Just check if there is a ->page_free operation set and take care of the
static key enable, as well as the put using device managed resources.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 drivers/nvdimm/pmem.c | 23 +++--------------
 include/linux/mm.h    | 10 --------
 kernel/memremap.c     | 59 +++++++++++++++++++++++++++----------------
 mm/hmm.c              |  2 --
 4 files changed, 41 insertions(+), 53 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index b9638c6553a1..66837eed6375 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -334,11 +334,6 @@ static void pmem_release_disk(void *__pmem)
        put_disk(pmem->disk);
 }
 
-static void pmem_release_pgmap_ops(void *__pgmap)
-{
-       dev_pagemap_put_ops();
-}
-
 static void pmem_fsdax_page_free(struct page *page, void *data)
 {
        wake_up_var(&page->_refcount);
@@ -353,16 +348,6 @@ static const struct dev_pagemap_ops 
pmem_legacy_pagemap_ops = {
        .kill                   = pmem_kill,
 };
 
-static int setup_pagemap_fsdax(struct device *dev, struct dev_pagemap *pgmap)
-{
-       dev_pagemap_get_ops();
-       if (devm_add_action_or_reset(dev, pmem_release_pgmap_ops, pgmap))
-               return -ENOMEM;
-       pgmap->type = MEMORY_DEVICE_FS_DAX;
-       pgmap->ops = &fsdax_pagemap_ops;
-       return 0;
-}
-
 static int pmem_attach_disk(struct device *dev,
                struct nd_namespace_common *ndns)
 {
@@ -421,8 +406,8 @@ static int pmem_attach_disk(struct device *dev,
        pmem->pfn_flags = PFN_DEV;
        pmem->pgmap.ref = &q->q_usage_counter;
        if (is_nd_pfn(dev)) {
-               if (setup_pagemap_fsdax(dev, &pmem->pgmap))
-                       return -ENOMEM;
+               pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
+               pmem->pgmap.ops = &fsdax_pagemap_ops;
                addr = devm_memremap_pages(dev, &pmem->pgmap);
                pfn_sb = nd_pfn->pfn_sb;
                pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
@@ -434,8 +419,8 @@ static int pmem_attach_disk(struct device *dev,
        } else if (pmem_should_map_pages(dev)) {
                memcpy(&pmem->pgmap.res, &nsio->res, sizeof(pmem->pgmap.res));
                pmem->pgmap.altmap_valid = false;
-               if (setup_pagemap_fsdax(dev, &pmem->pgmap))
-                       return -ENOMEM;
+               pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
+               pmem->pgmap.ops = &fsdax_pagemap_ops;
                addr = devm_memremap_pages(dev, &pmem->pgmap);
                pmem->pfn_flags |= PFN_MAP;
                memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..edcf2b821647 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -921,8 +921,6 @@ static inline bool is_zone_device_page(const struct page 
*page)
 #endif
 
 #ifdef CONFIG_DEV_PAGEMAP_OPS
-void dev_pagemap_get_ops(void);
-void dev_pagemap_put_ops(void);
 void __put_devmap_managed_page(struct page *page);
 DECLARE_STATIC_KEY_FALSE(devmap_managed_key);
 static inline bool put_devmap_managed_page(struct page *page)
@@ -969,14 +967,6 @@ static inline bool is_pci_p2pdma_page(const struct page 
*page)
 #endif /* CONFIG_PCI_P2PDMA */
 
 #else /* CONFIG_DEV_PAGEMAP_OPS */
-static inline void dev_pagemap_get_ops(void)
-{
-}
-
-static inline void dev_pagemap_put_ops(void)
-{
-}
-
 static inline bool put_devmap_managed_page(struct page *page)
 {
        return false;
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 94b830b6eca5..6a3183cac764 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -17,6 +17,37 @@ static DEFINE_XARRAY(pgmap_array);
 #define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
 #define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
 
+#ifdef CONFIG_DEV_PAGEMAP_OPS
+DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
+EXPORT_SYMBOL(devmap_managed_key);
+static atomic_t devmap_enable;
+
+static void dev_pagemap_put_ops(void *data)
+{
+       if (atomic_dec_and_test(&devmap_enable))
+               static_branch_disable(&devmap_managed_key);
+}
+
+/*
+ * Toggle the static key for ->page_free() callbacks when dev_pagemap
+ * pages go idle.
+ */
+static int dev_pagemap_enable(struct device *dev)
+{
+       if (atomic_inc_return(&devmap_enable) == 1)
+               static_branch_enable(&devmap_managed_key);
+
+       if (devm_add_action_or_reset(dev, dev_pagemap_put_ops, NULL))
+               return -ENOMEM;
+       return 0;
+}
+#else
+static inline int dev_pagemap_enable(struct device *dev)
+{
+       return 0;
+}
+#endif /* CONFIG_DEV_PAGEMAP_OPS */
+
 #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
 vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
                       unsigned long addr,
@@ -159,6 +190,12 @@ void *devm_memremap_pages(struct device *dev, struct 
dev_pagemap *pgmap)
        if (!pgmap->ref || !pgmap->ops || !pgmap->ops->kill)
                return ERR_PTR(-EINVAL);
 
+       if (pgmap->ops->page_free) {
+               error = dev_pagemap_enable(dev);
+               if (error)
+                       return ERR_PTR(error);
+       }
+
        align_start = res->start & ~(SECTION_SIZE - 1);
        align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
                - align_start;
@@ -316,28 +353,6 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 EXPORT_SYMBOL_GPL(get_dev_pagemap);
 
 #ifdef CONFIG_DEV_PAGEMAP_OPS
-DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
-EXPORT_SYMBOL(devmap_managed_key);
-static atomic_t devmap_enable;
-
-/*
- * Toggle the static key for ->page_free() callbacks when dev_pagemap
- * pages go idle.
- */
-void dev_pagemap_get_ops(void)
-{
-       if (atomic_inc_return(&devmap_enable) == 1)
-               static_branch_enable(&devmap_managed_key);
-}
-EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
-
-void dev_pagemap_put_ops(void)
-{
-       if (atomic_dec_and_test(&devmap_enable))
-               static_branch_disable(&devmap_managed_key);
-}
-EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
-
 void __put_devmap_managed_page(struct page *page)
 {
        int count = page_ref_dec_return(page);
diff --git a/mm/hmm.c b/mm/hmm.c
index c76a1b5defda..6dc769feb2e1 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1378,8 +1378,6 @@ struct hmm_devmem *hmm_devmem_add(const struct 
hmm_devmem_ops *ops,
        void *result;
        int ret;
 
-       dev_pagemap_get_ops();
-
        devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
        if (!devmem)
                return ERR_PTR(-ENOMEM);
-- 
2.20.1

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