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authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2019-06-28 12:06:56 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-06-29 16:43:45 +0800
commitfaf53def3b143df11062d87c12afe6afeb6f8cc7 (patch)
tree63b2a1920766dd92f9d273713834aef5071d50b2
parentb38e5962f8ed0d2a2b28a887fc2221f7f41db119 (diff)
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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. [n-horiguchi@ah.jp.nec.com: v3] Link: http://lkml.kernel.org/r/1560761476-4651-3-git-send-email-n-horiguchi@ah.jp.nec.comLink: 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> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> 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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/hugetlb.c29
-rw-r--r--mm/memory-failure.c5
2 files changed, 21 insertions, 13 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ac843d32b019..ede7e7f5d1ab 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1510,16 +1510,29 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
/*
* 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) && !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 +1577,9 @@ int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
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;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8ee7b16235ac..d9cc6606f409 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1856,11 +1856,8 @@ static int soft_offline_in_use_page(struct page *page, int flags)
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();