On 2011年11月15日 21:24, Michal Hocko wrote: > On Tue 15-11-11 16:06:16, Wang Sheng-Hui wrote: >> Per the void prep_compound_page(struct page *page, unsigned long order) code, >> compound pages use PG_head/PG_tail, > > This is true only for CONFIG_PAGEFLAGS_EXTENDED otherwise we trick it by > PG_compound & ~PG_reclaim = head page > PG_compound & PG_reclaim = tail page > > Have a look at PG_head_tail_mask > >> and only tail pages point at head page using their ->first_page field. > > This part is correct. > >> >> Signed-off-by: Wang Sheng-Hui <shhuiw@xxxxxxxxx> >> --- >> mm/page_alloc.c | 4 ++-- >> 1 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 6e8ecb6..f645ce8 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -332,8 +332,8 @@ out: >> * >> * The remaining PAGE_SIZE pages are called "tail pages". >> * >> - * All pages have PG_compound set. All pages have their ->private pointing at >> - * the head page (even the head page has this). >> + * Head page has PG_head set, and all tail pages have PG_tail set. All tail >> + * pages have their ->first_page pointing at the head page. >> * >> * The first tail page's ->lru.next holds the address of the compound page's >> * put_page() function. Its ->lru.prev holds the order of allocation. >> -- >> 1.7.1 >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@xxxxxxxxx. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ >> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > Thanks, Michal. New patch generated. [PATCH] mm: cleanup the comment for head/tail pages of compound pages in mm/page_alloc.c Only tail pages point at the head page using their ->first_page fields. Signed-off-by: Wang Sheng-Hui <shhuiw@xxxxxxxxx> --- mm/page_alloc.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6e8ecb6..e7dd848 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -332,8 +332,8 @@ out: * * The remaining PAGE_SIZE pages are called "tail pages". * - * All pages have PG_compound set. All pages have their ->private pointing at - * the head page (even the head page has this). + * All pages have PG_compound set. All tail pages have their ->first_page + * pointing at the head page. * * The first tail page's ->lru.next holds the address of the compound page's * put_page() function. Its ->lru.prev holds the order of allocation. -- 1.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>