+ hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: hugetlb: remove unnecessary set_page_count in prep_compound_gigantic_page
has been added to the -mm tree.  Its filename is
     hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page.patch

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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@oracle.com>
Subject: hugetlb: remove unnecessary set_page_count in prep_compound_gigantic_page

In commit 7118fc2906e29 ("hugetlb: address ref count racing in
prep_compound_gigantic_page"), page_ref_freeze is used to atomically zero
the ref count of tail pages iff they are 1.  The unconditional call to
set_page_count(0) was left in the code.  This call is after
page_ref_freeze so it is really a noop.

Remove redundant and unnecessary set_page_count call.

Link: https://lkml.kernel.org/r/20211026220635.35187-1-mike.kravetz@oracle.com
Fixes: 7118fc2906e29 ("hugetlb: address ref count racing in prep_compound_gigantic_page")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |    1 -
 1 file changed, 1 deletion(-)

--- a/mm/hugetlb.c~hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page
+++ a/mm/hugetlb.c
@@ -1792,7 +1792,6 @@ static bool __prep_compound_gigantic_pag
 		} else {
 			VM_BUG_ON_PAGE(page_count(p), p);
 		}
-		set_page_count(p, 0);
 		set_compound_head(p, page);
 	}
 	atomic_set(compound_mapcount_ptr(page), -1);
_

Patches currently in -mm which might be from mike.kravetz@oracle.com are

hugetlb-add-demote-hugetlb-page-sysfs-interfaces.patch
hugetlb-add-demote-hugetlb-page-sysfs-interfaces-fix.patch
mm-cma-add-cma_pages_valid-to-determine-if-pages-are-in-cma.patch
hugetlb-be-sure-to-free-demoted-cma-pages-to-cma.patch
hugetlb-add-demote-bool-to-gigantic-page-routines.patch
hugetlb-add-hugetlb-demote-page-support.patch
hugetlb-add-hugetlb-demote-page-support-v4.patch
hugetlb-remove-unnecessary-set_page_count-in-prep_compound_gigantic_page.patch