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>
Commit cf8e865810 ("arch: Remove Itanium (IA-64) architecture")
removed the last use of the absolute kallsyms.
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/all/20240221202655.2423854-1-jannh@google.com/
[masahiroy@kernel.org: rebase the code and reword the commit description]
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reclaim the Slab page flag by using a spare bit in PageType. We are
perennially short of page flags for various purposes, and now that the
original SLAB allocator has been retired, SLUB does not use the
mapcount/page_type field. This lets us remove a number of special cases
for ignoring mapcount on Slab pages.
[willy@infradead.org: update vmcoreinfo]
Link: https://lkml.kernel.org/r/ZgGV-O8WYQ_83kxp@casper.infradead.org
Link: https://lkml.kernel.org/r/20240321142448.1645400-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The current folio_test_hugetlb() can be fooled by a concurrent folio split
into returning true for a folio which has never belonged to hugetlbfs.
This can't happen if the caller holds a refcount on it, but we have a few
places (memory-failure, compaction, procfs) which do not and should not
take a speculative reference.
Since hugetlb pages do not use individual page mapcounts (they are always
fully mapped and use the entire_mapcount field to record the number of
mappings), the PageType field is available now that page_mapcount()
ignores the value in this field.
In compaction and with CONFIG_DEBUG_VM enabled, the current implementation
can result in an oops, as reported by Luis. This happens since 9c5ccf2db0
("mm: remove HUGETLB_PAGE_DTOR") effectively added some VM_BUG_ON() checks
in the PageHuge() testing path.
[willy@infradead.org: update vmcoreinfo]
Link: https://lkml.kernel.org/r/ZgGZUvsdhaT1Va-T@casper.infradead.org
Link: https://lkml.kernel.org/r/20240321142448.1645400-6-willy@infradead.org
Fixes: 9c5ccf2db0 ("mm: remove HUGETLB_PAGE_DTOR")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Luis Chamberlain <mcgrof@kernel.org>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218227
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In memory_model.h, if CONFIG_SPARSEMEM_VMEMMAP is configed, kernel will
use vmemmap to do the __pfn_to_page/page_to_pfn, and kernel will not use
the "classic sparse" to do the __pfn_to_page/page_to_pfn.
So export the vmemmap when CONFIG_SPARSEMEM_VMEMMAP is configed. This
makes the user applications (crash, etc) get faster
pfn_to_page/page_to_pfn operations too.
Link: https://lkml.kernel.org/r/20240227014952.3184-1-shijie@os.amperecomputing.com
Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Kazuhito Hagio <k-hagio-ab@nec.com>
Cc: Lianbo Jiang <lijiang@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Now move the relevant codes into separate files:
kernel/crash_reserve.c, include/linux/crash_reserve.h.
And add config item CRASH_RESERVE to control its enabling.
And also update the old ifdeffery of CONFIG_CRASH_CORE, including of
<linux/crash_core.h> and config item dependency on CRASH_CORE
accordingly.
And also do renaming as follows:
- arch/xxx/kernel/{crash_core.c => vmcore_info.c}
because they are only related to vmcoreinfo exporting on x86, arm64,
riscv.
And also Remove config item CRASH_CORE, and rely on CONFIG_KEXEC_CORE to
decide if build in crash_core.c.
[yang.lee@linux.alibaba.com: remove duplicated include in vmcore_info.c]
Link: https://lkml.kernel.org/r/20240126005744.16561-1-yang.lee@linux.alibaba.com
Link: https://lkml.kernel.org/r/20240124051254.67105-3-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Michael Kelley <mhklinux@outlook.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
