+ mm-put_page-move-ref-decrement-to-put_zone_device_page.patch added to -mm tree

+ mm-put_page-move-ref-decrement-to-put_zone_device_page.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/put_page: move ref decrement to put_zone_device_page()
has been added to the -mm tree.  Its filename is
     mm-put_page-move-ref-decrement-to-put_zone_device_page.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-put_page-move-ref-decrement-to-put_zone_device_page.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-put_page-move-ref-decrement-to-put_zone_device_page.patch

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------------------------------------------------------
From: Jérôme Glisse <jglisse@redhat.com>
Subject: mm/put_page: move ref decrement to put_zone_device_page()

This does not affect non ZONE_DEVICE page.  In order to allow ZONE_DEVICE
page to be tracked we need to detect when refcount of a ZONE_DEVICE page
reach 1 (not 0 as non ZONE_DEVICE page).

This patch just move put_page_testzero() from put_page() to
put_zone_device_page() and only for ZONE_DEVICE.  It does not add any
overhead compare to existing code.

Link: http://lkml.kernel.org/r/1489680335-6594-3-git-send-email-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |    8 +++++---
 kernel/memremap.c  |    2 ++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff -puN include/linux/mm.h~mm-put_page-move-ref-decrement-to-put_zone_device_page include/linux/mm.h
--- a/include/linux/mm.h~mm-put_page-move-ref-decrement-to-put_zone_device_page
+++ a/include/linux/mm.h
@@ -795,11 +795,13 @@ static inline void put_page(struct page
 {
 	page = compound_head(page);
 
+	if (unlikely(is_zone_device_page(page))) {
+		put_zone_device_page(page);
+		return;
+	}
+
 	if (put_page_testzero(page))
 		__put_page(page);
-
-	if (unlikely(is_zone_device_page(page)))
-		put_zone_device_page(page);
 }
 
 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
diff -puN kernel/memremap.c~mm-put_page-move-ref-decrement-to-put_zone_device_page kernel/memremap.c
--- a/kernel/memremap.c~mm-put_page-move-ref-decrement-to-put_zone_device_page
+++ a/kernel/memremap.c
@@ -190,6 +190,8 @@ EXPORT_SYMBOL(get_zone_device_page);
 
 void put_zone_device_page(struct page *page)
 {
+	page_ref_dec(page);
+
 	put_dev_pagemap(page->pgmap);
 }
 EXPORT_SYMBOL(put_zone_device_page);
_

Patches currently in -mm which might be from jglisse@redhat.com are

mm-memory-hotplug-convert-device-bool-to-int-to-allow-for-more-flags-v3.patch
mm-put_page-move-ref-decrement-to-put_zone_device_page.patch
mm-zone_device-free-page-callback-when-page-is-freed-v3.patch
mm-zone_device-unaddressable-add-support-for-un-addressable-device-memory-v3.patch
mm-zone_device-x86-add-support-for-un-addressable-device-memory.patch
mm-migrate-add-new-boolean-copy-flag-to-migratepage-callback.patch
mm-migrate-new-memory-migration-helper-for-use-with-device-memory-v4.patch
mm-migrate-migrate_vma-unmap-page-from-vma-while-collecting-pages.patch
mm-hmm-heterogeneous-memory-management-hmm-for-short.patch
mm-hmm-mirror-mirror-process-address-space-on-device-with-hmm-helpers.patch
mm-hmm-mirror-helper-to-snapshot-cpu-page-table-v2.patch
mm-hmm-mirror-device-page-fault-handler.patch
mm-hmm-migrate-support-un-addressable-zone_device-page-in-migration.patch
mm-migrate-allow-migrate_vma-to-alloc-new-page-on-empty-entry.patch
mm-hmm-devmem-device-memory-hotplug-using-zone_device.patch
mm-hmm-devmem-dummy-hmm-device-for-zone_device-memory-v2.patch