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Matthew Wilcox (Oracle) d99e3140a4 mm: turn folio_test_hugetlb into a PageType 
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>
 		2024-04-24 19:34:26 -07:00
..
events mm: turn folio_test_hugetlb into a PageType 2024-04-24 19:34:26 -07:00
misc NFS client updates for Linux 6.9 2024-03-16 11:44:00 -07:00
stages tracing: Just use strcmp() for testing __string() and __assign_str() match 2024-03-19 11:23:30 -07:00
bpf_probe.h kernel.h: split out COUNT_ARGS() and CONCATENATE() to args.h 2023-08-18 10:18:56 -07:00
define_custom_trace.h tracing: Add TRACE_CUSTOM_EVENT() macro 2022-03-11 11:49:24 -05:00
define_trace.h
…
perf.h perf/tracing: Use stage6 of tracing to not duplicate macros 2023-01-25 10:31:24 -05:00
syscall.h
…
trace_custom_events.h tracing: Rename the staging files for trace_events 2022-04-02 08:40:04 -04:00
trace_events.h tracing: Rename the staging files for trace_events 2022-04-02 08:40:04 -04:00