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mm: support only one page_type per page

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By using a few values in the top byte, users of page_type can store up to
24 bits of additional data in page_type.  It also reduces the code size as
(with replacement of READ_ONCE() with data_race()), the kernel can check
just a single byte.  eg:

ffffffff811e3a79:       8b 47 30                mov    0x30(%rdi),%eax
ffffffff811e3a7c:       55                      push   %rbp
ffffffff811e3a7d:       48 89 e5                mov    %rsp,%rbp
ffffffff811e3a80:       25 00 00 00 82          and    $0x82000000,%eax
ffffffff811e3a85:       3d 00 00 00 80          cmp    $0x80000000,%eax
ffffffff811e3a8a:       74 4d                   je     ffffffff811e3ad9 <folio_mapping+0x69>

becomes:

ffffffff811e3a69:       80 7f 33 f5             cmpb   $0xf5,0x33(%rdi)
ffffffff811e3a6d:       55                      push   %rbp
ffffffff811e3a6e:       48 89 e5                mov    %rsp,%rbp
ffffffff811e3a71:       74 4d                   je     ffffffff811e3ac0 <folio_mapping+0x60>

replacing three instructions with one.

[wangkefeng.wang@huawei.com: fix ubsan warnings]
  Link: https://lkml.kernel.org/r/2d19c48a-c550-4345-bf36-d05cd303c5de@huawei.com
Link: https://lkml.kernel.org/r/20240821173914.2270383-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle)
2024-08-21 18:39:11 +01:00
committed by Andrew Morton
parent e880034cf7
commit 4ffca5a966
3 changed files with 55 additions and 50 deletions
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8
kernel/vmcore_info.c
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@@ -198,17 +198,17 @@ static int __init crash_save_vmcoreinfo_init(void)
VMCOREINFO_NUMBER(PG_private);
VMCOREINFO_NUMBER(PG_swapcache);
VMCOREINFO_NUMBER(PG_swapbacked);
#define PAGE_SLAB_MAPCOUNT_VALUE (~PG_slab)
#define PAGE_SLAB_MAPCOUNT_VALUE (PGTY_slab << 24)
VMCOREINFO_NUMBER(PAGE_SLAB_MAPCOUNT_VALUE);
#ifdef CONFIG_MEMORY_FAILURE
VMCOREINFO_NUMBER(PG_hwpoison);
#endif
VMCOREINFO_NUMBER(PG_head_mask);
#define PAGE_BUDDY_MAPCOUNT_VALUE (~PG_buddy)
#define PAGE_BUDDY_MAPCOUNT_VALUE (PGTY_buddy << 24)
VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
#define PAGE_HUGETLB_MAPCOUNT_VALUE (~PG_hugetlb)
#define PAGE_HUGETLB_MAPCOUNT_VALUE (PGTY_hugetlb << 24)
VMCOREINFO_NUMBER(PAGE_HUGETLB_MAPCOUNT_VALUE);
#define PAGE_OFFLINE_MAPCOUNT_VALUE (~PG_offline)
#define PAGE_OFFLINE_MAPCOUNT_VALUE (PGTY_offline << 24)
VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE);
#ifdef CONFIG_KALLSYMS