[PATCH 1/6] struct page: add field for vm_struct

[Igor Stoppa]

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>
Reviewed-by: Jay Freyensee <why2jjj.li...@gmail.com>
Reviewed-by: Matthew Wilcox <mawil...@microsoft.com>
---
 include/linux/mm_types.h | 1 +
 mm/vmalloc.c             | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 21612347d311..c74e2aa9a48b 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -86,6 +86,7 @@ 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 ebff729cc956..61a1ca22b0f6 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);
                }
 
@@ -1705,6 +1706,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, 
gfp_t gfp_mask,
                        area->nr_pages = i;
                        goto fail;
                }
+               page->area = area;
                area->pages[i] = page;
                if (gfpflags_allow_blocking(gfp_mask|highmem_mask))
                        cond_resched();
-- 
2.14.1