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Subject[PATCH 1/6] struct page: add field for vm_struct
Date
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.stoppa@huawei.com>
Reviewed-by: Jay Freyensee <why2jjj.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@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 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 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
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