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| author | Nick Piggin <npiggin@suse.de> | 2006-03-22 00:08:05 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-22 07:53:57 -0800 |
| commit | 8dfcc9ba27e2ed257e5de9539f7f03e57c2c0e33 (patch) | |
| tree | aecaeb6a0b33c23f79dfcd2418e4a3881a29f2e2 /mm | |
| parent | 8e7a9aae91101916b86de07fafe3272ea8dc1f10 (diff) | |
| download | lwn-8dfcc9ba27e2ed257e5de9539f7f03e57c2c0e33.tar.gz lwn-8dfcc9ba27e2ed257e5de9539f7f03e57c2c0e33.zip | |
[PATCH] mm: split highorder pages
Have an explicit mm call to split higher order pages into individual pages.
Should help to avoid bugs and be more explicit about the code's intention.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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 |