In preparation for fixing dax-dma-vs-unmap issues, filesystems need to
be able to rely on the fact that they will get wakeups on dev_pagemap
page-idle events. Introduce MEMORY_DEVICE_FS_DAX and
generic_dax_page_free() as common indicator / infrastructure for dax
filesytems to require. With this change there are no users of the
MEMORY_DEVICE_HOST designation, so remove it.
The HMM sub-system extended dev_pagemap to arrange a callback when a
dev_pagemap managed page is freed. Since a dev_pagemap page is free /
idle when its reference count is 1 it requires an additional branch to
check the page-type at put_page() time. Given put_page() is a hot-path
we do not want to incur that check if HMM is not in use, so a static
branch is used to avoid that overhead when not necessary.
Now, the FS_DAX implementation wants to reuse this mechanism for
receiving dev_pagemap ->page_free() callbacks. Rework the HMM-specific
static-key into a generic mechanism that either HMM or FS_DAX code paths
can enable.
For ARCH=um builds, and any other arch that lacks ZONE_DEVICE support,
care must be taken to compile out the DEV_PAGEMAP_OPS infrastructure.
However, we still need to support FS_DAX in the FS_DAX_LIMITED case
implemented by the s390/dcssblk driver.
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Reported-by: Thomas Meyer <thomas@xxxxxxxx>
Reported-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
This patch replaces and consolidates patch 2 [1] and 4 [2] from the v9
series [3] for "dax: fix dma vs truncate/hole-punch".
The original implementation which introduced fs_dax_claim() was broken
in the presence of partitions as filesystems on partitions of a pmem
device would collide when attempting to issue fs_dax_claim().
Instead, since this new page wakeup behavior is a property of
dev_pagemap pages and there is a 1:1 relationship between a pmem device
and its dev_pagemap instance, make the pmem driver own the page wakeup
initialization rather than the filesystem.
This simplifies the implementation considerably. The diffstat for the
series is now:
21 files changed, 546 insertions(+), 277 deletions(-)
...down from:
24 files changed, 730 insertions(+), 297 deletions(-)
The other patches in the series are not included since they did not
change in any meaningful way. Let me know if anyone wants a full resend,
it will otherwise be available in -next shortly. Given the change in
approach I did not carry Reviewed-by tags from patch 2 and 4 to this
patch.
[1]: [PATCH v9 2/9] mm, dax: enable filesystems to trigger dev_pagemap ->page_free callbacks
https://lists.01.org/pipermail/linux-nvdimm/2018-April/015459.html
[2]: [PATCH v9 4/9] mm, dev_pagemap: introduce CONFIG_DEV_PAGEMAP_OPS
https://lists.01.org/pipermail/linux-nvdimm/2018-April/015461.html
[3]: [PATCH v9 0/9] dax: fix dma vs truncate/hole-punch
https://lists.01.org/pipermail/linux-nvdimm/2018-April/015457.html
drivers/dax/super.c | 18 ++++++++---
drivers/nvdimm/pfn_devs.c | 2 -
drivers/nvdimm/pmem.c | 20 +++++++++++++
fs/Kconfig | 1 +
include/linux/memremap.h | 41 ++++++++++----------------
include/linux/mm.h | 71 ++++++++++++++++++++++++++++++++++-----------
kernel/memremap.c | 37 +++++++++++++++++++++--
mm/Kconfig | 5 +++
mm/hmm.c | 13 +-------
mm/swap.c | 3 +-
10 files changed, 143 insertions(+), 68 deletions(-)
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 2b2332b605e4..4928b7fcfb71 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -134,15 +134,21 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
* on being able to do (page_address(pfn_to_page())).
*/
WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
+ return 0;
} else if (pfn_t_devmap(pfn)) {
- /* pass */;
- } else {
- pr_debug("VFS (%s): error: dax support not enabled\n",
- sb->s_id);
- return -EOPNOTSUPP;
+ struct dev_pagemap *pgmap;
+
+ pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
+ if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX) {
+ put_dev_pagemap(pgmap);
+ return 0;
+ }
+ put_dev_pagemap(pgmap);
}
- return 0;
+ pr_debug("VFS (%s): error: dax support not enabled\n",
+ sb->s_id);
+ return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(__bdev_dax_supported);
#endif
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 30b08791597d..3f7ad5bc443e 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -561,8 +561,6 @@ static int __nvdimm_setup_pfn(struct nd_pfn *nd_pfn, struct dev_pagemap *pgmap)
res->start += start_pad;
res->end -= end_trunc;
- pgmap->type = MEMORY_DEVICE_HOST;
-
if (nd_pfn->mode == PFN_MODE_RAM) {
if (offset < SZ_8K)
return -EINVAL;
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 9d714926ecf5..e6d94604e9a4 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -294,6 +294,22 @@ static void pmem_release_disk(void *__pmem)
put_disk(pmem->disk);
}
+static void pmem_release_pgmap_ops(void *__pgmap)
+{
+ dev_pagemap_put_ops();
+}
+
+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->page_free = generic_dax_pagefree;
+
+ return 0;
+}
+
static int pmem_attach_disk(struct device *dev,
struct nd_namespace_common *ndns)
{
@@ -353,6 +369,8 @@ 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;
addr = devm_memremap_pages(dev, &pmem->pgmap);
pfn_sb = nd_pfn->pfn_sb;
pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
@@ -364,6 +382,8 @@ 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;
addr = devm_memremap_pages(dev, &pmem->pgmap);
pmem->pfn_flags |= PFN_MAP;
memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
diff --git a/fs/Kconfig b/fs/Kconfig
index bc821a86d965..1e050e012eb9 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 DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED)
select FS_IOMAP
select DAX
help
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 7b4899c06f49..29ea63544c4d 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -1,7 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_MEMREMAP_H_
#define _LINUX_MEMREMAP_H_
-#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/percpu-refcount.h>
@@ -30,13 +29,6 @@ struct vmem_altmap {
* Specialize ZONE_DEVICE memory into multiple types each having differents
* usage.
*
- * MEMORY_DEVICE_HOST:
- * Persistent device memory (pmem): struct page might be allocated in different
- * memory and architecture might want to perform special actions. It is similar
- * to regular memory, in that the CPU can access it transparently. However,
- * it is likely to have different bandwidth and latency than regular memory.
- * See Documentation/nvdimm/nvdimm.txt for more information.
- *
* MEMORY_DEVICE_PRIVATE:
* Device memory that is not directly addressable by the CPU: CPU can neither
* read nor write private memory. In this case, we do still have struct pages
@@ -53,11 +45,19 @@ struct vmem_altmap {
* driver can hotplug the device memory using ZONE_DEVICE and with that memory
* type. Any page of a process can be migrated to such memory. However no one
* should be allow to pin such memory so that it can always be evicted.
+ *
+ * MEMORY_DEVICE_FS_DAX:
+ * Host memory that has similar access semantics as System RAM i.e. DMA
+ * coherent and supports page pinning. In support of coordinating page
+ * pinning vs other operations MEMORY_DEVICE_FS_DAX arranges for a
+ * wakeup event whenever a page is unpinned and becomes idle. This
+ * wakeup is used to coordinate physical address space management (ex:
+ * fs truncate/hole punch) vs pinned pages (ex: device dma).
*/
enum memory_type {
- MEMORY_DEVICE_HOST = 0,
- MEMORY_DEVICE_PRIVATE,
+ MEMORY_DEVICE_PRIVATE = 1,
MEMORY_DEVICE_PUBLIC,
+ MEMORY_DEVICE_FS_DAX,
};
/*
@@ -123,15 +123,18 @@ struct dev_pagemap {
};
#ifdef CONFIG_ZONE_DEVICE
+void generic_dax_pagefree(struct page *page, void *data);
void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
struct dev_pagemap *pgmap);
unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
-
-static inline bool is_zone_device_page(const struct page *page);
#else
+static inline void generic_dax_pagefree(struct page *page, void *data)
+{
+}
+
static inline void *devm_memremap_pages(struct device *dev,
struct dev_pagemap *pgmap)
{
@@ -161,20 +164,6 @@ static inline void vmem_altmap_free(struct vmem_altmap *altmap,
}
#endif /* CONFIG_ZONE_DEVICE */
-#if defined(CONFIG_DEVICE_PRIVATE) || defined(CONFIG_DEVICE_PUBLIC)
-static inline bool is_device_private_page(const struct page *page)
-{
- return is_zone_device_page(page) &&
- page->pgmap->type == MEMORY_DEVICE_PRIVATE;
-}
-
-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 */
-
static inline void put_dev_pagemap(struct dev_pagemap *pgmap)
{
if (pgmap)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1ac1f06a4be6..6e19265ee8f8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -821,27 +821,65 @@ 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)
+#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)
+{
+ 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_private_page(const struct page *page)
{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PRIVATE;
}
-#define IS_HMM_ENABLED 0
+
+static inline bool is_device_public_page(const struct page *page)
+{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PUBLIC;
+}
+
+#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;
+}
+
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_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
-
+#endif /* CONFIG_DEV_PAGEMAP_OPS */
static inline void get_page(struct page *page)
{
@@ -859,16 +897,13 @@ 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 37a9604133f6..3e546c6beb42 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -9,12 +9,19 @@
#include <linux/memory_hotplug.h>
#include <linux/swap.h>
#include <linux/swapops.h>
+#include <linux/wait_bit.h>
static DEFINE_MUTEX(pgmap_lock);
static RADIX_TREE(pgmap_radix, GFP_KERNEL);
#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
+void generic_dax_pagefree(struct page *page, void *data)
+{
+ wake_up_var(&page->_refcount);
+}
+EXPORT_SYMBOL_GPL(generic_dax_pagefree);
+
static unsigned long order_at(struct resource *res, unsigned long pgoff)
{
unsigned long phys_pgoff = PHYS_PFN(res->start) + pgoff;
@@ -301,8 +308,30 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
return pgmap;
}
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
-void put_zone_device_private_or_public_page(struct page *page)
+#ifdef CONFIG_DEV_PAGEMAP_OPS
+DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
+EXPORT_SYMBOL_GPL(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);
@@ -322,5 +351,5 @@ 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_GPL(__put_devmap_managed_page);
+#endif /* CONFIG_DEV_PAGEMAP_OPS */
diff --git a/mm/Kconfig b/mm/Kconfig
index d5004d82a1d6..bf9d6366bced 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -692,6 +692,9 @@ config ARCH_HAS_HMM
config MIGRATE_VMA_HELPER
bool
+config DEV_PAGEMAP_OPS
+ bool
+
config HMM
bool
select MIGRATE_VMA_HELPER
@@ -712,6 +715,7 @@ config DEVICE_PRIVATE
bool "Unaddressable device memory (GPU memory, ...)"
depends on ARCH_HAS_HMM
select HMM
+ select DEV_PAGEMAP_OPS
help
Allows creation of struct pages to represent unaddressable device
@@ -722,6 +726,7 @@ config DEVICE_PUBLIC
bool "Addressable device memory (like GPU memory)"
depends on ARCH_HAS_HMM
select HMM
+ select DEV_PAGEMAP_OPS
help
Allows creation of struct pages to represent addressable device
diff --git a/mm/hmm.c b/mm/hmm.c
index 486dc394a5a3..de7b6bf77201 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;
@@ -1167,7 +1158,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
resource_size_t addr;
int ret;
- static_branch_enable(&device_private_key);
+ dev_pagemap_get_ops();
devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
GFP_KERNEL, dev_to_node(device));
@@ -1261,7 +1252,7 @@ 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);
+ dev_pagemap_get_ops();
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 3dd518832096..26fc9b5f1b6c 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>
@@ -743,7 +744,7 @@ void release_pages(struct page **pages, int nr)
flags);
locked_pgdat = NULL;
}
- put_zone_device_private_or_public_page(page);
+ put_devmap_managed_page(page);
continue;
}
