Mike Kravetz 3489dbb696 mm: hugetlb: proc: check for hugetlb shared PMD in /proc/PID/smaps
Patch series "Fixes for hugetlb mapcount at most 1 for shared PMDs".

This issue of mapcount in hugetlb pages referenced by shared PMDs was
discussed in [1].  The following two patches address user visible behavior
caused by this issue.

[1] https://lore.kernel.org/linux-mm/Y9BF+OCdWnCSilEu@monkey/


This patch (of 2):

A hugetlb page will have a mapcount of 1 if mapped by multiple processes
via a shared PMD.  This is because only the first process increases the
map count, and subsequent processes just add the shared PMD page to their
page table.

page_mapcount is being used to decide if a hugetlb page is shared or
private in /proc/PID/smaps.  Pages referenced via a shared PMD were
incorrectly being counted as private.

To fix, check for a shared PMD if mapcount is 1.  If a shared PMD is found
count the hugetlb page as shared.  A new helper to check for a shared PMD
is added.

[akpm@linux-foundation.org: simplification, per David]
[akpm@linux-foundation.org: hugetlb.h: include page_ref.h for page_count()]
Link: https://lkml.kernel.org/r/20230126222721.222195-2-mike.kravetz@oracle.com
Fixes: 25ee01a2fca0 ("mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-31 16:44:09 -08:00
..
2022-12-23 11:39:18 -08:00
2023-01-06 12:01:49 -08:00
2022-12-13 10:43:59 -08:00
2022-12-12 20:14:04 -08:00
2022-12-15 18:14:21 -08:00
\n
2022-12-12 20:32:50 -08:00
2022-12-13 19:29:45 -08:00
2023-01-31 16:44:08 -08:00
2022-12-13 19:29:45 -08:00
2022-12-17 08:18:04 -06:00
2022-12-13 19:29:45 -08:00
2022-12-11 18:12:18 -08:00
2022-12-14 10:11:51 -08:00
2022-10-20 10:13:27 +02:00
2022-12-13 19:29:45 -08:00
2022-12-12 20:54:39 -08:00
2022-09-24 07:00:00 +02:00
2023-01-07 10:38:11 -08:00
2023-01-10 15:03:06 -06:00
2022-12-11 18:12:18 -08:00
2022-12-12 20:18:26 -08:00
2022-12-23 11:55:54 -08:00
2022-10-10 19:45:17 -07:00
2022-12-13 09:47:48 -08:00
2022-05-09 16:21:46 -04:00
2023-01-06 15:44:32 +01:00
2022-09-11 20:26:07 -07:00
2023-01-05 07:34:21 -08:00
2022-11-25 17:01:22 +09:00
2022-10-20 10:13:27 +02:00
2022-12-14 12:20:00 -08:00
2022-08-20 11:34:33 -04:00
2022-12-11 18:12:17 -08:00
2022-10-10 19:45:17 -07:00
2022-12-12 19:20:05 -08:00
2022-12-15 18:09:48 -08:00
2022-12-12 19:20:05 -08:00
2022-12-12 19:03:10 -08:00
2022-04-01 19:35:56 -07:00
2022-10-10 14:21:11 -07:00
2022-08-03 10:35:43 -07:00
2022-12-13 09:14:50 -08:00
2022-12-12 19:30:18 -08:00
2022-12-13 09:14:50 -08:00
2022-12-21 14:45:25 +01:00
2022-12-12 19:30:18 -08:00
2022-06-28 13:58:05 -04:00
2022-12-13 10:26:38 -08:00
2022-10-26 10:02:34 +02:00
2022-12-12 18:38:47 -08:00