diff options
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory.c | 4 | ||||
| -rw-r--r-- | mm/page_alloc.c | 22 |
2 files changed, 23 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c index 85e80a57db29..6af555c1c42a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1221,9 +1221,7 @@ out: * The page has to be a nice clean _individual_ kernel allocation. * If you allocate a compound page, you need to have marked it as * such (__GFP_COMP), or manually just split the page up yourself - * (which is mainly an issue of doing "set_page_count(page, 1)" for - * each sub-page, and then freeing them one by one when you free - * them rather than freeing it as a compound page). + * (see split_page()). * * NOTE! Traditionally this was done with "remap_pfn_range()" which * took an arbitrary page protection parameter. This doesn't allow diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 102919851353..fc65e87368b3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -752,6 +752,28 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags) clear_highpage(page + i); } +#ifdef CONFIG_MMU +/* + * split_page takes a non-compound higher-order page, and splits it into + * n (1<<order) sub-pages: page[0..n] + * Each sub-page must be freed individually. + * + * Note: this is probably too low level an operation for use in drivers. + * Please consult with lkml before using this in your driver. + */ +void split_page(struct page *page, unsigned int order) +{ + int i; + + BUG_ON(PageCompound(page)); + BUG_ON(!page_count(page)); + for (i = 1; i < (1 << order); i++) { + BUG_ON(page_count(page + i)); + set_page_count(page + i, 1); + } +} +#endif + /* * Really, prep_compound_page() should be called from __rmqueue_bulk(). But * we cheat by calling it from here, in the order > 0 path. Saves a branch |