Re: [Nouveau] [PATCH 09/22] memremap: lift the devmap_enable manipulation into devm_memremap_pages

2019-06-13 Thread Jason Gunthorpe 
On Thu, Jun 13, 2019 at 11:43:12AM +0200, Christoph Hellwig wrote:
> 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.
> diff --git a/mm/hmm.c b/mm/hmm.c
> index c76a1b5defda..6dc769feb2e1 100644
> +++ 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();
> -

Where was the matching dev_pagemap_put_ops() for this hmm case? This
is a bug fix too?

The nouveau driver is the only one to actually call this hmm function
and it does it as part of a probe function. 

Seems reasonable, however, in the unlikely event that it fails to init
'dmem' the driver will retain a dev_pagemap_get_ops until it unloads.
This imbalance doesn't seem worth worrying about.

Reviewed-by: Christoph Hellwig 

Jason
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[Nouveau] [PATCH 09/22] memremap: lift the devmap_enable manipulation into devm_memremap_pages

2019-06-13 Thread Christoph Hellwig 
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 
---
 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) {
+