bbeae5b05e
This is a preparation patch for moving page->_last_nid into page->flags that moves page flag layout information to a separate header. This patch is necessary because otherwise there would be a circular dependency between mm_types.h and mm.h. Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Simon Jeons <simon.jeons@gmail.com> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
72 lines
2.1 KiB
C
72 lines
2.1 KiB
C
#ifndef PAGE_FLAGS_LAYOUT_H
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#define PAGE_FLAGS_LAYOUT_H
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#include <linux/numa.h>
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#include <generated/bounds.h>
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/*
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* When a memory allocation must conform to specific limitations (such
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* as being suitable for DMA) the caller will pass in hints to the
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* allocator in the gfp_mask, in the zone modifier bits. These bits
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* are used to select a priority ordered list of memory zones which
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* match the requested limits. See gfp_zone() in include/linux/gfp.h
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*/
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#if MAX_NR_ZONES < 2
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#define ZONES_SHIFT 0
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#elif MAX_NR_ZONES <= 2
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#define ZONES_SHIFT 1
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#elif MAX_NR_ZONES <= 4
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#define ZONES_SHIFT 2
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#else
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#error ZONES_SHIFT -- too many zones configured adjust calculation
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#endif
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#ifdef CONFIG_SPARSEMEM
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#include <asm/sparsemem.h>
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/* SECTION_SHIFT #bits space required to store a section # */
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#define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
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#endif /* CONFIG_SPARSEMEM */
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/*
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* page->flags layout:
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*
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* There are three possibilities for how page->flags get
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* laid out. The first is for the normal case, without
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* sparsemem. The second is for sparsemem when there is
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* plenty of space for node and section. The last is when
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* we have run out of space and have to fall back to an
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* alternate (slower) way of determining the node.
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*
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* No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
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* classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
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* classic sparse no space for node: | SECTION | ZONE | ... | FLAGS |
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*/
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#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
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#define SECTIONS_WIDTH SECTIONS_SHIFT
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#else
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#define SECTIONS_WIDTH 0
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#endif
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#define ZONES_WIDTH ZONES_SHIFT
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#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
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#define NODES_WIDTH NODES_SHIFT
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#else
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#ifdef CONFIG_SPARSEMEM_VMEMMAP
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#error "Vmemmap: No space for nodes field in page flags"
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#endif
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#define NODES_WIDTH 0
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#endif
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/*
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* We are going to use the flags for the page to node mapping if its in
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* there. This includes the case where there is no node, so it is implicit.
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*/
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#if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
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#define NODE_NOT_IN_PAGE_FLAGS
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#endif
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#endif /* _LINUX_PAGE_FLAGS_LAYOUT */
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