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

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

[akpm]

The patch titled
     Subject: mm: hugetlb: soft-offline: dissolve_free_huge_page() return zero on !PageHuge
has been added to the -mm tree.  Its filename is
     mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge.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.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge.patch

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------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: mm: hugetlb: soft-offline: dissolve_free_huge_page() return zero on !PageHuge

madvise(MADV_SOFT_OFFLINE) often returns -EBUSY when calling soft offline
for hugepages with overcommitting enabled.  That was caused by the
suboptimal code in current soft-offline code.  See the following part:

    ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL,
                            MIGRATE_SYNC, MR_MEMORY_FAILURE);
    if (ret) {
            ...
    } else {
            /*
             * We set PG_hwpoison only when the migration source hugepage
             * was successfully dissolved, because otherwise hwpoisoned
             * hugepage remains on free hugepage list, then userspace will
             * find it as SIGBUS by allocation failure. That's not expected
             * in soft-offlining.
             */
            ret = dissolve_free_huge_page(page);
            if (!ret) {
                    if (set_hwpoison_free_buddy_page(page))
                            num_poisoned_pages_inc();
            }
    }
    return ret;

Here dissolve_free_huge_page() returns -EBUSY if the migration source page
was freed into buddy in migrate_pages(), but even in that case we actually
has a chance that set_hwpoison_free_buddy_page() succeeds.  So that means
current code gives up offlining too early now.

dissolve_free_huge_page() checks that a given hugepage is suitable for
dissolving, where we should return success for !PageHuge() case because
the given hugepage is considered as already dissolved.

This change also affects other callers of dissolve_free_huge_page(), which
are cleaned up together.

Link: http://lkml.kernel.org/r/1560154686-18497-3-git-send-email-n-horiguchi@ah.jp.nec.com
Fixes: 6bc9b56433b76 ("mm: fix race on soft-offlining")
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Chen, Jerry T <jerry.t.chen@intel.com>
Tested-by: Chen, Jerry T <jerry.t.chen@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Xishi Qiu <xishi.qiuxishi@alibaba-inc.com>
Cc: "Chen, Jerry T" <jerry.t.chen@intel.com>
Cc: "Zhuo, Qiuxu" <qiuxu.zhuo@intel.com>
Cc: <stable@vger.kernel.org>	[4.19+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c        |   15 +++++++++------
 mm/memory-failure.c |    5 +----
 2 files changed, 10 insertions(+), 10 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge
+++ a/mm/hugetlb.c
@@ -1519,7 +1519,12 @@ int dissolve_free_huge_page(struct page
 	int rc = -EBUSY;
 
 	spin_lock(&hugetlb_lock);
-	if (PageHuge(page) && !page_count(page)) {
+	if (!PageHuge(page)) {
+		rc = 0;
+		goto out;
+	}
+
+	if (!page_count(page)) {
 		struct page *head = compound_head(page);
 		struct hstate *h = page_hstate(head);
 		int nid = page_to_nid(head);
@@ -1564,11 +1569,9 @@ int dissolve_free_huge_pages(unsigned lo
 
 	for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order) {
 		page = pfn_to_page(pfn);
-		if (PageHuge(page) && !page_count(page)) {
-			rc = dissolve_free_huge_page(page);
-			if (rc)
-				break;
-		}
+		rc = dissolve_free_huge_page(page);
+		if (rc)
+			break;
 	}
 
 	return rc;
--- a/mm/memory-failure.c~mm-hugetlb-soft-offline-dissolve_free_huge_page-return-zero-on-pagehuge
+++ a/mm/memory-failure.c
@@ -1856,11 +1856,8 @@ static int soft_offline_in_use_page(stru
 
 static int soft_offline_free_page(struct page *page)
 {
-	int rc = 0;
-	struct page *head = compound_head(page);
+	int rc = dissolve_free_huge_page(page);
 
-	if (PageHuge(head))
-		rc = dissolve_free_huge_page(page);
 	if (!rc) {
 		if (set_hwpoison_free_buddy_page(page))
 			num_poisoned_pages_inc();
_

Patches currently in -mm which might be from n-horiguchi@ah.jp.nec.com 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