ -388,8 +393,10 @@ static struct page alloc_huge_page(struct vm_area_struct vma,
		page = alloc_huge_page_shared(vma, addr);
		else
		page = alloc_huge_page_private(vma, addr);
		if (page)
		if (page) {
		set_page_refcounted(page);
		set_page_private(page, (unsigned long) vma->vm_file->f_mapping);
		}
		return page;
		}

		@@ -730,6 +737,8 @@ static int hugetlb_cow(struct mm_struct mm, struct vm_area_struct vma,
		set_huge_ptep_writable(vma, address, ptep);
		return 0;
		}
		if (hugetlb_get_quota(vma->vm_file->f_mapping))
		return VM_FAULT_SIGBUS;

		page_cache_get(old_page);
		new_page = alloc_huge_page(vma, address);
		@@ -796,7 +805,6 @@ retry:
		err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
		if (err) {
		put_page(page);
		hugetlb_put_quota(mapping);
		if (err == -EEXIST)
		goto retry;
		goto out;
		@@ -830,7 +838,6 @@ out:

		backout:
		spin_unlock(&mm->page_table_lock);
		hugetlb_put_quota(mapping);
		unlock_page(page);
		put_page(page);
		goto out;

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