[PATCH 12/22] memremap: provide an optional internal refcount in struct dev_pagemap

Christoph Hellwig
2019-06-13T09:44:07Z

Provide an internal refcounting logic if no ->ref field is provided
in the pagemap passed into devm_memremap_pages so that callers don't
have to reinvent it poorly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
include/linux/memremap.h | 4 +++
kernel/memremap.c | 60 ++++++++++++++++++++++++++-----
tools/testing/nvdimm/test/iomap.c | 9 +++--
3 files changed, 62 insertions(+), 11 deletions(-)

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 75b80de6394a..b77ed00851ce 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -88,6 +88,8 @@ struct dev_pagemap_ops {
* @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
+ * @internal_ref: internal reference if @ref is not provided by the caller
+ * @done: completion for @internal_ref
* @dev: host device of the mapping for debug
* @data: private data pointer for page_free()
* @type: memory type: see MEMORY_* in memory_hotplug.h
@@ -98,6 +100,8 @@ struct dev_pagemap {
bool altmap_valid;
struct resource res;
struct percpu_ref *ref;
+ struct percpu_ref internal_ref;
+ struct completion done;
struct device *dev;
enum memory_type type;
u64 pci_p2pdma_bus_offset;
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 5c94ad4f5783..edca4389da68 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -83,6 +83,14 @@ static unsigned long pfn_next(unsigned long pfn)
#define for_each_device_pfn(pfn, map) \
for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))

+static void dev_pagemap_kill(struct dev_pagemap *pgmap)
+{
+ if (pgmap->ops && pgmap->ops->kill)
+ pgmap->ops->kill(pgmap);
+ else
+ percpu_ref_kill(pgmap->ref);
+}
+
static void devm_memremap_pages_release(void *data)
{
struct dev_pagemap *pgmap = data;
@@ -92,7 +100,8 @@ static void devm_memremap_pages_release(void *data)
unsigned long pfn;
int nid;

- pgmap->ops->kill(pgmap);
+ dev_pagemap_kill(pgmap);
+
for_each_device_pfn(pfn, pgmap)
put_page(pfn_to_page(pfn));

@@ -121,20 +130,37 @@ static void devm_memremap_pages_release(void *data)
"%s: failed to free all reserved pages\n", __func__);
}

+static void dev_pagemap_percpu_release(struct percpu_ref *ref)
+{
+ struct dev_pagemap *pgmap =
+ container_of(ref, struct dev_pagemap, internal_ref);
+
+ complete(&pgmap->done);
+}
+
+static void dev_pagemap_percpu_exit(void *data)
+{
+ struct dev_pagemap *pgmap = data;
+
+ wait_for_completion(&pgmap->done);
+ percpu_ref_exit(pgmap->ref);
+}
+
/**
* devm_memremap_pages - remap and provide memmap backing for the given resource
* @dev: hosting device for @res
* @pgmap: pointer to a struct dev_pagemap
*
* Notes:
- * 1/ At a minimum the res, ref and type and ops members of @pgmap must be
- * initialized by the caller before passing it to this function
+ * 1/ At a minimum the res and type members of @pgmap must be initialized
+ * by the caller before passing it to this function
*
* 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 will be killed at
- * devm_memremap_pages_release() time, or if this routine fails.
+ * 3/ The ref field may optionally be provided, in which 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
@@ -156,10 +182,26 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
pgprot_t pgprot = PAGE_KERNEL;
int error, nid, is_ram;

- if (!pgmap->ref || !pgmap->ops || !pgmap->ops->kill)
- return ERR_PTR(-EINVAL);
+ if (!pgmap->ref) {
+ if (pgmap->ops && pgmap->ops->kill)
+ return ERR_PTR(-EINVAL);
+
+ init_completion(&pgmap->done);
+ error = percpu_ref_init(&pgmap->internal_ref,
+ dev_pagemap_percpu_release, 0, GFP_KERNEL);
+ if (error)
+ return ERR_PTR(error);
+ pgmap->ref = &pgmap->internal_ref;
+ error = devm_add_action_or_reset(dev, dev_pagemap_percpu_exit,
+ pgmap);
+ if (error)
+ return ERR_PTR(error);
+ } else {
+ if (!pgmap->ops || !pgmap->ops->kill)
+ return ERR_PTR(-EINVAL);
+ }

- if (pgmap->ops->page_free) {
+ if (pgmap->ops && pgmap->ops->page_free) {
error = dev_pagemap_enable(dev);
if (error)
return ERR_PTR(error);
@@ -272,7 +314,7 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
err_pfn_remap:
pgmap_array_delete(res);
err_array:
- pgmap->ops->kill(pgmap);
+ dev_pagemap_kill(pgmap);
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 ee07c4de2b35..3d0e916f9fff 100644
--- a/tools/testing/nvdimm/test/iomap.c
+++ b/tools/testing/nvdimm/test/iomap.c
@@ -104,9 +104,14 @@ void *__wrap_devm_memremap(struct device *dev, resource_size_t offset,
}
EXPORT_SYMBOL(__wrap_devm_memremap);

-static void nfit_test_kill(void *pgmap)
+static void nfit_test_kill(void *data)
{
- pgmap->ops->kill(pgmap);
+ struct dev_pagemap *pgmap = data;
+
+ if (pgmap->ops && pgmap->ops->kill)
+ pgmap->ops->kill(pgmap);
+ else
+ percpu_ref_kill(pgmap->ref);
}

void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
--
2.20.1