[PATCH 13/15] mm, devmap: introduce CONFIG_DEVMAP_MANAGED_PAGES

From: Dan Williams
Date: Tue Oct 31 2017 - 19:29:16 EST

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Combine the now three use cases of page-idle callbacks for ZONE_DEVICE
memory into a common selectable symbol.

Cc: "JÃrÃme Glisse" <jglisse@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/dax/super.c | 2 ++
fs/Kconfig | 1 +
include/linux/memremap.h | 18 +++++++++++++++---
include/linux/mm.h | 46 ++++++++++++++++++++++++----------------------
kernel/memremap.c | 25 +++++++++++++++++++++----
mm/Kconfig | 5 +++++
mm/hmm.c | 13 ++-----------
mm/swap.c | 3 ++-
8 files changed, 72 insertions(+), 41 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 193e0cd8d90c..4ac359e14777 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -190,6 +190,7 @@ struct dax_device *fs_dax_claim_bdev(struct block_device *bdev, void *owner)
return NULL;
}

+ devmap_managed_pages_enable();
pgmap->type = MEMORY_DEVICE_FS_DAX;
pgmap->page_free = generic_dax_pagefree;
pgmap->data = owner;
@@ -214,6 +215,7 @@ void fs_dax_release(struct dax_device *dax_dev, void *owner)
pgmap->type = MEMORY_DEVICE_HOST;
pgmap->page_free = NULL;
pgmap->data = NULL;
+ devmap_managed_pages_disable();
mutex_unlock(&devmap_lock);
}
EXPORT_SYMBOL_GPL(fs_dax_release);
diff --git a/fs/Kconfig b/fs/Kconfig
index b40128bf6d1a..cd4ee17ecdd8 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -38,6 +38,7 @@ config FS_DAX
bool "Direct Access (DAX) support"
depends on MMU
depends on !(ARM || MIPS || SPARC)
+ select DEVMAP_MANAGED_PAGES
select FS_IOMAP
select DAX
help
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 39d2de3f744b..a6716f5335e7 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -1,6 +1,5 @@
#ifndef _LINUX_MEMREMAP_H_
#define _LINUX_MEMREMAP_H_
-#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/percpu-refcount.h>

@@ -138,6 +137,9 @@ struct dev_pagemap {
enum memory_type type;
};

+void devmap_managed_pages_enable(void);
+void devmap_managed_pages_disable(void);
+
#ifdef CONFIG_ZONE_DEVICE
void *devm_memremap_pages(struct device *dev, struct resource *res,
struct percpu_ref *ref, struct vmem_altmap *altmap);
@@ -164,7 +166,7 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
}
#endif

-#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
+#ifdef CONFIG_DEVMAP_MANAGED_PAGES
static inline bool is_device_private_page(const struct page *page)
{
return is_zone_device_page(page) &&
@@ -176,7 +178,17 @@ static inline bool is_device_public_page(const struct page *page)
return is_zone_device_page(page) &&
page->pgmap->type == MEMORY_DEVICE_PUBLIC;
}
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
+#else /* CONFIG_DEVMAP_MANAGED_PAGES */
+static inline bool is_device_private_page(const struct page *page)
+{
+ return false;
+}
+
+static inline bool is_device_public_page(const struct page *page)
+{
+ return false;
+}
+#endif /* CONFIG_DEVMAP_MANAGED_PAGES */

/**
* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8c1e3ac77285..2d6cf2583e10 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -800,27 +800,32 @@ static inline bool is_zone_device_page(const struct page *page)
}
#endif

-#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
-void put_zone_device_private_or_public_page(struct page *page);
-DECLARE_STATIC_KEY_FALSE(device_private_key);
-#define IS_HMM_ENABLED static_branch_unlikely(&device_private_key)
-static inline bool is_device_private_page(const struct page *page);
-static inline bool is_device_public_page(const struct page *page);
-#else /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
-static inline void put_zone_device_private_or_public_page(struct page *page)
-{
-}
-#define IS_HMM_ENABLED 0
-static inline bool is_device_private_page(const struct page *page)
+#ifdef CONFIG_DEVMAP_MANAGED_PAGES
+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)
{
+ if (!static_branch_unlikely(&devmap_managed_key))
+ return false;
+ if (!is_zone_device_page(page))
+ return false;
+ switch (page->pgmap->type) {
+ case MEMORY_DEVICE_PRIVATE:
+ case MEMORY_DEVICE_PUBLIC:
+ case MEMORY_DEVICE_FS_DAX:
+ __put_devmap_managed_page(page);
+ return true;
+ default:
+ break;
+ }
return false;
}
-static inline bool is_device_public_page(const struct page *page)
+#else /* CONFIG_DEVMAP_MANAGED_PAGES */
+static inline bool put_devmap_managed_page(struct page *page)
{
return false;
}
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
-
+#endif /* CONFIG_DEVMAP_MANAGED_PAGES */

static inline void get_page(struct page *page)
{
@@ -838,16 +843,13 @@ 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
+ * For devmap managed pages we need to catch refcount transition from
+ * 2 to 1, when refcount reach one it means the page is free and we
+ * need to inform the device driver through callback. See
* include/linux/memremap.h and HMM for details.
*/
- if (IS_HMM_ENABLED && unlikely(is_device_private_page(page) ||
- unlikely(is_device_public_page(page)))) {
- put_zone_device_private_or_public_page(page);
+ if (put_devmap_managed_page(page))
return;
- }

if (put_page_testzero(page))
__put_page(page);
diff --git a/kernel/memremap.c b/kernel/memremap.c
index bf61cfa89c7d..8a4ebfe9db4e 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -503,9 +503,26 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
}
#endif /* CONFIG_ZONE_DEVICE */

+#ifdef CONFIG_DEVMAP_MANAGED_PAGES
+DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
+EXPORT_SYMBOL(devmap_managed_key);
+static atomic_t devmap_enable;

-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
-void put_zone_device_private_or_public_page(struct page *page)
+void devmap_managed_pages_enable(void)
+{
+ if (atomic_inc_return(&devmap_enable) == 1)
+ static_branch_enable(&devmap_managed_key);
+}
+EXPORT_SYMBOL(devmap_managed_pages_enable);
+
+void devmap_managed_pages_disable(void)
+{
+ if (atomic_dec_and_test(&devmap_enable))
+ static_branch_disable(&devmap_managed_key);
+}
+EXPORT_SYMBOL(devmap_managed_pages_disable);
+
+void __put_devmap_managed_page(struct page *page)
{
int count = page_ref_dec_return(page);

@@ -525,5 +542,5 @@ void put_zone_device_private_or_public_page(struct page *page)
} else if (!count)
__put_page(page);
}
-EXPORT_SYMBOL(put_zone_device_private_or_public_page);
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
+EXPORT_SYMBOL(__put_devmap_managed_page);
+#endif /* CONFIG_DEVMAP_MANAGED_PAGES */
diff --git a/mm/Kconfig b/mm/Kconfig
index 9c4bdddd80c2..8ee95197dc9f 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -705,6 +705,9 @@ config ARCH_HAS_HMM
config MIGRATE_VMA_HELPER
bool

+config DEVMAP_MANAGED_PAGES
+ bool
+
config HMM
bool
select MIGRATE_VMA_HELPER
@@ -725,6 +728,7 @@ config DEVICE_PRIVATE
bool "Unaddressable device memory (GPU memory, ...)"
depends on ARCH_HAS_HMM
select HMM
+ select DEVMAP_MANAGED_PAGES

help
Allows creation of struct pages to represent unaddressable device
@@ -735,6 +739,7 @@ config DEVICE_PUBLIC
bool "Addressable device memory (like GPU memory)"
depends on ARCH_HAS_HMM
select HMM
+ select DEVMAP_MANAGED_PAGES

help
Allows creation of struct pages to represent addressable device
diff --git a/mm/hmm.c b/mm/hmm.c
index a88a847bccba..53c8f1dd821d 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -35,15 +35,6 @@

#define PA_SECTION_SIZE (1UL << PA_SECTION_SHIFT)

-#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
-/*
- * Device private memory see HMM (Documentation/vm/hmm.txt) or hmm.h
- */
-DEFINE_STATIC_KEY_FALSE(device_private_key);
-EXPORT_SYMBOL(device_private_key);
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
-
-
#if IS_ENABLED(CONFIG_HMM_MIRROR)
static const struct mmu_notifier_ops hmm_mmu_notifier_ops;

@@ -998,7 +989,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
resource_size_t addr;
int ret;

- static_branch_enable(&device_private_key);
+ devmap_managed_pages_enable();

devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
GFP_KERNEL, dev_to_node(device));
@@ -1092,7 +1083,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
return ERR_PTR(-EINVAL);

- static_branch_enable(&device_private_key);
+ devmap_managed_pages_enable();

devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
GFP_KERNEL, dev_to_node(device));
diff --git a/mm/swap.c b/mm/swap.c
index a77d68f2c1b6..09c71044b565 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -29,6 +29,7 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/backing-dev.h>
+#include <linux/memremap.h>
#include <linux/memcontrol.h>
#include <linux/gfp.h>
#include <linux/uio.h>
@@ -772,7 +773,7 @@ void release_pages(struct page **pages, int nr, bool cold)
flags);
locked_pgdat = NULL;
}
- put_zone_device_private_or_public_page(page);
+ put_devmap_managed_page(page);
continue;
}

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