When a page is used for virtual memory, it is often necessary to obtain
a handler to the corresponding vm_struct, which refers to the virtually
continuous area generated when invoking vmalloc.

The struct page has a "mapping" field, which can be re-used, to store a
pointer to the parent area.

This will avoid more expensive searches, later on.

Signed-off-by: Igor Stoppa <igor.sto...@huawei.com>
---
 include/linux/mm_types.h | 1 +
 mm/vmalloc.c             | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index fd1af6b9591d..c3a4825e10c0 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -84,6 +84,7 @@ struct page {
                void *s_mem;                    /* slab first object */
                atomic_t compound_mapcount;     /* first tail page */
                /* page_deferred_list().next     -- second tail page */
+               struct vm_struct *area;
        };
 
        /* Second double word */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 673942094328..14d99ed22397 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1536,6 +1536,7 @@ static void __vunmap(const void *addr, int 
deallocate_pages)
                        struct page *page = area->pages[i];
 
                        BUG_ON(!page);
+                       page->area = NULL;
                        __free_pages(page, 0);
                }
 
@@ -1744,6 +1745,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned 
long align,
                        const void *caller)
 {
        struct vm_struct *area;
+       unsigned int i;
        void *addr;
        unsigned long real_size = size;
 
@@ -1769,6 +1771,9 @@ void *__vmalloc_node_range(unsigned long size, unsigned 
long align,
 
        kmemleak_vmalloc(area, size, gfp_mask);
 
+       for (i = 0; i < area->nr_pages; i++)
+               area->pages[i]->area = area;
+
        return addr;
 
 fail:
-- 
2.14.1

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