linux-kernel - [PATCH 3/3] mm/migrate: add stable check in migrate_vma_insert

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Date:   Tue, 7 Jan 2020 13:12:08 -0800
From:   Ralph Campbell <rcampbell@...dia.com>
To:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
CC:     Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        Jason Gunthorpe <jgg@...lanox.com>,
        "Bharata B Rao" <bharata@...ux.ibm.com>,
        Michal Hocko <mhocko@...nel.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Ralph Campbell <rcampbell@...dia.com>
Subject: [PATCH 3/3] mm/migrate: add stable check in migrate_vma_insert_page()

migrate_vma_insert_page() closely follows the code in:
  __handle_mm_fault()
    handle_pte_fault()
      do_anonymous_page()

Add a call to check_stable_address_space() after locking the page table
entry before inserting a ZONE_DEVICE private zero page mapping similar to
page faulting a new anonymous page.

Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
---
 mm/migrate.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index 4b1a6d69afb5..403b82472d24 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -48,6 +48,7 @@
 #include <linux/page_owner.h>
 #include <linux/sched/mm.h>
 #include <linux/ptrace.h>
+#include <linux/oom.h>
 
 #include <asm/tlbflush.h>
 
@@ -2675,6 +2676,14 @@ int migrate_vma_setup(struct migrate_vma *args)
 }
 EXPORT_SYMBOL(migrate_vma_setup);
 
+/*
+ * This code closely matches the code in:
+ *   __handle_mm_fault()
+ *     handle_pte_fault()
+ *       do_anonymous_page()
+ * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
+ * private page.
+ */
 static void migrate_vma_insert_page(struct migrate_vma *migrate,
 				    unsigned long addr,
 				    struct page *page,
@@ -2755,6 +2764,9 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
 
 	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
 
+	if (check_stable_address_space(mm))
+		goto unlock_abort;
+
 	if (pte_present(*ptep)) {
 		unsigned long pfn = pte_pfn(*ptep);
 
-- 
2.20.1