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author | Hugh Dickins <hugh@veritas.com> | 2006-02-14 13:52:59 -0800 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-14 16:09:33 -0800 |
commit | d98c7a09843621f1b145ca5ae8ed03ff04085edb (patch) | |
tree | 764b943efb177ca506fad61a63bb9e8cbf56a3a7 /mm | |
parent | 41d78ba55037468e6c86c53e3076d1a74841de39 (diff) | |
download | linux-stable-d98c7a09843621f1b145ca5ae8ed03ff04085edb.tar.gz linux-stable-d98c7a09843621f1b145ca5ae8ed03ff04085edb.tar.bz2 linux-stable-d98c7a09843621f1b145ca5ae8ed03ff04085edb.zip |
[PATCH] compound page: default destructor
Somehow I imagined that calling a NULL destructor would free a compound page
rather than oopsing. No, we must supply a default destructor, __free_pages_ok
using the order noted by prep_compound_page. hugetlb can still replace this
as before with its own free_huge_page pointer.
The case that needs this is not common: rarely does put_compound_page's
put_page_testzero bring the count down to 0. But if get_user_pages is applied
to some part of a compound page, without immediate release (e.g. AIO or
Infiniband), then it's possible for its put_page to come after the containing
vma has been unmapped and the driver done its free_pages.
That's just the kind of case compound pages are supposed to be guarding
against (but Nick points out, nor did PageReserved handle this right).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/page_alloc.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index eec89ab39bb6..62c122528587 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -56,6 +56,7 @@ long nr_swap_pages; int percpu_pagelist_fraction; static void fastcall free_hot_cold_page(struct page *page, int cold); +static void __free_pages_ok(struct page *page, unsigned int order); /* * results with 256, 32 in the lowmem_reserve sysctl: @@ -173,12 +174,18 @@ static void bad_page(struct page *page) * put_page() function. Its ->lru.prev holds the order of allocation. * This usage means that zero-order pages may not be compound. */ + +static void free_compound_page(struct page *page) +{ + __free_pages_ok(page, (unsigned long)page[1].lru.prev); +} + static void prep_compound_page(struct page *page, unsigned long order) { int i; int nr_pages = 1 << order; - page[1].lru.next = NULL; /* set dtor */ + page[1].lru.next = (void *)free_compound_page; /* set dtor */ page[1].lru.prev = (void *)order; for (i = 0; i < nr_pages; i++) { struct page *p = page + i; |