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[PATCH] mm: split highorder pages

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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>
This commit is contained in:
Nick Piggin
2006-03-22 00:08:05 -08:00
committed by Linus Torvalds
parent 8e7a9aae91
commit 8dfcc9ba27
9 changed files with 41 additions and 21 deletions
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22
mm/page_alloc.c
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@@ -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