mm/ZONE_DEVICE: special case put_page() for device private pages

A ZONE_DEVICE page that reach a refcount of 1 is free ie no longer have
any user.  For device private pages this is important to catch and thus we
need to special case put_page() for this.

Link: http://lkml.kernel.org/r/20170817000548.32038-9-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Sherry Cheung <SCheung@nvidia.com>
Cc: Subhash Gutti <sgutti@nvidia.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 8e164ec9eed0e34e8e1d6654fced5f9b64f97d5c..8aa6b82679e2381e6b60cd5a829fc370269bedb9 100644 (file)
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -126,6 +126,14 @@ struct dev_pagemap {
 void *devm_memremap_pages(struct device *dev, struct resource *res,
                struct percpu_ref *ref, struct vmem_altmap *altmap);
 struct dev_pagemap *find_dev_pagemap(resource_size_t phys);
+
+static inline bool is_zone_device_page(const struct page *page);
+
+static inline bool is_device_private_page(const struct page *page)
+{
+       return is_zone_device_page(page) &&
+               page->pgmap->type == MEMORY_DEVICE_PRIVATE;
+}
 #else
 static inline void *devm_memremap_pages(struct device *dev,
                struct resource *res, struct percpu_ref *ref,
@@ -144,6 +152,11 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
 {
        return NULL;
 }
+
+static inline bool is_device_private_page(const struct page *page)
+{
+       return false;
+}
 #endif
 
 /**

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a74c4e95435223e835510d80764ff33e52b06dfd..eccdab4bb44a5312cf5849379c445a34be3881ed 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -23,6 +23,7 @@
 #include <linux/page_ext.h>
 #include <linux/err.h>
 #include <linux/page_ref.h>
+#include <linux/memremap.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -792,25 +793,25 @@ static inline bool is_zone_device_page(const struct page *page)
 {
        return page_zonenum(page) == ZONE_DEVICE;
 }
-
-static inline bool is_device_private_page(const struct page *page)
-{
-       /* See MEMORY_DEVICE_PRIVATE in include/linux/memory_hotplug.h */
-       return ((page_zonenum(page) == ZONE_DEVICE) &&
-               (page->pgmap->type == MEMORY_DEVICE_PRIVATE));
-}
 #else
 static inline bool is_zone_device_page(const struct page *page)
 {
        return false;
 }
+#endif
 
-static inline bool is_device_private_page(const struct page *page)
+#ifdef CONFIG_DEVICE_PRIVATE
+void put_zone_device_private_page(struct page *page);
+#else
+static inline void put_zone_device_private_page(struct page *page)
 {
-       return false;
 }
 #endif
 
+static inline bool is_device_private_page(const struct page *page);
+
+DECLARE_STATIC_KEY_FALSE(device_private_key);
+
 static inline void get_page(struct page *page)
 {
        page = compound_head(page);
@@ -826,6 +827,18 @@ static inline void put_page(struct page *page)
 {
        page = compound_head(page);
 
+       /*
+        * For private device pages we need to catch refcount transition from
+        * 2 to 1, when refcount reach one it means the private device page is
+        * free and we need to inform the device driver through callback. See
+        * include/linux/memremap.h and HMM for details.
+        */
+       if (static_branch_unlikely(&device_private_key) &&
+           unlikely(is_device_private_page(page))) {
+               put_zone_device_private_page(page);
+               return;
+       }
+
        if (put_page_testzero(page))
                __put_page(page);
 }

diff --git a/kernel/memremap.c b/kernel/memremap.c
index f1d1e0dfe8b4f693db64668c46873a56ab8995d7..1403cf16fa61b617c4df0a9256fec664de0f0635 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -11,7 +11,6 @@
  * General Public License for more details.
  */
 #include <linux/radix-tree.h>
-#include <linux/memremap.h>
 #include <linux/device.h>
 #include <linux/types.h>
 #include <linux/pfn_t.h>
@@ -500,3 +499,27 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
        return pgmap ? pgmap->altmap : NULL;
 }
 #endif /* CONFIG_ZONE_DEVICE */
+
+
+#ifdef CONFIG_DEVICE_PRIVATE
+void put_zone_device_private_page(struct page *page)
+{
+       int count = page_ref_dec_return(page);
+
+       /*
+        * If refcount is 1 then page is freed and refcount is stable as nobody
+        * holds a reference on the page.
+        */
+       if (count == 1) {
+               /* Clear Active bit in case of parallel mark_page_accessed */
+               __ClearPageActive(page);
+               __ClearPageWaiters(page);
+
+               page->mapping = NULL;
+
+               page->pgmap->page_free(page, page->pgmap->data);
+       } else if (!count)
+               __put_page(page);
+}
+EXPORT_SYMBOL(put_zone_device_private_page);
+#endif /* CONFIG_DEVICE_PRIVATE */

diff --git a/mm/hmm.c b/mm/hmm.c
index f6c745b9a25ae1f4a31dd45fc5b9cb895832f48d..3c6265d4254b194791020b0a08efda588b7ffb4e 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -25,9 +25,17 @@
 #include <linux/sched.h>
 #include <linux/swapops.h>
 #include <linux/hugetlb.h>
+#include <linux/jump_label.h>
 #include <linux/mmu_notifier.h>
 
 
+/*
+ * Device private memory see HMM (Documentation/vm/hmm.txt) or hmm.h
+ */
+DEFINE_STATIC_KEY_FALSE(device_private_key);
+EXPORT_SYMBOL(device_private_key);
+
+
 #ifdef CONFIG_HMM
 static const struct mmu_notifier_ops hmm_mmu_notifier_ops;