[PATCH v5 0/7] mm: Merge hmm into devm_memremap_pages, mark GPL-only

[PATCH v5 0/7] mm: Merge hmm into devm_memremap_pages, mark GPL-only

[Dan Williams]

Changes since v4 [1]:
* Rebase on v4.19-rc3
* Update changelogs and cover letter

[1]: https://lkml.org/lkml/2018/7/11/14

---

Hi Andrew,

Back from vacation and this series is still top of mind.
devm_memremap_pages() is a facility that can create struct page entries
for any arbitrary range and give drivers the ability to subvert core
aspects of page management. It, and anything derived from it (e.g. hmm,
pcip2p, etc...), is an EXPORT_SYMBOL_GPL() interface.

I see that commit 31c5bda3a656 "mm: fix exports that inadvertently make
put_page() EXPORT_SYMBOL_GPL" was merged ahead of this series to relieve
some of the pressure from innocent consumers of put_page(), but now we
need this series to address *producers* of device pages.

More details and justification in the changelogs. The 0day
infrastructure has reported success across 182 configs and this survives
the libnvdimm unit test suite. Aside from the controversial bits the
diffstat is compelling at:

    7 files changed, 138 insertions(+), 328 deletions(-).

Note that the series has some minor collisions with Alex's recent series
to improve devm_memremap_pages() scalability [2]. So, whichever you take
first the other will need a minor rebase.

[2]: https://www.lkml.org/lkml/2018/9/11/10

---

Dan Williams (7):
      mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL
      mm, devm_memremap_pages: Kill mapping "System RAM" support
      mm, devm_memremap_pages: Fix shutdown handling
      mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support
      mm, hmm: Use devm semantics for hmm_devmem_{add,remove}
      mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()
      mm, hmm: Mark hmm_devmem_{add,add_resource} EXPORT_SYMBOL_GPL


 drivers/dax/pmem.c                |   15 --
 drivers/nvdimm/pmem.c             |   18 +-
 include/linux/hmm.h               |    4 
 include/linux/memremap.h          |    7 +
 kernel/memremap.c                 |   98 ++++++++----
 mm/hmm.c                          |  303 +++++--------------------------------
 tools/testing/nvdimm/test/iomap.c |   21 ++-
 7 files changed, 138 insertions(+), 328 deletions(-)

[PATCH v5 1/7] mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL

[Dan Williams]

devm_memremap_pages() is a facility that can create struct page entries
for any arbitrary range and give drivers the ability to subvert core
aspects of page management.

Specifically the facility is tightly integrated with the kernel's memory
hotplug functionality. It injects an altmap argument deep into the
architecture specific vmemmap implementation to allow allocating from
specific reserved pages, and it has Linux specific assumptions about
page structure reference counting relative to get_user_pages() and
get_user_pages_fast(). It was an oversight and a mistake that this was
not marked EXPORT_SYMBOL_GPL from the outset.

Again, devm_memremap_pagex() exposes and relies upon core kernel
internal assumptions and will continue to evolve along with 'struct
page', memory hotplug, and support for new memory types / topologies.
Only an in-kernel GPL-only driver is expected to keep up with this
ongoing evolution. This interface, and functionality derived from this
interface, is not suitable for kernel-external drivers.

Cc: Michal Hocko <mhocko@suse.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 5b8600d39931..f95c7833db6d 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -283,7 +283,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	pgmap_radix_release(res, pgoff);
 	return ERR_PTR(error);
 }
-EXPORT_SYMBOL(devm_memremap_pages);
+EXPORT_SYMBOL_GPL(devm_memremap_pages);
 
 unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
 {

[PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Dan Williams]

Given the fact that devm_memremap_pages() requires a percpu_ref that is
torn down by devm_memremap_pages_release() the current support for
mapping RAM is broken.

Support for remapping "System RAM" has been broken since the beginning
and there is no existing user of this this code path, so just kill the
support and make it an explicit error.

This cleanup also simplifies a follow-on patch to fix the error path
when setting a devm release action for devm_memremap_pages_release()
fails.

Cc: Christoph Hellwig <hch@lst.de>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index f95c7833db6d..92e838127767 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -202,15 +202,12 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	is_ram = region_intersects(align_start, align_size,
 		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
 
-	if (is_ram == REGION_MIXED) {
-		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
-				__func__, res);
+	if (is_ram != REGION_DISJOINT) {
+		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
+				is_ram == REGION_MIXED ? "mixed" : "ram", res);
 		return ERR_PTR(-ENXIO);
 	}
 
-	if (is_ram == REGION_INTERSECTS)
-		return __va(res->start);
-
 	if (!pgmap->ref)
 		return ERR_PTR(-EINVAL);
 

[PATCH v5 3/7] mm, devm_memremap_pages: Fix shutdown handling

[Dan Williams]

The last step before devm_memremap_pages() returns success is to
allocate a release action, devm_memremap_pages_release(), to tear the
entire setup down. However, the result from devm_add_action() is not
checked.

Checking the error from devm_add_action() is not enough. The api
currently relies on the fact that the percpu_ref it is using is killed
by the time the devm_memremap_pages_release() is run. Rather than
continue this awkward situation, offload the responsibility of killing
the percpu_ref to devm_memremap_pages_release() directly. This allows
devm_memremap_pages() to do the right thing  relative to init failures
and shutdown.

Without this change we could fail to register the teardown of
devm_memremap_pages(). The likelihood of hitting this failure is tiny as
small memory allocations almost always succeed. However, the impact of
the failure is large given any future reconfiguration, or
disable/enable, of an nvdimm namespace will fail forever as subsequent
calls to devm_memremap_pages() will fail to setup the pgmap_radix since
there will be stale entries for the physical address range.

An argument could be made to require that the ->kill() operation be set
in the @pgmap arg rather than passed in separately. However, it helps
code readability, tracking the lifetime of a given instance, to be able
to grep the kill routine directly at the devm_memremap_pages() call
site.

Cc: <stable@vger.kernel.org>
Fixes: e8d513483300 ("memremap: change devm_memremap_pages interface...")
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/pmem.c                |   15 +++------------
 drivers/nvdimm/pmem.c             |   18 ++++++++----------
 include/linux/memremap.h          |    7 +++++--
 kernel/memremap.c                 |   36 +++++++++++++++++++-----------------
 tools/testing/nvdimm/test/iomap.c |   21 ++++++++++++++++++---
 5 files changed, 53 insertions(+), 44 deletions(-)

diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index 99e2aace8078..c1e03d769e6d 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -48,9 +48,8 @@ static void dax_pmem_percpu_exit(void *data)
 	percpu_ref_exit(ref);
 }
 
-static void dax_pmem_percpu_kill(void *data)
+static void dax_pmem_percpu_kill(struct percpu_ref *ref)
 {
-	struct percpu_ref *ref = data;
 	struct dax_pmem *dax_pmem = to_dax_pmem(ref);
 
 	dev_dbg(dax_pmem->dev, "trace\n");
@@ -112,17 +111,9 @@ static int dax_pmem_probe(struct device *dev)
 	}
 
 	dax_pmem->pgmap.ref = &dax_pmem->ref;
-	addr = devm_memremap_pages(dev, &dax_pmem->pgmap);
-	if (IS_ERR(addr)) {
-		devm_remove_action(dev, dax_pmem_percpu_exit, &dax_pmem->ref);
-		percpu_ref_exit(&dax_pmem->ref);
+	addr = devm_memremap_pages(dev, &dax_pmem->pgmap, dax_pmem_percpu_kill);
+	if (IS_ERR(addr))
 		return PTR_ERR(addr);
-	}
-
-	rc = devm_add_action_or_reset(dev, dax_pmem_percpu_kill,
-							&dax_pmem->ref);
-	if (rc)
-		return rc;
 
 	/* adjust the dax_region resource to the start of data */
 	memcpy(&res, &dax_pmem->pgmap.res, sizeof(res));
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 6071e2942053..c9cad5ebea5b 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -309,8 +309,11 @@ static void pmem_release_queue(void *q)
 	blk_cleanup_queue(q);
 }
 
-static void pmem_freeze_queue(void *q)
+static void pmem_freeze_queue(struct percpu_ref *ref)
 {
+	struct request_queue *q;
+
+	q = container_of(ref, typeof(*q), q_usage_counter);
 	blk_freeze_queue_start(q);
 }
 
@@ -405,7 +408,8 @@ static int pmem_attach_disk(struct device *dev,
 	if (is_nd_pfn(dev)) {
 		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
 			return -ENOMEM;
-		addr = devm_memremap_pages(dev, &pmem->pgmap);
+		addr = devm_memremap_pages(dev, &pmem->pgmap,
+				pmem_freeze_queue);
 		pfn_sb = nd_pfn->pfn_sb;
 		pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
 		pmem->pfn_pad = resource_size(res) -
@@ -418,20 +422,14 @@ static int pmem_attach_disk(struct device *dev,
 		pmem->pgmap.altmap_valid = false;
 		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
 			return -ENOMEM;
-		addr = devm_memremap_pages(dev, &pmem->pgmap);
+		addr = devm_memremap_pages(dev, &pmem->pgmap,
+				pmem_freeze_queue);
 		pmem->pfn_flags |= PFN_MAP;
 		memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
 	} else
 		addr = devm_memremap(dev, pmem->phys_addr,
 				pmem->size, ARCH_MEMREMAP_PMEM);
 
-	/*
-	 * At release time the queue must be frozen before
-	 * devm_memremap_pages is unwound
-	 */
-	if (devm_add_action_or_reset(dev, pmem_freeze_queue, q))
-		return -ENOMEM;
-
 	if (IS_ERR(addr))
 		return PTR_ERR(addr);
 	pmem->virt_addr = addr;
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index f91f9e763557..71f5e7c7dfb9 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -106,6 +106,7 @@ typedef void (*dev_page_free_t)(struct page *page, void *data);
  * @altmap: pre-allocated/reserved memory for vmemmap allocations
  * @res: physical address range covered by @ref
  * @ref: reference count that pins the devm_memremap_pages() mapping
+ * @kill: callback to transition @ref to the dead state
  * @dev: host device of the mapping for debug
  * @data: private data pointer for page_free()
  * @type: memory type: see MEMORY_* in memory_hotplug.h
@@ -117,13 +118,15 @@ struct dev_pagemap {
 	bool altmap_valid;
 	struct resource res;
 	struct percpu_ref *ref;
+	void (*kill)(struct percpu_ref *ref);
 	struct device *dev;
 	void *data;
 	enum memory_type type;
 };
 
 #ifdef CONFIG_ZONE_DEVICE
-void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
+void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
+		void (*kill)(struct percpu_ref *));
 struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 		struct dev_pagemap *pgmap);
 
@@ -131,7 +134,7 @@ unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
 void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
 #else
 static inline void *devm_memremap_pages(struct device *dev,
-		struct dev_pagemap *pgmap)
+		struct dev_pagemap *pgmap, void (*kill)(struct percpu_ref *))
 {
 	/*
 	 * Fail attempts to call devm_memremap_pages() without
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 92e838127767..ab5eb570d28d 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -122,14 +122,10 @@ static void devm_memremap_pages_release(void *data)
 	resource_size_t align_start, align_size;
 	unsigned long pfn;
 
+	pgmap->kill(pgmap->ref);
 	for_each_device_pfn(pfn, pgmap)
 		put_page(pfn_to_page(pfn));
 
-	if (percpu_ref_tryget_live(pgmap->ref)) {
-		dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
-		percpu_ref_put(pgmap->ref);
-	}
-
 	/* pages are dead and unused, undo the arch mapping */
 	align_start = res->start & ~(SECTION_SIZE - 1);
 	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
@@ -150,7 +146,8 @@ static void devm_memremap_pages_release(void *data)
 /**
  * devm_memremap_pages - remap and provide memmap backing for the given resource
  * @dev: hosting device for @res
- * @pgmap: pointer to a struct dev_pgmap
+ * @pgmap: pointer to a struct dev_pagemap
+ * @kill: routine to kill @pgmap->ref
  *
  * Notes:
  * 1/ At a minimum the res, ref and type members of @pgmap must be initialized
@@ -159,17 +156,15 @@ static void devm_memremap_pages_release(void *data)
  * 2/ The altmap field may optionally be initialized, in which case altmap_valid
  *    must be set to true
  *
- * 3/ pgmap.ref must be 'live' on entry and 'dead' before devm_memunmap_pages()
- *    time (or devm release event). The expected order of events is that ref has
- *    been through percpu_ref_kill() before devm_memremap_pages_release(). The
- *    wait for the completion of all references being dropped and
- *    percpu_ref_exit() must occur after devm_memremap_pages_release().
+ * 3/ pgmap->ref must be 'live' on entry and will be killed at
+ *    devm_memremap_pages_release() time, or if this routine fails.
  *
  * 4/ res is expected to be a host memory range that could feasibly be
  *    treated as a "System RAM" range, i.e. not a device mmio range, but
  *    this is not enforced.
  */
-void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
+void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
+		void (*kill)(struct percpu_ref *))
 {
 	resource_size_t align_start, align_size, align_end;
 	struct vmem_altmap *altmap = pgmap->altmap_valid ?
@@ -180,6 +175,9 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	int error, nid, is_ram;
 	struct dev_pagemap *conflict_pgmap;
 
+	if (!pgmap->ref || !kill)
+		return ERR_PTR(-EINVAL);
+
 	align_start = res->start & ~(SECTION_SIZE - 1);
 	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
 		- align_start;
@@ -205,12 +203,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	if (is_ram != REGION_DISJOINT) {
 		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
 				is_ram == REGION_MIXED ? "mixed" : "ram", res);
-		return ERR_PTR(-ENXIO);
+		error = -ENXIO;
+		goto err_init;
 	}
 
-	if (!pgmap->ref)
-		return ERR_PTR(-EINVAL);
-
 	pgmap->dev = dev;
 
 	mutex_lock(&pgmap_lock);
@@ -267,7 +263,11 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 		percpu_ref_get(pgmap->ref);
 	}
 
-	devm_add_action(dev, devm_memremap_pages_release, pgmap);
+	pgmap->kill = kill;
+	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
+			pgmap);
+	if (error)
+		return ERR_PTR(error);
 
 	return __va(res->start);
 
@@ -278,6 +278,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
  err_pfn_remap:
  err_radix:
 	pgmap_radix_release(res, pgoff);
+ err_init:
+	kill(pgmap->ref);
 	return ERR_PTR(error);
 }
 EXPORT_SYMBOL_GPL(devm_memremap_pages);
diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
index ff9d3a5825e1..ad544e6476a9 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -104,14 +104,29 @@ void *__wrap_devm_memremap(struct device *dev, resource_size_t offset,
 }
 EXPORT_SYMBOL(__wrap_devm_memremap);
 
-void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
+static void nfit_test_kill(void *_pgmap)
+{
+	struct dev_pagemap *pgmap = _pgmap;
+
+	pgmap->kill(pgmap->ref);
+}
+
+void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
+		void (*kill)(struct percpu_ref *))
 {
 	resource_size_t offset = pgmap->res.start;
 	struct nfit_test_resource *nfit_res = get_nfit_res(offset);
 
-	if (nfit_res)
+	if (nfit_res) {
+		int rc;
+
+		pgmap->kill = kill;
+		rc = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
+		if (rc)
+			return ERR_PTR(rc);
 		return nfit_res->buf + offset - nfit_res->res.start;
-	return devm_memremap_pages(dev, pgmap);
+	}
+	return devm_memremap_pages(dev, pgmap, kill);
 }
 EXPORT_SYMBOL(__wrap_devm_memremap_pages);
 

[PATCH v5 4/7] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support

[Dan Williams]

In preparation for consolidating all ZONE_DEVICE enabling via
devm_memremap_pages(), teach it how to handle the constraints of
MEMORY_DEVICE_PRIVATE ranges.

Cc: Christoph Hellwig <hch@lst.de>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c |   51 +++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 39 insertions(+), 12 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index ab5eb570d28d..3234a771e63a 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -132,9 +132,15 @@ static void devm_memremap_pages_release(void *data)
 		- align_start;
 
 	mem_hotplug_begin();
-	arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
-			&pgmap->altmap : NULL);
-	kasan_remove_zero_shadow(__va(align_start), align_size);
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		pfn = align_start >> PAGE_SHIFT;
+		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
+				align_size >> PAGE_SHIFT, NULL);
+	} else {
+		arch_remove_memory(align_start, align_size,
+				pgmap->altmap_valid ? &pgmap->altmap : NULL);
+		kasan_remove_zero_shadow(__va(align_start), align_size);
+	}
 	mem_hotplug_done();
 
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
@@ -234,17 +240,38 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
 		goto err_pfn_remap;
 
 	mem_hotplug_begin();
-	error = kasan_add_zero_shadow(__va(align_start), align_size);
-	if (error) {
-		mem_hotplug_done();
-		goto err_kasan;
-	}
 
-	error = arch_add_memory(nid, align_start, align_size, altmap, false);
-	if (!error)
-		move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
-					align_start >> PAGE_SHIFT,
+	/*
+	 * For device private memory we call add_pages() as we only need to
+	 * allocate and initialize struct page for the device memory. More-
+	 * over the device memory is un-accessible thus we do not want to
+	 * create a linear mapping for the memory like arch_add_memory()
+	 * would do.
+	 *
+	 * For all other device memory types, which are accessible by
+	 * the CPU, we do want the linear mapping and thus use
+	 * arch_add_memory().
+	 */
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		error = add_pages(nid, align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT, NULL, false);
+	} else {
+		struct zone *zone;
+
+		error = kasan_add_zero_shadow(__va(align_start), align_size);
+		if (error) {
+			mem_hotplug_done();
+			goto err_kasan;
+		}
+
+		error = arch_add_memory(nid, align_start, align_size, altmap,
+				false);
+		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
+		if (!error)
+			move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
 					align_size >> PAGE_SHIFT, altmap);
+	}
+
 	mem_hotplug_done();
 	if (error)
 		goto err_add_memory;

[PATCH v5 5/7] mm, hmm: Use devm semantics for hmm_devmem_{add, remove}

[Dan Williams]

devm semantics arrange for resources to be torn down when
device-driver-probe fails or when device-driver-release completes.
Similar to devm_memremap_pages() there is no need to support an explicit
remove operation when the users properly adhere to devm semantics.

Note that devm_kzalloc() automatically handles allocating node-local
memory.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 include/linux/hmm.h |    4 --
 mm/hmm.c            |  127 ++++++++++-----------------------------------------
 2 files changed, 25 insertions(+), 106 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 4c92e3ba3e16..5ec8635f602c 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -499,8 +499,7 @@ struct hmm_devmem {
  * enough and allocate struct page for it.
  *
  * The device driver can wrap the hmm_devmem struct inside a private device
- * driver struct. The device driver must call hmm_devmem_remove() before the
- * device goes away and before freeing the hmm_devmem struct memory.
+ * driver struct.
  */
 struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 				  struct device *device,
@@ -508,7 +507,6 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 					   struct device *device,
 					   struct resource *res);
-void hmm_devmem_remove(struct hmm_devmem *devmem);
 
 /*
  * hmm_devmem_page_set_drvdata - set per-page driver data field
diff --git a/mm/hmm.c b/mm/hmm.c
index c968e49f7a0c..ec1d9eccf176 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -939,7 +939,6 @@ static void hmm_devmem_ref_exit(void *data)
 
 	devmem = container_of(ref, struct hmm_devmem, ref);
 	percpu_ref_exit(ref);
-	devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
 }
 
 static void hmm_devmem_ref_kill(void *data)
@@ -950,7 +949,6 @@ static void hmm_devmem_ref_kill(void *data)
 	devmem = container_of(ref, struct hmm_devmem, ref);
 	percpu_ref_kill(ref);
 	wait_for_completion(&devmem->completion);
-	devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
 }
 
 static int hmm_devmem_fault(struct vm_area_struct *vma,
@@ -988,7 +986,7 @@ static void hmm_devmem_radix_release(struct resource *resource)
 	mutex_unlock(&hmm_devmem_lock);
 }
 
-static void hmm_devmem_release(struct device *dev, void *data)
+static void hmm_devmem_release(void *data)
 {
 	struct hmm_devmem *devmem = data;
 	struct resource *resource = devmem->resource;
@@ -996,11 +994,6 @@ static void hmm_devmem_release(struct device *dev, void *data)
 	struct zone *zone;
 	struct page *page;
 
-	if (percpu_ref_tryget_live(&devmem->ref)) {
-		dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
-		percpu_ref_put(&devmem->ref);
-	}
-
 	/* pages are dead and unused, undo the arch mapping */
 	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
 	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
@@ -1124,19 +1117,6 @@ static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
 	return ret;
 }
 
-static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
-{
-	struct hmm_devmem *devmem = data;
-
-	return devmem->resource == match_data;
-}
-
-static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
-{
-	devres_release(devmem->device, &hmm_devmem_release,
-		       &hmm_devmem_match, devmem->resource);
-}
-
 /*
  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
  *
@@ -1164,8 +1144,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 
 	dev_pagemap_get_ops();
 
-	devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
-				   GFP_KERNEL, dev_to_node(device));
+	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
 	if (!devmem)
 		return ERR_PTR(-ENOMEM);
 
@@ -1179,11 +1158,11 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
 			      0, GFP_KERNEL);
 	if (ret)
-		goto error_percpu_ref;
+		return ERR_PTR(ret);
 
-	ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
+	ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref);
 	if (ret)
-		goto error_devm_add_action;
+		return ERR_PTR(ret);
 
 	size = ALIGN(size, PA_SECTION_SIZE);
 	addr = min((unsigned long)iomem_resource.end,
@@ -1203,16 +1182,12 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 
 		devmem->resource = devm_request_mem_region(device, addr, size,
 							   dev_name(device));
-		if (!devmem->resource) {
-			ret = -ENOMEM;
-			goto error_no_resource;
-		}
+		if (!devmem->resource)
+			return ERR_PTR(-ENOMEM);
 		break;
 	}
-	if (!devmem->resource) {
-		ret = -ERANGE;
-		goto error_no_resource;
-	}
+	if (!devmem->resource)
+		return ERR_PTR(-ERANGE);
 
 	devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
 	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
@@ -1221,28 +1196,13 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 
 	ret = hmm_devmem_pages_create(devmem);
 	if (ret)
-		goto error_pages;
-
-	devres_add(device, devmem);
+		return ERR_PTR(ret);
 
-	ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
-	if (ret) {
-		hmm_devmem_remove(devmem);
+	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
+	if (ret)
 		return ERR_PTR(ret);
-	}
 
 	return devmem;
-
-error_pages:
-	devm_release_mem_region(device, devmem->resource->start,
-				resource_size(devmem->resource));
-error_no_resource:
-error_devm_add_action:
-	hmm_devmem_ref_kill(&devmem->ref);
-	hmm_devmem_ref_exit(&devmem->ref);
-error_percpu_ref:
-	devres_free(devmem);
-	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(hmm_devmem_add);
 
@@ -1258,8 +1218,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 
 	dev_pagemap_get_ops();
 
-	devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
-				   GFP_KERNEL, dev_to_node(device));
+	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
 	if (!devmem)
 		return ERR_PTR(-ENOMEM);
 
@@ -1273,12 +1232,12 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
 			      0, GFP_KERNEL);
 	if (ret)
-		goto error_percpu_ref;
+		return ERR_PTR(ret);
 
-	ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
+	ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit,
+			&devmem->ref);
 	if (ret)
-		goto error_devm_add_action;
-
+		return ERR_PTR(ret);
 
 	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
 	devmem->pfn_last = devmem->pfn_first +
@@ -1286,59 +1245,21 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 
 	ret = hmm_devmem_pages_create(devmem);
 	if (ret)
-		goto error_devm_add_action;
+		return ERR_PTR(ret);
 
-	devres_add(device, devmem);
+	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
+	if (ret)
+		return ERR_PTR(ret);
 
-	ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
-	if (ret) {
-		hmm_devmem_remove(devmem);
+	ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
+			&devmem->ref);
+	if (ret)
 		return ERR_PTR(ret);
-	}
 
 	return devmem;
-
-error_devm_add_action:
-	hmm_devmem_ref_kill(&devmem->ref);
-	hmm_devmem_ref_exit(&devmem->ref);
-error_percpu_ref:
-	devres_free(devmem);
-	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(hmm_devmem_add_resource);
 
-/*
- * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
- *
- * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
- *
- * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
- * of the device driver. It will free struct page and remove the resource that
- * reserved the physical address range for this device memory.
- */
-void hmm_devmem_remove(struct hmm_devmem *devmem)
-{
-	resource_size_t start, size;
-	struct device *device;
-	bool cdm = false;
-
-	if (!devmem)
-		return;
-
-	device = devmem->device;
-	start = devmem->resource->start;
-	size = resource_size(devmem->resource);
-
-	cdm = devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY;
-	hmm_devmem_ref_kill(&devmem->ref);
-	hmm_devmem_ref_exit(&devmem->ref);
-	hmm_devmem_pages_remove(devmem);
-
-	if (!cdm)
-		devm_release_mem_region(device, start, size);
-}
-EXPORT_SYMBOL(hmm_devmem_remove);
-
 /*
  * A device driver that wants to handle multiple devices memory through a
  * single fake device can use hmm_device to do so. This is purely a helper

[PATCH v5 6/7] mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()

[Dan Williams]

Commit e8d513483300 "memremap: change devm_memremap_pages interface to
use struct dev_pagemap" refactored devm_memremap_pages() to allow a
dev_pagemap instance to be supplied. Passing in a dev_pagemap interface
simplifies the design of pgmap type drivers in that they can rely on
container_of() to lookup any private data associated with the given
dev_pagemap instance.

In addition to the cleanups this also gives hmm users multi-order-radix
improvements that arrived with commit ab1b597ee0e4 "mm,
devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups"

As part of the conversion to the devm_memremap_pages() method of
handling the percpu_ref relative to when pages are put, the percpu_ref
completion needs to move to hmm_devmem_ref_exit(). See commit
71389703839e ("mm, zone_device: Replace {get, put}_zone_device_page...")
for details.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 mm/hmm.c |  194 ++++++++------------------------------------------------------
 1 file changed, 26 insertions(+), 168 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index ec1d9eccf176..c6cab5205b99 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -938,17 +938,16 @@ static void hmm_devmem_ref_exit(void *data)
 	struct hmm_devmem *devmem;
 
 	devmem = container_of(ref, struct hmm_devmem, ref);
+	wait_for_completion(&devmem->completion);
 	percpu_ref_exit(ref);
 }
 
-static void hmm_devmem_ref_kill(void *data)
+static void hmm_devmem_ref_kill(struct percpu_ref *ref)
 {
-	struct percpu_ref *ref = data;
 	struct hmm_devmem *devmem;
 
 	devmem = container_of(ref, struct hmm_devmem, ref);
 	percpu_ref_kill(ref);
-	wait_for_completion(&devmem->completion);
 }
 
 static int hmm_devmem_fault(struct vm_area_struct *vma,
@@ -971,152 +970,6 @@ static void hmm_devmem_free(struct page *page, void *data)
 	devmem->ops->free(devmem, page);
 }
 
-static DEFINE_MUTEX(hmm_devmem_lock);
-static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
-
-static void hmm_devmem_radix_release(struct resource *resource)
-{
-	resource_size_t key;
-
-	mutex_lock(&hmm_devmem_lock);
-	for (key = resource->start;
-	     key <= resource->end;
-	     key += PA_SECTION_SIZE)
-		radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
-	mutex_unlock(&hmm_devmem_lock);
-}
-
-static void hmm_devmem_release(void *data)
-{
-	struct hmm_devmem *devmem = data;
-	struct resource *resource = devmem->resource;
-	unsigned long start_pfn, npages;
-	struct zone *zone;
-	struct page *page;
-
-	/* pages are dead and unused, undo the arch mapping */
-	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
-	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
-
-	page = pfn_to_page(start_pfn);
-	zone = page_zone(page);
-
-	mem_hotplug_begin();
-	if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
-		__remove_pages(zone, start_pfn, npages, NULL);
-	else
-		arch_remove_memory(start_pfn << PAGE_SHIFT,
-				   npages << PAGE_SHIFT, NULL);
-	mem_hotplug_done();
-
-	hmm_devmem_radix_release(resource);
-}
-
-static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
-{
-	resource_size_t key, align_start, align_size, align_end;
-	struct device *device = devmem->device;
-	int ret, nid, is_ram;
-	unsigned long pfn;
-
-	align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
-	align_size = ALIGN(devmem->resource->start +
-			   resource_size(devmem->resource),
-			   PA_SECTION_SIZE) - align_start;
-
-	is_ram = region_intersects(align_start, align_size,
-				   IORESOURCE_SYSTEM_RAM,
-				   IORES_DESC_NONE);
-	if (is_ram == REGION_MIXED) {
-		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
-				__func__, devmem->resource);
-		return -ENXIO;
-	}
-	if (is_ram == REGION_INTERSECTS)
-		return -ENXIO;
-
-	if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
-		devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
-	else
-		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-
-	devmem->pagemap.res = *devmem->resource;
-	devmem->pagemap.page_fault = hmm_devmem_fault;
-	devmem->pagemap.page_free = hmm_devmem_free;
-	devmem->pagemap.dev = devmem->device;
-	devmem->pagemap.ref = &devmem->ref;
-	devmem->pagemap.data = devmem;
-
-	mutex_lock(&hmm_devmem_lock);
-	align_end = align_start + align_size - 1;
-	for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
-		struct hmm_devmem *dup;
-
-		dup = radix_tree_lookup(&hmm_devmem_radix,
-					key >> PA_SECTION_SHIFT);
-		if (dup) {
-			dev_err(device, "%s: collides with mapping for %s\n",
-				__func__, dev_name(dup->device));
-			mutex_unlock(&hmm_devmem_lock);
-			ret = -EBUSY;
-			goto error;
-		}
-		ret = radix_tree_insert(&hmm_devmem_radix,
-					key >> PA_SECTION_SHIFT,
-					devmem);
-		if (ret) {
-			dev_err(device, "%s: failed: %d\n", __func__, ret);
-			mutex_unlock(&hmm_devmem_lock);
-			goto error_radix;
-		}
-	}
-	mutex_unlock(&hmm_devmem_lock);
-
-	nid = dev_to_node(device);
-	if (nid < 0)
-		nid = numa_mem_id();
-
-	mem_hotplug_begin();
-	/*
-	 * For device private memory we call add_pages() as we only need to
-	 * allocate and initialize struct page for the device memory. More-
-	 * over the device memory is un-accessible thus we do not want to
-	 * create a linear mapping for the memory like arch_add_memory()
-	 * would do.
-	 *
-	 * For device public memory, which is accesible by the CPU, we do
-	 * want the linear mapping and thus use arch_add_memory().
-	 */
-	if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
-		ret = arch_add_memory(nid, align_start, align_size, NULL,
-				false);
-	else
-		ret = add_pages(nid, align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, NULL, false);
-	if (ret) {
-		mem_hotplug_done();
-		goto error_add_memory;
-	}
-	move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
-				align_start >> PAGE_SHIFT,
-				align_size >> PAGE_SHIFT, NULL);
-	mem_hotplug_done();
-
-	for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
-		struct page *page = pfn_to_page(pfn);
-
-		page->pgmap = &devmem->pagemap;
-	}
-	return 0;
-
-error_add_memory:
-	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
-error_radix:
-	hmm_devmem_radix_release(devmem->resource);
-error:
-	return ret;
-}
-
 /*
  * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
  *
@@ -1140,6 +993,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 {
 	struct hmm_devmem *devmem;
 	resource_size_t addr;
+	void *result;
 	int ret;
 
 	dev_pagemap_get_ops();
@@ -1194,14 +1048,18 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 	devmem->pfn_last = devmem->pfn_first +
 			   (resource_size(devmem->resource) >> PAGE_SHIFT);
 
-	ret = hmm_devmem_pages_create(devmem);
-	if (ret)
-		return ERR_PTR(ret);
-
-	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
-	if (ret)
-		return ERR_PTR(ret);
+	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	devmem->pagemap.res = *devmem->resource;
+	devmem->pagemap.page_fault = hmm_devmem_fault;
+	devmem->pagemap.page_free = hmm_devmem_free;
+	devmem->pagemap.altmap_valid = false;
+	devmem->pagemap.ref = &devmem->ref;
+	devmem->pagemap.data = devmem;
 
+	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
+			hmm_devmem_ref_kill);
+	if (IS_ERR(result))
+		return result;
 	return devmem;
 }
 EXPORT_SYMBOL(hmm_devmem_add);
@@ -1211,6 +1069,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 					   struct resource *res)
 {
 	struct hmm_devmem *devmem;
+	void *result;
 	int ret;
 
 	if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
@@ -1243,19 +1102,18 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 	devmem->pfn_last = devmem->pfn_first +
 			   (resource_size(devmem->resource) >> PAGE_SHIFT);
 
-	ret = hmm_devmem_pages_create(devmem);
-	if (ret)
-		return ERR_PTR(ret);
-
-	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
-	if (ret)
-		return ERR_PTR(ret);
-
-	ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
-			&devmem->ref);
-	if (ret)
-		return ERR_PTR(ret);
+	devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
+	devmem->pagemap.res = *devmem->resource;
+	devmem->pagemap.page_fault = hmm_devmem_fault;
+	devmem->pagemap.page_free = hmm_devmem_free;
+	devmem->pagemap.altmap_valid = false;
+	devmem->pagemap.ref = &devmem->ref;
+	devmem->pagemap.data = devmem;
 
+	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
+			hmm_devmem_ref_kill);
+	if (IS_ERR(result))
+		return result;
 	return devmem;
 }
 EXPORT_SYMBOL(hmm_devmem_add_resource);

[PATCH v5 7/7] mm, hmm: Mark hmm_devmem_{add, add_resource} EXPORT_SYMBOL_GPL

[Dan Williams]

The routines hmm_devmem_add(), and hmm_devmem_add_resource() duplicated
devm_memremap_pages() and are now simple now wrappers around the core
facility to inject a dev_pagemap instance into the global pgmap_radix
and hook page-idle events. The devm_memremap_pages() interface is base
infrastructure for HMM. HMM has more and deeper ties into the kernel
memory management implementation than base ZONE_DEVICE which is itself a
EXPORT_SYMBOL_GPL facility.

Originally, the HMM page structure creation routines copied the
devm_memremap_pages() code and reused ZONE_DEVICE. A cleanup to unify
the implementations was discussed during the initial review:
http://lkml.iu.edu/hypermail/linux/kernel/1701.2/00812.html
Recent work to extend devm_memremap_pages() for the peer-to-peer-DMA
facility enabled this cleanup to move forward.

In addition to the integration with devm_memremap_pages() HMM depends on
other GPL-only symbols:

    mmu_notifier_unregister_no_release
    percpu_ref
    region_intersects
    __class_create

It goes further to consume / indirectly expose functionality that is not
exported to any other driver:

    alloc_pages_vma
    walk_page_range

HMM is derived from devm_memremap_pages(), and extends deep core-kernel
fundamentals. Similar to devm_memremap_pages(), mark its entry points
EXPORT_SYMBOL_GPL().

Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 mm/hmm.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index c6cab5205b99..1d5a09087275 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1062,7 +1062,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
 		return result;
 	return devmem;
 }
-EXPORT_SYMBOL(hmm_devmem_add);
+EXPORT_SYMBOL_GPL(hmm_devmem_add);
 
 struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 					   struct device *device,
@@ -1116,7 +1116,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
 		return result;
 	return devmem;
 }
-EXPORT_SYMBOL(hmm_devmem_add_resource);
+EXPORT_SYMBOL_GPL(hmm_devmem_add_resource);
 
 /*
  * A device driver that wants to handle multiple devices memory through a

Re: [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Logan Gunthorpe]

On 12/09/18 08:22 PM, Dan Williams wrote:
> Given the fact that devm_memremap_pages() requires a percpu_ref that is
> torn down by devm_memremap_pages_release() the current support for
> mapping RAM is broken.
> 
> Support for remapping "System RAM" has been broken since the beginning
> and there is no existing user of this this code path, so just kill the
> support and make it an explicit error.
> 
> This cleanup also simplifies a follow-on patch to fix the error path
> when setting a devm release action for devm_memremap_pages_release()
> fails.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>

Logan

> ---
>  kernel/memremap.c |    9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index f95c7833db6d..92e838127767 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -202,15 +202,12 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  	is_ram = region_intersects(align_start, align_size,
>  		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
>  
> -	if (is_ram == REGION_MIXED) {
> -		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
> -				__func__, res);
> +	if (is_ram != REGION_DISJOINT) {
> +		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
> +				is_ram == REGION_MIXED ? "mixed" : "ram", res);
>  		return ERR_PTR(-ENXIO);
>  	}
>  
> -	if (is_ram == REGION_INTERSECTS)
> -		return __va(res->start);
> -
>  	if (!pgmap->ref)
>  		return ERR_PTR(-EINVAL);
>  
> 

Re: [PATCH v5 1/7] mm, devm_memremap_pages: Mark devm_memremap_pages() EXPORT_SYMBOL_GPL

[Logan Gunthorpe]

On 12/09/18 08:22 PM, Dan Williams wrote:
> devm_memremap_pages() is a facility that can create struct page entries
> for any arbitrary range and give drivers the ability to subvert core
> aspects of page management.
> 
> Specifically the facility is tightly integrated with the kernel's memory
> hotplug functionality. It injects an altmap argument deep into the
> architecture specific vmemmap implementation to allow allocating from
> specific reserved pages, and it has Linux specific assumptions about
> page structure reference counting relative to get_user_pages() and
> get_user_pages_fast(). It was an oversight and a mistake that this was
> not marked EXPORT_SYMBOL_GPL from the outset.
> 
> Again, devm_memremap_pagex() exposes and relies upon core kernel
> internal assumptions and will continue to evolve along with 'struct
> page', memory hotplug, and support for new memory types / topologies.
> Only an in-kernel GPL-only driver is expected to keep up with this
> ongoing evolution. This interface, and functionality derived from this
> interface, is not suitable for kernel-external drivers.
> 
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Logan Gunthorpe <logang@deltatee.com>

Mostly to say that I agree with you and Christoph on this debate and
that the change to GPL does not affect my P2PDMA work.

Logan

Re: [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Christoph Hellwig]

On Wed, Sep 12, 2018 at 07:22:11PM -0700, Dan Williams wrote:
> Given the fact that devm_memremap_pages() requires a percpu_ref that is
> torn down by devm_memremap_pages_release() the current support for
> mapping RAM is broken.

I agree.  Do you remember why we even added it in the first place?

Signed-off-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 3/7] mm, devm_memremap_pages: Fix shutdown handling

[Christoph Hellwig]

> An argument could be made to require that the ->kill() operation be set
> in the @pgmap arg rather than passed in separately. However, it helps
> code readability, tracking the lifetime of a given instance, to be able
> to grep the kill routine directly at the devm_memremap_pages() call
> site.

I generally do not like passing redundant argument, and I don't really
see why this case is different.  Or in other ways I'd like to make
your above argument..

Except for that the patch looks good to me.

Re: [PATCH v5 4/7] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support

[Christoph Hellwig]

On Wed, Sep 12, 2018 at 07:22:22PM -0700, Dan Williams wrote:
> In preparation for consolidating all ZONE_DEVICE enabling via
> devm_memremap_pages(), teach it how to handle the constraints of
> MEMORY_DEVICE_PRIVATE ranges.

MEMORY_DEVICE_PRIVATE still somehow boggles my mind, but otherwise
this looks sensible to me:

Acked-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v5 5/7] mm, hmm: Use devm semantics for hmm_devmem_{add, remove}

[Christoph Hellwig]

On Wed, Sep 12, 2018 at 07:22:27PM -0700, Dan Williams wrote:
> devm semantics arrange for resources to be torn down when
> device-driver-probe fails or when device-driver-release completes.
> Similar to devm_memremap_pages() there is no need to support an explicit
> remove operation when the users properly adhere to devm semantics.
> 
> Note that devm_kzalloc() automatically handles allocating node-local
> memory.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Given that we have no single user of these function I still think we
should just remove them.

Re: [PATCH v5 5/7] mm, hmm: Use devm semantics for hmm_devmem_{add, remove}

[Jerome Glisse]

On Fri, Sep 14, 2018 at 03:18:38PM +0200, Christoph Hellwig wrote:
> On Wed, Sep 12, 2018 at 07:22:27PM -0700, Dan Williams wrote:
> > devm semantics arrange for resources to be torn down when
> > device-driver-probe fails or when device-driver-release completes.
> > Similar to devm_memremap_pages() there is no need to support an explicit
> > remove operation when the users properly adhere to devm semantics.
> > 
> > Note that devm_kzalloc() automatically handles allocating node-local
> > memory.
> > 
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Given that we have no single user of these function I still think we
> should just remove them.

It is in the process of being upstreamed:

https://cgit.freedesktop.org/~glisse/linux/log/?h=nouveau-hmm-v01

and more users are coming for other devices.

Yes it is taking time ... things never goes as planed.

Cheers,
Jérôme

Re: [PATCH v5 3/7] mm, devm_memremap_pages: Fix shutdown handling

[Dan Williams]

On Fri, Sep 14, 2018 at 6:16 AM, Christoph Hellwig <hch@lst.de> wrote:
>> An argument could be made to require that the ->kill() operation be set
>> in the @pgmap arg rather than passed in separately. However, it helps
>> code readability, tracking the lifetime of a given instance, to be able
>> to grep the kill routine directly at the devm_memremap_pages() call
>> site.
>
> I generally do not like passing redundant argument, and I don't really
> see why this case is different.  Or in other ways I'd like to make
> your above argument..

Logan had similar feedback, and now the chorus is getting louder. I
personally like how I can do this with grep:

drivers/dax/pmem.c:114: addr = devm_memremap_pages(dev,
&dax_pmem->pgmap, dax_pmem_percpu_kill);
--
drivers/nvdimm/pmem.c:411:              addr =
devm_memremap_pages(dev, &pmem->pgmap,
drivers/nvdimm/pmem.c-412-                              pmem_freeze_queue);
--
drivers/nvdimm/pmem.c:425:              addr =
devm_memremap_pages(dev, &pmem->pgmap,
drivers/nvdimm/pmem.c-426-                              pmem_freeze_queue);
--
mm/hmm.c:1059:  result = devm_memremap_pages(devmem->device, &devmem->pagemap,
mm/hmm.c-1060-                  hmm_devmem_ref_kill);
--
mm/hmm.c:1113:  result = devm_memremap_pages(devmem->device, &devmem->pagemap,
mm/hmm.c-1114-                  hmm_devmem_ref_kill);

...and see all of the kill() variants, but the redundancy will likely
continue to bother folks.

> Except for that the patch looks good to me.

Thanks, I'll fix it up to drop the redundant arg.

Re: [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Dan Williams]

On Fri, Sep 14, 2018 at 6:14 AM, Christoph Hellwig <hch@lst.de> wrote:
> On Wed, Sep 12, 2018 at 07:22:11PM -0700, Dan Williams wrote:
>> Given the fact that devm_memremap_pages() requires a percpu_ref that is
>> torn down by devm_memremap_pages_release() the current support for
>> mapping RAM is broken.
>
> I agree.  Do you remember why we even added it in the first place?

It was initially a copy over from memremap() that catches these
attempts and returns a direct-map pointer.

Re: [PATCH v5 2/7] mm, devm_memremap_pages: Kill mapping "System RAM" support

[Jerome Glisse]

On Wed, Sep 12, 2018 at 07:22:11PM -0700, Dan Williams wrote:
> Given the fact that devm_memremap_pages() requires a percpu_ref that is
> torn down by devm_memremap_pages_release() the current support for
> mapping RAM is broken.
> 
> Support for remapping "System RAM" has been broken since the beginning
> and there is no existing user of this this code path, so just kill the
> support and make it an explicit error.
> 
> This cleanup also simplifies a follow-on patch to fix the error path
> when setting a devm release action for devm_memremap_pages_release()
> fails.
> 
> Cc: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  kernel/memremap.c |    9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index f95c7833db6d..92e838127767 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -202,15 +202,12 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  	is_ram = region_intersects(align_start, align_size,
>  		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
>  
> -	if (is_ram == REGION_MIXED) {
> -		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
> -				__func__, res);
> +	if (is_ram != REGION_DISJOINT) {
> +		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
> +				is_ram == REGION_MIXED ? "mixed" : "ram", res);
>  		return ERR_PTR(-ENXIO);
>  	}
>  
> -	if (is_ram == REGION_INTERSECTS)
> -		return __va(res->start);
> -
>  	if (!pgmap->ref)
>  		return ERR_PTR(-EINVAL);
>  
> 

Re: [PATCH v5 3/7] mm, devm_memremap_pages: Fix shutdown handling

[Jerome Glisse]

On Wed, Sep 12, 2018 at 07:22:17PM -0700, Dan Williams wrote:
> The last step before devm_memremap_pages() returns success is to
> allocate a release action, devm_memremap_pages_release(), to tear the
> entire setup down. However, the result from devm_add_action() is not
> checked.
> 
> Checking the error from devm_add_action() is not enough. The api
> currently relies on the fact that the percpu_ref it is using is killed
> by the time the devm_memremap_pages_release() is run. Rather than
> continue this awkward situation, offload the responsibility of killing
> the percpu_ref to devm_memremap_pages_release() directly. This allows
> devm_memremap_pages() to do the right thing  relative to init failures
> and shutdown.
> 
> Without this change we could fail to register the teardown of
> devm_memremap_pages(). The likelihood of hitting this failure is tiny as
> small memory allocations almost always succeed. However, the impact of
> the failure is large given any future reconfiguration, or
> disable/enable, of an nvdimm namespace will fail forever as subsequent
> calls to devm_memremap_pages() will fail to setup the pgmap_radix since
> there will be stale entries for the physical address range.
> 
> An argument could be made to require that the ->kill() operation be set
> in the @pgmap arg rather than passed in separately. However, it helps
> code readability, tracking the lifetime of a given instance, to be able
> to grep the kill routine directly at the devm_memremap_pages() call
> site.
> 
> Cc: <stable@vger.kernel.org>
> Fixes: e8d513483300 ("memremap: change devm_memremap_pages interface...")
> Cc: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> Reported-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/dax/pmem.c                |   15 +++------------
>  drivers/nvdimm/pmem.c             |   18 ++++++++----------
>  include/linux/memremap.h          |    7 +++++--
>  kernel/memremap.c                 |   36 +++++++++++++++++++-----------------
>  tools/testing/nvdimm/test/iomap.c |   21 ++++++++++++++++++---
>  5 files changed, 53 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
> index 99e2aace8078..c1e03d769e6d 100644
> --- a/drivers/dax/pmem.c
> +++ b/drivers/dax/pmem.c
> @@ -48,9 +48,8 @@ static void dax_pmem_percpu_exit(void *data)
>  	percpu_ref_exit(ref);
>  }
>  
> -static void dax_pmem_percpu_kill(void *data)
> +static void dax_pmem_percpu_kill(struct percpu_ref *ref)
>  {
> -	struct percpu_ref *ref = data;
>  	struct dax_pmem *dax_pmem = to_dax_pmem(ref);
>  
>  	dev_dbg(dax_pmem->dev, "trace\n");
> @@ -112,17 +111,9 @@ static int dax_pmem_probe(struct device *dev)
>  	}
>  
>  	dax_pmem->pgmap.ref = &dax_pmem->ref;
> -	addr = devm_memremap_pages(dev, &dax_pmem->pgmap);
> -	if (IS_ERR(addr)) {
> -		devm_remove_action(dev, dax_pmem_percpu_exit, &dax_pmem->ref);
> -		percpu_ref_exit(&dax_pmem->ref);
> +	addr = devm_memremap_pages(dev, &dax_pmem->pgmap, dax_pmem_percpu_kill);
> +	if (IS_ERR(addr))
>  		return PTR_ERR(addr);
> -	}
> -
> -	rc = devm_add_action_or_reset(dev, dax_pmem_percpu_kill,
> -							&dax_pmem->ref);
> -	if (rc)
> -		return rc;
>  
>  	/* adjust the dax_region resource to the start of data */
>  	memcpy(&res, &dax_pmem->pgmap.res, sizeof(res));
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 6071e2942053..c9cad5ebea5b 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -309,8 +309,11 @@ static void pmem_release_queue(void *q)
>  	blk_cleanup_queue(q);
>  }
>  
> -static void pmem_freeze_queue(void *q)
> +static void pmem_freeze_queue(struct percpu_ref *ref)
>  {
> +	struct request_queue *q;
> +
> +	q = container_of(ref, typeof(*q), q_usage_counter);
>  	blk_freeze_queue_start(q);
>  }
>  
> @@ -405,7 +408,8 @@ static int pmem_attach_disk(struct device *dev,
>  	if (is_nd_pfn(dev)) {
>  		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
>  			return -ENOMEM;
> -		addr = devm_memremap_pages(dev, &pmem->pgmap);
> +		addr = devm_memremap_pages(dev, &pmem->pgmap,
> +				pmem_freeze_queue);
>  		pfn_sb = nd_pfn->pfn_sb;
>  		pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
>  		pmem->pfn_pad = resource_size(res) -
> @@ -418,20 +422,14 @@ static int pmem_attach_disk(struct device *dev,
>  		pmem->pgmap.altmap_valid = false;
>  		if (setup_pagemap_fsdax(dev, &pmem->pgmap))
>  			return -ENOMEM;
> -		addr = devm_memremap_pages(dev, &pmem->pgmap);
> +		addr = devm_memremap_pages(dev, &pmem->pgmap,
> +				pmem_freeze_queue);
>  		pmem->pfn_flags |= PFN_MAP;
>  		memcpy(&bb_res, &pmem->pgmap.res, sizeof(bb_res));
>  	} else
>  		addr = devm_memremap(dev, pmem->phys_addr,
>  				pmem->size, ARCH_MEMREMAP_PMEM);
>  
> -	/*
> -	 * At release time the queue must be frozen before
> -	 * devm_memremap_pages is unwound
> -	 */
> -	if (devm_add_action_or_reset(dev, pmem_freeze_queue, q))
> -		return -ENOMEM;
> -
>  	if (IS_ERR(addr))
>  		return PTR_ERR(addr);
>  	pmem->virt_addr = addr;
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index f91f9e763557..71f5e7c7dfb9 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -106,6 +106,7 @@ typedef void (*dev_page_free_t)(struct page *page, void *data);
>   * @altmap: pre-allocated/reserved memory for vmemmap allocations
>   * @res: physical address range covered by @ref
>   * @ref: reference count that pins the devm_memremap_pages() mapping
> + * @kill: callback to transition @ref to the dead state
>   * @dev: host device of the mapping for debug
>   * @data: private data pointer for page_free()
>   * @type: memory type: see MEMORY_* in memory_hotplug.h
> @@ -117,13 +118,15 @@ struct dev_pagemap {
>  	bool altmap_valid;
>  	struct resource res;
>  	struct percpu_ref *ref;
> +	void (*kill)(struct percpu_ref *ref);
>  	struct device *dev;
>  	void *data;
>  	enum memory_type type;
>  };
>  
>  #ifdef CONFIG_ZONE_DEVICE
> -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
> +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
> +		void (*kill)(struct percpu_ref *));
>  struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
>  		struct dev_pagemap *pgmap);
>  
> @@ -131,7 +134,7 @@ unsigned long vmem_altmap_offset(struct vmem_altmap *altmap);
>  void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns);
>  #else
>  static inline void *devm_memremap_pages(struct device *dev,
> -		struct dev_pagemap *pgmap)
> +		struct dev_pagemap *pgmap, void (*kill)(struct percpu_ref *))
>  {
>  	/*
>  	 * Fail attempts to call devm_memremap_pages() without
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 92e838127767..ab5eb570d28d 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -122,14 +122,10 @@ static void devm_memremap_pages_release(void *data)
>  	resource_size_t align_start, align_size;
>  	unsigned long pfn;
>  
> +	pgmap->kill(pgmap->ref);
>  	for_each_device_pfn(pfn, pgmap)
>  		put_page(pfn_to_page(pfn));
>  
> -	if (percpu_ref_tryget_live(pgmap->ref)) {
> -		dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
> -		percpu_ref_put(pgmap->ref);
> -	}
> -
>  	/* pages are dead and unused, undo the arch mapping */
>  	align_start = res->start & ~(SECTION_SIZE - 1);
>  	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
> @@ -150,7 +146,8 @@ static void devm_memremap_pages_release(void *data)
>  /**
>   * devm_memremap_pages - remap and provide memmap backing for the given resource
>   * @dev: hosting device for @res
> - * @pgmap: pointer to a struct dev_pgmap
> + * @pgmap: pointer to a struct dev_pagemap
> + * @kill: routine to kill @pgmap->ref
>   *
>   * Notes:
>   * 1/ At a minimum the res, ref and type members of @pgmap must be initialized
> @@ -159,17 +156,15 @@ static void devm_memremap_pages_release(void *data)
>   * 2/ The altmap field may optionally be initialized, in which case altmap_valid
>   *    must be set to true
>   *
> - * 3/ pgmap.ref must be 'live' on entry and 'dead' before devm_memunmap_pages()
> - *    time (or devm release event). The expected order of events is that ref has
> - *    been through percpu_ref_kill() before devm_memremap_pages_release(). The
> - *    wait for the completion of all references being dropped and
> - *    percpu_ref_exit() must occur after devm_memremap_pages_release().
> + * 3/ pgmap->ref must be 'live' on entry and will be killed at
> + *    devm_memremap_pages_release() time, or if this routine fails.
>   *
>   * 4/ res is expected to be a host memory range that could feasibly be
>   *    treated as a "System RAM" range, i.e. not a device mmio range, but
>   *    this is not enforced.
>   */
> -void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> +void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
> +		void (*kill)(struct percpu_ref *))
>  {
>  	resource_size_t align_start, align_size, align_end;
>  	struct vmem_altmap *altmap = pgmap->altmap_valid ?
> @@ -180,6 +175,9 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  	int error, nid, is_ram;
>  	struct dev_pagemap *conflict_pgmap;
>  
> +	if (!pgmap->ref || !kill)
> +		return ERR_PTR(-EINVAL);
> +
>  	align_start = res->start & ~(SECTION_SIZE - 1);
>  	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
>  		- align_start;
> @@ -205,12 +203,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  	if (is_ram != REGION_DISJOINT) {
>  		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
>  				is_ram == REGION_MIXED ? "mixed" : "ram", res);
> -		return ERR_PTR(-ENXIO);
> +		error = -ENXIO;
> +		goto err_init;
>  	}
>  
> -	if (!pgmap->ref)
> -		return ERR_PTR(-EINVAL);
> -
>  	pgmap->dev = dev;
>  
>  	mutex_lock(&pgmap_lock);
> @@ -267,7 +263,11 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>  		percpu_ref_get(pgmap->ref);
>  	}
>  
> -	devm_add_action(dev, devm_memremap_pages_release, pgmap);
> +	pgmap->kill = kill;
> +	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
> +			pgmap);
> +	if (error)
> +		return ERR_PTR(error);
>  
>  	return __va(res->start);
>  
> @@ -278,6 +278,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
>   err_pfn_remap:
>   err_radix:
>  	pgmap_radix_release(res, pgoff);
> + err_init:
> +	kill(pgmap->ref);
>  	return ERR_PTR(error);
>  }
>  EXPORT_SYMBOL_GPL(devm_memremap_pages);
> diff --git a/tools/testing/nvdimm/test/iomap.c b/tools/testing/nvdimm/test/iomap.c
> index ff9d3a5825e1..ad544e6476a9 100644
> --- a/tools/testing/nvdimm/test/iomap.c
> +++ b/tools/testing/nvdimm/test/iomap.c
> @@ -104,14 +104,29 @@ void *__wrap_devm_memremap(struct device *dev, resource_size_t offset,
>  }
>  EXPORT_SYMBOL(__wrap_devm_memremap);
>  
> -void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> +static void nfit_test_kill(void *_pgmap)
> +{
> +	struct dev_pagemap *pgmap = _pgmap;
> +
> +	pgmap->kill(pgmap->ref);
> +}
> +
> +void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
> +		void (*kill)(struct percpu_ref *))
>  {
>  	resource_size_t offset = pgmap->res.start;
>  	struct nfit_test_resource *nfit_res = get_nfit_res(offset);
>  
> -	if (nfit_res)
> +	if (nfit_res) {
> +		int rc;
> +
> +		pgmap->kill = kill;
> +		rc = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
> +		if (rc)
> +			return ERR_PTR(rc);
>  		return nfit_res->buf + offset - nfit_res->res.start;
> -	return devm_memremap_pages(dev, pgmap);
> +	}
> +	return devm_memremap_pages(dev, pgmap, kill);
>  }
>  EXPORT_SYMBOL(__wrap_devm_memremap_pages);
>  
> 

Re: [PATCH v5 4/7] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support

[Jerome Glisse]

Below is v2 of this patch with v2 it works properly:


From: Dan Williams <dan.j.williams@intel.com>
Date: Wed, 12 Sep 2018 19:22:22 -0700
Subject: [PATCH] mm, devm_memremap_pages: Add MEMORY_DEVICE_PRIVATE support v2
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In preparation for consolidating all ZONE_DEVICE enabling via
devm_memremap_pages(), teach it how to handle the constraints of
MEMORY_DEVICE_PRIVATE ranges.

Changed since v1:
    - move_pfn_range_to_zone() for private device memory too

Cc: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 kernel/memremap.c | 53 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 41 insertions(+), 12 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 5b3b6f23fd35..adba623a25f4 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -132,9 +132,15 @@ static void devm_memremap_pages_release(void *data)
 		- align_start;
 
 	mem_hotplug_begin();
-	arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
-			&pgmap->altmap : NULL);
-	kasan_remove_zero_shadow(__va(align_start), align_size);
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		pfn = align_start >> PAGE_SHIFT;
+		__remove_pages(page_zone(pfn_to_page(pfn)), pfn,
+				align_size >> PAGE_SHIFT, NULL);
+	} else {
+		arch_remove_memory(align_start, align_size,
+				pgmap->altmap_valid ? &pgmap->altmap : NULL);
+		kasan_remove_zero_shadow(__va(align_start), align_size);
+	}
 	mem_hotplug_done();
 
 	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
@@ -234,17 +240,40 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap,
 		goto err_pfn_remap;
 
 	mem_hotplug_begin();
-	error = kasan_add_zero_shadow(__va(align_start), align_size);
-	if (error) {
-		mem_hotplug_done();
-		goto err_kasan;
+
+	/*
+	 * For device private memory we call add_pages() as we only need to
+	 * allocate and initialize struct page for the device memory. More-
+	 * over the device memory is un-accessible thus we do not want to
+	 * create a linear mapping for the memory like arch_add_memory()
+	 * would do.
+	 *
+	 * For all other device memory types, which are accessible by
+	 * the CPU, we do want the linear mapping and thus use
+	 * arch_add_memory().
+	 */
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+		error = add_pages(nid, align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT, NULL, false);
+	} else {
+		error = kasan_add_zero_shadow(__va(align_start), align_size);
+		if (error) {
+			mem_hotplug_done();
+			goto err_kasan;
+		}
+
+		error = arch_add_memory(nid, align_start, align_size, altmap,
+				false);
+	}
+
+	if (!error) {
+		struct zone *zone;
+
+		zone = &NODE_DATA(nid)->node_zones[ZONE_DEVICE];
+		move_pfn_range_to_zone(zone, align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT, altmap);
 	}
 
-	error = arch_add_memory(nid, align_start, align_size, altmap, false);
-	if (!error)
-		move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
-					align_start >> PAGE_SHIFT,
-					align_size >> PAGE_SHIFT, altmap);
 	mem_hotplug_done();
 	if (error)
 		goto err_add_memory;
-- 
2.17.1

Re: [PATCH v5 5/7] mm, hmm: Use devm semantics for hmm_devmem_{add, remove}

[Jerome Glisse]

On Wed, Sep 12, 2018 at 07:22:27PM -0700, Dan Williams wrote:
> devm semantics arrange for resources to be torn down when
> device-driver-probe fails or when device-driver-release completes.
> Similar to devm_memremap_pages() there is no need to support an explicit
> remove operation when the users properly adhere to devm semantics.
> 
> Note that devm_kzalloc() automatically handles allocating node-local
> memory.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  include/linux/hmm.h |    4 --
>  mm/hmm.c            |  127 ++++++++++-----------------------------------------
>  2 files changed, 25 insertions(+), 106 deletions(-)
> 
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 4c92e3ba3e16..5ec8635f602c 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -499,8 +499,7 @@ struct hmm_devmem {
>   * enough and allocate struct page for it.
>   *
>   * The device driver can wrap the hmm_devmem struct inside a private device
> - * driver struct. The device driver must call hmm_devmem_remove() before the
> - * device goes away and before freeing the hmm_devmem struct memory.
> + * driver struct.
>   */
>  struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  				  struct device *device,
> @@ -508,7 +507,6 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  					   struct device *device,
>  					   struct resource *res);
> -void hmm_devmem_remove(struct hmm_devmem *devmem);
>  
>  /*
>   * hmm_devmem_page_set_drvdata - set per-page driver data field
> diff --git a/mm/hmm.c b/mm/hmm.c
> index c968e49f7a0c..ec1d9eccf176 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -939,7 +939,6 @@ static void hmm_devmem_ref_exit(void *data)
>  
>  	devmem = container_of(ref, struct hmm_devmem, ref);
>  	percpu_ref_exit(ref);
> -	devm_remove_action(devmem->device, &hmm_devmem_ref_exit, data);
>  }
>  
>  static void hmm_devmem_ref_kill(void *data)
> @@ -950,7 +949,6 @@ static void hmm_devmem_ref_kill(void *data)
>  	devmem = container_of(ref, struct hmm_devmem, ref);
>  	percpu_ref_kill(ref);
>  	wait_for_completion(&devmem->completion);
> -	devm_remove_action(devmem->device, &hmm_devmem_ref_kill, data);
>  }
>  
>  static int hmm_devmem_fault(struct vm_area_struct *vma,
> @@ -988,7 +986,7 @@ static void hmm_devmem_radix_release(struct resource *resource)
>  	mutex_unlock(&hmm_devmem_lock);
>  }
>  
> -static void hmm_devmem_release(struct device *dev, void *data)
> +static void hmm_devmem_release(void *data)
>  {
>  	struct hmm_devmem *devmem = data;
>  	struct resource *resource = devmem->resource;
> @@ -996,11 +994,6 @@ static void hmm_devmem_release(struct device *dev, void *data)
>  	struct zone *zone;
>  	struct page *page;
>  
> -	if (percpu_ref_tryget_live(&devmem->ref)) {
> -		dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
> -		percpu_ref_put(&devmem->ref);
> -	}
> -
>  	/* pages are dead and unused, undo the arch mapping */
>  	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
>  	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
> @@ -1124,19 +1117,6 @@ static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
>  	return ret;
>  }
>  
> -static int hmm_devmem_match(struct device *dev, void *data, void *match_data)
> -{
> -	struct hmm_devmem *devmem = data;
> -
> -	return devmem->resource == match_data;
> -}
> -
> -static void hmm_devmem_pages_remove(struct hmm_devmem *devmem)
> -{
> -	devres_release(devmem->device, &hmm_devmem_release,
> -		       &hmm_devmem_match, devmem->resource);
> -}
> -
>  /*
>   * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
>   *
> @@ -1164,8 +1144,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  
>  	dev_pagemap_get_ops();
>  
> -	devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
> -				   GFP_KERNEL, dev_to_node(device));
> +	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
>  	if (!devmem)
>  		return ERR_PTR(-ENOMEM);
>  
> @@ -1179,11 +1158,11 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
>  			      0, GFP_KERNEL);
>  	if (ret)
> -		goto error_percpu_ref;
> +		return ERR_PTR(ret);
>  
> -	ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
> +	ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit, &devmem->ref);
>  	if (ret)
> -		goto error_devm_add_action;
> +		return ERR_PTR(ret);
>  
>  	size = ALIGN(size, PA_SECTION_SIZE);
>  	addr = min((unsigned long)iomem_resource.end,
> @@ -1203,16 +1182,12 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  
>  		devmem->resource = devm_request_mem_region(device, addr, size,
>  							   dev_name(device));
> -		if (!devmem->resource) {
> -			ret = -ENOMEM;
> -			goto error_no_resource;
> -		}
> +		if (!devmem->resource)
> +			return ERR_PTR(-ENOMEM);
>  		break;
>  	}
> -	if (!devmem->resource) {
> -		ret = -ERANGE;
> -		goto error_no_resource;
> -	}
> +	if (!devmem->resource)
> +		return ERR_PTR(-ERANGE);
>  
>  	devmem->resource->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
>  	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
> @@ -1221,28 +1196,13 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  
>  	ret = hmm_devmem_pages_create(devmem);
>  	if (ret)
> -		goto error_pages;
> -
> -	devres_add(device, devmem);
> +		return ERR_PTR(ret);
>  
> -	ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
> -	if (ret) {
> -		hmm_devmem_remove(devmem);
> +	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> +	if (ret)
>  		return ERR_PTR(ret);
> -	}
>  
>  	return devmem;
> -
> -error_pages:
> -	devm_release_mem_region(device, devmem->resource->start,
> -				resource_size(devmem->resource));
> -error_no_resource:
> -error_devm_add_action:
> -	hmm_devmem_ref_kill(&devmem->ref);
> -	hmm_devmem_ref_exit(&devmem->ref);
> -error_percpu_ref:
> -	devres_free(devmem);
> -	return ERR_PTR(ret);
>  }
>  EXPORT_SYMBOL(hmm_devmem_add);
>  
> @@ -1258,8 +1218,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  
>  	dev_pagemap_get_ops();
>  
> -	devmem = devres_alloc_node(&hmm_devmem_release, sizeof(*devmem),
> -				   GFP_KERNEL, dev_to_node(device));
> +	devmem = devm_kzalloc(device, sizeof(*devmem), GFP_KERNEL);
>  	if (!devmem)
>  		return ERR_PTR(-ENOMEM);
>  
> @@ -1273,12 +1232,12 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  	ret = percpu_ref_init(&devmem->ref, &hmm_devmem_ref_release,
>  			      0, GFP_KERNEL);
>  	if (ret)
> -		goto error_percpu_ref;
> +		return ERR_PTR(ret);
>  
> -	ret = devm_add_action(device, hmm_devmem_ref_exit, &devmem->ref);
> +	ret = devm_add_action_or_reset(device, hmm_devmem_ref_exit,
> +			&devmem->ref);
>  	if (ret)
> -		goto error_devm_add_action;
> -
> +		return ERR_PTR(ret);
>  
>  	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;
>  	devmem->pfn_last = devmem->pfn_first +
> @@ -1286,59 +1245,21 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  
>  	ret = hmm_devmem_pages_create(devmem);
>  	if (ret)
> -		goto error_devm_add_action;
> +		return ERR_PTR(ret);
>  
> -	devres_add(device, devmem);
> +	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> +	if (ret)
> +		return ERR_PTR(ret);
>  
> -	ret = devm_add_action(device, hmm_devmem_ref_kill, &devmem->ref);
> -	if (ret) {
> -		hmm_devmem_remove(devmem);
> +	ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
> +			&devmem->ref);
> +	if (ret)
>  		return ERR_PTR(ret);
> -	}
>  
>  	return devmem;
> -
> -error_devm_add_action:
> -	hmm_devmem_ref_kill(&devmem->ref);
> -	hmm_devmem_ref_exit(&devmem->ref);
> -error_percpu_ref:
> -	devres_free(devmem);
> -	return ERR_PTR(ret);
>  }
>  EXPORT_SYMBOL(hmm_devmem_add_resource);
>  
> -/*
> - * hmm_devmem_remove() - remove device memory (kill and free ZONE_DEVICE)
> - *
> - * @devmem: hmm_devmem struct use to track and manage the ZONE_DEVICE memory
> - *
> - * This will hot-unplug memory that was hotplugged by hmm_devmem_add on behalf
> - * of the device driver. It will free struct page and remove the resource that
> - * reserved the physical address range for this device memory.
> - */
> -void hmm_devmem_remove(struct hmm_devmem *devmem)
> -{
> -	resource_size_t start, size;
> -	struct device *device;
> -	bool cdm = false;
> -
> -	if (!devmem)
> -		return;
> -
> -	device = devmem->device;
> -	start = devmem->resource->start;
> -	size = resource_size(devmem->resource);
> -
> -	cdm = devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY;
> -	hmm_devmem_ref_kill(&devmem->ref);
> -	hmm_devmem_ref_exit(&devmem->ref);
> -	hmm_devmem_pages_remove(devmem);
> -
> -	if (!cdm)
> -		devm_release_mem_region(device, start, size);
> -}
> -EXPORT_SYMBOL(hmm_devmem_remove);
> -
>  /*
>   * A device driver that wants to handle multiple devices memory through a
>   * single fake device can use hmm_device to do so. This is purely a helper
> 

Re: [PATCH v5 6/7] mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()

[Jerome Glisse]

On Wed, Sep 12, 2018 at 07:22:33PM -0700, Dan Williams wrote:
> Commit e8d513483300 "memremap: change devm_memremap_pages interface to
> use struct dev_pagemap" refactored devm_memremap_pages() to allow a
> dev_pagemap instance to be supplied. Passing in a dev_pagemap interface
> simplifies the design of pgmap type drivers in that they can rely on
> container_of() to lookup any private data associated with the given
> dev_pagemap instance.
> 
> In addition to the cleanups this also gives hmm users multi-order-radix
> improvements that arrived with commit ab1b597ee0e4 "mm,
> devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups"
> 
> As part of the conversion to the devm_memremap_pages() method of
> handling the percpu_ref relative to when pages are put, the percpu_ref
> completion needs to move to hmm_devmem_ref_exit(). See commit
> 71389703839e ("mm, zone_device: Replace {get, put}_zone_device_page...")
> for details.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  mm/hmm.c |  194 ++++++++------------------------------------------------------
>  1 file changed, 26 insertions(+), 168 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index ec1d9eccf176..c6cab5205b99 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -938,17 +938,16 @@ static void hmm_devmem_ref_exit(void *data)
>  	struct hmm_devmem *devmem;
>  
>  	devmem = container_of(ref, struct hmm_devmem, ref);
> +	wait_for_completion(&devmem->completion);
>  	percpu_ref_exit(ref);
>  }
>  
> -static void hmm_devmem_ref_kill(void *data)
> +static void hmm_devmem_ref_kill(struct percpu_ref *ref)
>  {
> -	struct percpu_ref *ref = data;
>  	struct hmm_devmem *devmem;
>  
>  	devmem = container_of(ref, struct hmm_devmem, ref);
>  	percpu_ref_kill(ref);
> -	wait_for_completion(&devmem->completion);
>  }
>  
>  static int hmm_devmem_fault(struct vm_area_struct *vma,
> @@ -971,152 +970,6 @@ static void hmm_devmem_free(struct page *page, void *data)
>  	devmem->ops->free(devmem, page);
>  }
>  
> -static DEFINE_MUTEX(hmm_devmem_lock);
> -static RADIX_TREE(hmm_devmem_radix, GFP_KERNEL);
> -
> -static void hmm_devmem_radix_release(struct resource *resource)
> -{
> -	resource_size_t key;
> -
> -	mutex_lock(&hmm_devmem_lock);
> -	for (key = resource->start;
> -	     key <= resource->end;
> -	     key += PA_SECTION_SIZE)
> -		radix_tree_delete(&hmm_devmem_radix, key >> PA_SECTION_SHIFT);
> -	mutex_unlock(&hmm_devmem_lock);
> -}
> -
> -static void hmm_devmem_release(void *data)
> -{
> -	struct hmm_devmem *devmem = data;
> -	struct resource *resource = devmem->resource;
> -	unsigned long start_pfn, npages;
> -	struct zone *zone;
> -	struct page *page;
> -
> -	/* pages are dead and unused, undo the arch mapping */
> -	start_pfn = (resource->start & ~(PA_SECTION_SIZE - 1)) >> PAGE_SHIFT;
> -	npages = ALIGN(resource_size(resource), PA_SECTION_SIZE) >> PAGE_SHIFT;
> -
> -	page = pfn_to_page(start_pfn);
> -	zone = page_zone(page);
> -
> -	mem_hotplug_begin();
> -	if (resource->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY)
> -		__remove_pages(zone, start_pfn, npages, NULL);
> -	else
> -		arch_remove_memory(start_pfn << PAGE_SHIFT,
> -				   npages << PAGE_SHIFT, NULL);
> -	mem_hotplug_done();
> -
> -	hmm_devmem_radix_release(resource);
> -}
> -
> -static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
> -{
> -	resource_size_t key, align_start, align_size, align_end;
> -	struct device *device = devmem->device;
> -	int ret, nid, is_ram;
> -	unsigned long pfn;
> -
> -	align_start = devmem->resource->start & ~(PA_SECTION_SIZE - 1);
> -	align_size = ALIGN(devmem->resource->start +
> -			   resource_size(devmem->resource),
> -			   PA_SECTION_SIZE) - align_start;
> -
> -	is_ram = region_intersects(align_start, align_size,
> -				   IORESOURCE_SYSTEM_RAM,
> -				   IORES_DESC_NONE);
> -	if (is_ram == REGION_MIXED) {
> -		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
> -				__func__, devmem->resource);
> -		return -ENXIO;
> -	}
> -	if (is_ram == REGION_INTERSECTS)
> -		return -ENXIO;
> -
> -	if (devmem->resource->desc == IORES_DESC_DEVICE_PUBLIC_MEMORY)
> -		devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
> -	else
> -		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> -
> -	devmem->pagemap.res = *devmem->resource;
> -	devmem->pagemap.page_fault = hmm_devmem_fault;
> -	devmem->pagemap.page_free = hmm_devmem_free;
> -	devmem->pagemap.dev = devmem->device;
> -	devmem->pagemap.ref = &devmem->ref;
> -	devmem->pagemap.data = devmem;
> -
> -	mutex_lock(&hmm_devmem_lock);
> -	align_end = align_start + align_size - 1;
> -	for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) {
> -		struct hmm_devmem *dup;
> -
> -		dup = radix_tree_lookup(&hmm_devmem_radix,
> -					key >> PA_SECTION_SHIFT);
> -		if (dup) {
> -			dev_err(device, "%s: collides with mapping for %s\n",
> -				__func__, dev_name(dup->device));
> -			mutex_unlock(&hmm_devmem_lock);
> -			ret = -EBUSY;
> -			goto error;
> -		}
> -		ret = radix_tree_insert(&hmm_devmem_radix,
> -					key >> PA_SECTION_SHIFT,
> -					devmem);
> -		if (ret) {
> -			dev_err(device, "%s: failed: %d\n", __func__, ret);
> -			mutex_unlock(&hmm_devmem_lock);
> -			goto error_radix;
> -		}
> -	}
> -	mutex_unlock(&hmm_devmem_lock);
> -
> -	nid = dev_to_node(device);
> -	if (nid < 0)
> -		nid = numa_mem_id();
> -
> -	mem_hotplug_begin();
> -	/*
> -	 * For device private memory we call add_pages() as we only need to
> -	 * allocate and initialize struct page for the device memory. More-
> -	 * over the device memory is un-accessible thus we do not want to
> -	 * create a linear mapping for the memory like arch_add_memory()
> -	 * would do.
> -	 *
> -	 * For device public memory, which is accesible by the CPU, we do
> -	 * want the linear mapping and thus use arch_add_memory().
> -	 */
> -	if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
> -		ret = arch_add_memory(nid, align_start, align_size, NULL,
> -				false);
> -	else
> -		ret = add_pages(nid, align_start >> PAGE_SHIFT,
> -				align_size >> PAGE_SHIFT, NULL, false);
> -	if (ret) {
> -		mem_hotplug_done();
> -		goto error_add_memory;
> -	}
> -	move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
> -				align_start >> PAGE_SHIFT,
> -				align_size >> PAGE_SHIFT, NULL);
> -	mem_hotplug_done();
> -
> -	for (pfn = devmem->pfn_first; pfn < devmem->pfn_last; pfn++) {
> -		struct page *page = pfn_to_page(pfn);
> -
> -		page->pgmap = &devmem->pagemap;
> -	}
> -	return 0;
> -
> -error_add_memory:
> -	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
> -error_radix:
> -	hmm_devmem_radix_release(devmem->resource);
> -error:
> -	return ret;
> -}
> -
>  /*
>   * hmm_devmem_add() - hotplug ZONE_DEVICE memory for device memory
>   *
> @@ -1140,6 +993,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  {
>  	struct hmm_devmem *devmem;
>  	resource_size_t addr;
> +	void *result;
>  	int ret;
>  
>  	dev_pagemap_get_ops();
> @@ -1194,14 +1048,18 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
>  	devmem->pfn_last = devmem->pfn_first +
>  			   (resource_size(devmem->resource) >> PAGE_SHIFT);
>  
> -	ret = hmm_devmem_pages_create(devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> +	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> +	devmem->pagemap.res = *devmem->resource;
> +	devmem->pagemap.page_fault = hmm_devmem_fault;
> +	devmem->pagemap.page_free = hmm_devmem_free;
> +	devmem->pagemap.altmap_valid = false;
> +	devmem->pagemap.ref = &devmem->ref;
> +	devmem->pagemap.data = devmem;
>  
> +	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
> +			hmm_devmem_ref_kill);
> +	if (IS_ERR(result))
> +		return result;
>  	return devmem;
>  }
>  EXPORT_SYMBOL(hmm_devmem_add);
> @@ -1211,6 +1069,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  					   struct resource *res)
>  {
>  	struct hmm_devmem *devmem;
> +	void *result;
>  	int ret;
>  
>  	if (res->desc != IORES_DESC_DEVICE_PUBLIC_MEMORY)
> @@ -1243,19 +1102,18 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,
>  	devmem->pfn_last = devmem->pfn_first +
>  			   (resource_size(devmem->resource) >> PAGE_SHIFT);
>  
> -	ret = hmm_devmem_pages_create(devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_release, devmem);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
> -	ret = devm_add_action_or_reset(device, hmm_devmem_ref_kill,
> -			&devmem->ref);
> -	if (ret)
> -		return ERR_PTR(ret);
> +	devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;
> +	devmem->pagemap.res = *devmem->resource;
> +	devmem->pagemap.page_fault = hmm_devmem_fault;
> +	devmem->pagemap.page_free = hmm_devmem_free;
> +	devmem->pagemap.altmap_valid = false;
> +	devmem->pagemap.ref = &devmem->ref;
> +	devmem->pagemap.data = devmem;
>  
> +	result = devm_memremap_pages(devmem->device, &devmem->pagemap,
> +			hmm_devmem_ref_kill);
> +	if (IS_ERR(result))
> +		return result;
>  	return devmem;
>  }
>  EXPORT_SYMBOL(hmm_devmem_add_resource);
> 

Re: [PATCH v5 6/7] mm, hmm: Replace hmm_devmem_pages_create() with devm_memremap_pages()

[Balbir Singh]

On Wed, Sep 12, 2018 at 07:22:33PM -0700, Dan Williams wrote:
> Commit e8d513483300 "memremap: change devm_memremap_pages interface to
> use struct dev_pagemap" refactored devm_memremap_pages() to allow a
> dev_pagemap instance to be supplied. Passing in a dev_pagemap interface
> simplifies the design of pgmap type drivers in that they can rely on
> container_of() to lookup any private data associated with the given
> dev_pagemap instance.
> 
> In addition to the cleanups this also gives hmm users multi-order-radix
> improvements that arrived with commit ab1b597ee0e4 "mm,
> devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups"
> 
> As part of the conversion to the devm_memremap_pages() method of
> handling the percpu_ref relative to when pages are put, the percpu_ref
> completion needs to move to hmm_devmem_ref_exit(). See commit
> 71389703839e ("mm, zone_device: Replace {get, put}_zone_device_page...")
> for details.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Cc: "Jérôme Glisse" <jglisse@redhat.com>
> Cc: Logan Gunthorpe <logang@deltatee.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---

Looks like a good cleanup

Acked-by: Balbir Singh <bsingharora@gmail.com>