diff options
| author | Mike Kravetz <mike.kravetz@oracle.com> | 2023-01-26 14:27:20 -0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-31 16:44:09 -0800 |
| commit | 3489dbb696d25602aea8c3e669a6d43b76bd5358 (patch) | |
| tree | 1839fd52a4146e534785c9f830278e6b1525768d /fs | |
| parent | edb5d0cf5525357652aff6eacd9850b8ced07143 (diff) | |
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>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/proc/task_mmu.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e35a0398db63..af1c49ae11b1 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -745,9 +745,7 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask, page = pfn_swap_entry_to_page(swpent); } if (page) { - int mapcount = page_mapcount(page); - - if (mapcount >= 2) + if (page_mapcount(page) >= 2 || hugetlb_pmd_shared(pte)) mss->shared_hugetlb += huge_page_size(hstate_vma(vma)); else mss->private_hugetlb += huge_page_size(hstate_vma(vma)); |