lkml.org 
[lkml]   [2021]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v1 02/11] mm: thp: consolidate mapcount logic on THP split
Date
Let's consolidate the mapcount logic to make it easier to understand and
to prepare for further changes.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/huge_memory.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e5483347291c..4751d03947da 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2101,21 +2101,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
- if (!pmd_migration)
- atomic_inc(&page[i]._mapcount);
pte_unmap(pte);
}

if (!pmd_migration) {
+ /* Sub-page mapcount accounting for above small mappings. */
+ int val = 1;
+
/*
* Set PG_double_map before dropping compound_mapcount to avoid
* false-negative page_mapped().
+ *
+ * The first to set PageDoubleMap() has to increment all
+ * sub-page mapcounts by one.
*/
- if (compound_mapcount(page) > 1 &&
- !TestSetPageDoubleMap(page)) {
- for (i = 0; i < HPAGE_PMD_NR; i++)
- atomic_inc(&page[i]._mapcount);
- }
+ if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page))
+ val++;
+
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ atomic_add(val, &page[i]._mapcount);

lock_page_memcg(page);
if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
--
2.31.1
\
 
 \ /
  Last update: 2021-12-17 12:34    [W:0.621 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site