From 33f2ef89f8e181486b63fdbdc97c6afa6ca9f34b Mon Sep 17 00:00:00 2001 From: Andy Whitcroft Date: Wed, 6 Dec 2006 20:33:32 -0800 Subject: [PATCH] [PATCH] mm: make compound page destructor handling explicit Currently we we use the lru head link of the second page of a compound page to hold its destructor. This was ok when it was purely an internal implmentation detail. However, hugetlbfs overrides this destructor violating the layering. Abstract this out as explicit calls, also introduce a type for the callback function allowing them to be type checked. For each callback we pre-declare the function, causing a type error on definition rather than on use elsewhere. [akpm@osdl.org: cleanups] Signed-off-by: Andy Whitcroft Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 18 ++++++++++++++++++ mm/hugetlb.c | 2 +- mm/page_alloc.c | 2 +- mm/swap.c | 4 ++-- 4 files changed, 22 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 0e266fe1b4c4..a17b147c61e7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -295,6 +295,24 @@ void put_pages_list(struct list_head *pages); void split_page(struct page *page, unsigned int order); +/* + * Compound pages have a destructor function. Provide a + * prototype for that function and accessor functions. + * These are _only_ valid on the head of a PG_compound page. + */ +typedef void compound_page_dtor(struct page *); + +static inline void set_compound_page_dtor(struct page *page, + compound_page_dtor *dtor) +{ + page[1].lru.next = (void *)dtor; +} + +static inline compound_page_dtor *get_compound_page_dtor(struct page *page) +{ + return (compound_page_dtor *)page[1].lru.next; +} + /* * Multiple processes may "see" the same page. E.g. for untouched * mappings of /dev/null, all processes see the same page full of diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2911a364481e..0ccc7f230252 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -109,7 +109,7 @@ static int alloc_fresh_huge_page(void) if (nid == MAX_NUMNODES) nid = first_node(node_online_map); if (page) { - page[1].lru.next = (void *)free_huge_page; /* dtor */ + set_compound_page_dtor(page, free_huge_page); spin_lock(&hugetlb_lock); nr_huge_pages++; nr_huge_pages_node[page_to_nid(page)]++; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dc8753bdd47e..d539f83c62b6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -230,7 +230,7 @@ static void prep_compound_page(struct page *page, unsigned long order) int i; int nr_pages = 1 << order; - page[1].lru.next = (void *)free_compound_page; /* set dtor */ + set_compound_page_dtor(page, free_compound_page); page[1].lru.prev = (void *)order; for (i = 0; i < nr_pages; i++) { struct page *p = page + i; diff --git a/mm/swap.c b/mm/swap.c index d9a3770d8f3c..017e72ca9bbb 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -57,9 +57,9 @@ static void put_compound_page(struct page *page) { page = (struct page *)page_private(page); if (put_page_testzero(page)) { - void (*dtor)(struct page *page); + compound_page_dtor *dtor; - dtor = (void (*)(struct page *))page[1].lru.next; + dtor = get_compound_page_dtor(page); (*dtor)(page); } } -- 2.20.1