[PATCH 31/36] thp, mm: split_huge_page(): caller need to lock page

[Kirill A. Shutemov]

We're going to use migration entries instead of compound_lock() to
stabilize page refcounts. Setup and remove migration entries require
page to be locked.

Some of split_huge_page() callers already have the page locked. Let's
require everybody to lock the page before calling split_huge_page().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Tested-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/memory-failure.c | 10 ++++++++--
 mm/migrate.c        |  8 ++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 1cf7f2988422..0d9989a36d32 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1143,15 +1143,18 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 				put_page(hpage);
 			return -EBUSY;
 		}
+		lock_page(hpage);
 		if (unlikely(split_huge_page(hpage))) {
 			pr_err("MCE: %#lx: thp split failed\n", pfn);
 			if (TestClearPageHWPoison(p))
 				atomic_long_sub(nr_pages, &num_poisoned_pages);
+			unlock_page(hpage);
 			put_page(p);
 			if (p != hpage)
 				put_page(hpage);
 			return -EBUSY;
 		}
+		unlock_page(hpage);
 		VM_BUG_ON_PAGE(!page_count(p), p);
 		hpage = compound_head(p);
 	}
@@ -1714,10 +1717,13 @@ int soft_offline_page(struct page *page, int flags)
 		return -EBUSY;
 	}
 	if (!PageHuge(page) && PageTransHuge(hpage)) {
-		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+		lock_page(page);
+		ret = split_huge_page(hpage);
+		unlock_page(page);
+		if (unlikely(ret)) {
 			pr_info("soft offline: %#lx: failed to split THP\n",
 				pfn);
-			return -EBUSY;
+			return ret;
 		}
 	}
 
diff --git a/mm/migrate.c b/mm/migrate.c
index dfd24cb7afc6..8bb2107b8751 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -933,9 +933,13 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
 		goto out;
 	}
 
-	if (unlikely(PageTransHuge(page)))
-		if (unlikely(split_huge_page(page)))
+	if (unlikely(PageTransHuge(page))) {
+		lock_page(page);
+		rc = split_huge_page(page);
+		unlock_page(page);
+		if (rc)
 			goto out;
+	}
 
 	rc = __unmap_and_move(page, newpage, force, mode);
 
-- 
2.1.4

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