forked from mirrors/linux
1587db62d8
Tidy things up and delete comments stating the obvious with typos or making no sense. Link: https://lkml.kernel.org/r/20210303071609.797782-2-yuzhao@google.com Signed-off-by: Yu Zhao <yuzhao@google.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
109 lines
3.2 KiB
C
109 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#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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#elif MAX_NR_ZONES <= 8
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#define ZONES_SHIFT 3
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#else
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#error ZONES_SHIFT "Too many zones configured"
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#endif
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#define ZONES_WIDTH ZONES_SHIFT
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#ifdef CONFIG_SPARSEMEM
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#include <asm/sparsemem.h>
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#define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
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#else
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#define SECTIONS_SHIFT 0
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#endif
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#ifndef BUILD_VDSO32_64
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/*
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* page->flags layout:
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*
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* There are five possibilities for how page->flags get laid out. The first
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* pair is for the normal case without sparsemem. The second pair is for
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* sparsemem when there is plenty of space for node and section information.
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* The last is when there is insufficient space in page->flags and a separate
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* lookup is necessary.
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*
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* No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
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* " plus space for last_cpupid: | NODE | ZONE | LAST_CPUPID ... | FLAGS |
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* classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
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* " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | 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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#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
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#define NODES_WIDTH NODES_SHIFT
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#elif defined(CONFIG_SPARSEMEM_VMEMMAP)
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#error "Vmemmap: No space for nodes field in page flags"
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#else
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#define NODES_WIDTH 0
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#endif
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/*
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* Note that this #define MUST have a value so that it can be tested with
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* the IS_ENABLED() macro.
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*/
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#if NODES_SHIFT != 0 && NODES_WIDTH == 0
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#define NODE_NOT_IN_PAGE_FLAGS 1
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#endif
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#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
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#define KASAN_TAG_WIDTH 8
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#else
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#define KASAN_TAG_WIDTH 0
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#endif
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#ifdef CONFIG_NUMA_BALANCING
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#define LAST__PID_SHIFT 8
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#define LAST__PID_MASK ((1 << LAST__PID_SHIFT)-1)
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#define LAST__CPU_SHIFT NR_CPUS_BITS
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#define LAST__CPU_MASK ((1 << LAST__CPU_SHIFT)-1)
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#define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
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#else
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#define LAST_CPUPID_SHIFT 0
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#endif
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#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + KASAN_TAG_WIDTH + LAST_CPUPID_SHIFT \
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<= BITS_PER_LONG - NR_PAGEFLAGS
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#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
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#else
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#define LAST_CPUPID_WIDTH 0
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#endif
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#if LAST_CPUPID_SHIFT != 0 && LAST_CPUPID_WIDTH == 0
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#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
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#endif
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#if ZONES_WIDTH + SECTIONS_WIDTH + NODES_WIDTH + KASAN_TAG_WIDTH + LAST_CPUPID_WIDTH \
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> BITS_PER_LONG - NR_PAGEFLAGS
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#error "Not enough bits in page flags"
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#endif
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#endif
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#endif /* _LINUX_PAGE_FLAGS_LAYOUT */
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