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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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c801ed3860
The use of #defines with '##' pre-processor concatenation is a useful way to form several symbol names with a common pattern. But when there is just a single name obtained from that #define, it's just obfuscation. Better to just write the plain symbol name, as is. The following patch is a result of my wasting ten minutes looking through the kernel to figure out what 'PB_migrate_end' meant, and forgetting what I came to do, by the time I figured out that the #define PB_range macro defined it. Signed-off-by: Paul Jackson <pj@sgi.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
74 lines
2.2 KiB
C
74 lines
2.2 KiB
C
/*
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* Macros for manipulating and testing flags related to a
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* pageblock_nr_pages number of pages.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation version 2 of the License
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2006
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*
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* Original author, Mel Gorman
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* Major cleanups and reduction of bit operations, Andy Whitcroft
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*/
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#ifndef PAGEBLOCK_FLAGS_H
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#define PAGEBLOCK_FLAGS_H
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#include <linux/types.h>
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/* Bit indices that affect a whole block of pages */
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enum pageblock_bits {
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PB_migrate,
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PB_migrate_end = PB_migrate + 3 - 1,
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/* 3 bits required for migrate types */
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NR_PAGEBLOCK_BITS
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};
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#ifdef CONFIG_HUGETLB_PAGE
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#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
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/* Huge page sizes are variable */
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extern int pageblock_order;
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#else /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
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/* Huge pages are a constant size */
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#define pageblock_order HUGETLB_PAGE_ORDER
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#endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */
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#else /* CONFIG_HUGETLB_PAGE */
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/* If huge pages are not used, group by MAX_ORDER_NR_PAGES */
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#define pageblock_order (MAX_ORDER-1)
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#endif /* CONFIG_HUGETLB_PAGE */
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#define pageblock_nr_pages (1UL << pageblock_order)
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/* Forward declaration */
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struct page;
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/* Declarations for getting and setting flags. See mm/page_alloc.c */
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unsigned long get_pageblock_flags_group(struct page *page,
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int start_bitidx, int end_bitidx);
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void set_pageblock_flags_group(struct page *page, unsigned long flags,
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int start_bitidx, int end_bitidx);
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#define get_pageblock_flags(page) \
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get_pageblock_flags_group(page, 0, NR_PAGEBLOCK_BITS-1)
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#define set_pageblock_flags(page) \
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set_pageblock_flags_group(page, 0, NR_PAGEBLOCK_BITS-1)
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#endif /* PAGEBLOCK_FLAGS_H */
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