+ mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3.patch added to -mm tree

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The patch titled
     Subject: mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3
has been added to the -mm tree.  Its filename is
     mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3.patch

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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3

- add PageHuge check in dissolve_free_huge_page() outside hugetlb_lock
- update comment on dissolve_free_huge_page() about return value

Link: http://lkml.kernel.org/r/1560761476-4651-3-git-send-email-n-horiguchi@xxxxxxxxxxxxx
Reported-by: Chen, Jerry T <jerry.t.chen@xxxxxxxxx>
Tested-by: Chen, Jerry T <jerry.t.chen@xxxxxxxxx>
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Fixes: 6bc9b56433b76 ("mm: fix race on soft-offlining")
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Xishi Qiu <xishi.qiuxishi@xxxxxxxxxxxxxxx>
Cc: "Chen, Jerry T" <jerry.t.chen@xxxxxxxxx>
Cc: "Zhuo, Qiuxu" <qiuxu.zhuo@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>	[4.19+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/hugetlb.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3
+++ a/mm/hugetlb.c
@@ -1510,14 +1510,22 @@ static int free_pool_huge_page(struct hs
 
 /*
  * Dissolve a given free hugepage into free buddy pages. This function does
- * nothing for in-use (including surplus) hugepages. Returns -EBUSY if the
- * dissolution fails because a give page is not a free hugepage, or because
- * free hugepages are fully reserved.
+ * nothing for in-use hugepages and non-hugepages.
+ * This function returns values like below:
+ *
+ *  -EBUSY: failed to dissolved free hugepages or the hugepage is in-use
+ *          (allocated or reserved.)
+ *       0: successfully dissolved free hugepages or the page is not a
+ *          hugepage (considered as already dissolved)
  */
 int dissolve_free_huge_page(struct page *page)
 {
 	int rc = -EBUSY;
 
+	/* Not to disrupt normal path by vainly holding hugetlb_lock */
+	if (!PageHuge(page))
+		return 0;
+
 	spin_lock(&hugetlb_lock);
 	if (!PageHuge(page)) {
 		rc = 0;
_

Patches currently in -mm which might be from n-horiguchi@xxxxxxxxxxxxx are

mm-soft-offline-return-ebusy-if-set_hwpoison_free_buddy_page-fails.patch
mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge.patch
mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge-v3.patch




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