Re: [PATCH 15/25] memremap: provide an optional internal refcount in struct dev_pagemap

Ira Weiny
2019-06-26T21:47:51Z

On Wed, Jun 26, 2019 at 02:27:14PM +0200, Christoph Hellwig wrote:
> 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 | 64 ++++++++++++++++++++++++-------
> tools/testing/nvdimm/test/iomap.c | 58 ++++++++++++++++++++++------
> 3 files changed, 101 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index e25685b878e9..f8a5b2a19945 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -95,6 +95,8 @@ 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
> @@ -105,6 +107,8 @@ struct dev_pagemap {
> struct vmem_altmap altmap;
> struct resource res;
> struct percpu_ref *ref;
> + struct percpu_ref internal_ref;
> + struct completion done;
> struct device *dev;
> enum memory_type type;
> unsigned int flags;
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index eee490e7d7e1..bea6f887adad 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -29,7 +29,7 @@ static void devmap_managed_enable_put(void *data)
>
> static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgmap)
> {
> - if (!pgmap->ops->page_free) {
> + if (!pgmap->ops || !pgmap->ops->page_free) {
> WARN(1, "Missing page_free method\n");
> return -EINVAL;
> }
> @@ -75,6 +75,24 @@ 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 dev_pagemap_cleanup(struct dev_pagemap *pgmap)
> +{
> + if (pgmap->ops && pgmap->ops->cleanup) {
> + pgmap->ops->cleanup(pgmap);
> + } else {
> + wait_for_completion(&pgmap->done);
> + percpu_ref_exit(pgmap->ref);
> + }
> +}
> +
> static void devm_memremap_pages_release(void *data)
> {
> struct dev_pagemap *pgmap = data;
> @@ -84,10 +102,10 @@ 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));
> - pgmap->ops->cleanup(pgmap);
> + dev_pagemap_cleanup(pgmap);
>
> /* pages are dead and unused, undo the arch mapping */
> align_start = res->start & ~(SECTION_SIZE - 1);
> @@ -114,20 +132,29 @@ 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);
> +}
> +
> /**
> * 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
> * PGMAP_ALTMAP_VALID must be set in pgmap->flags.
> *
> - * 3/ pgmap->ref must be 'live' on entry and will be killed and reaped
> - * 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 and reaped 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
> @@ -175,10 +202,21 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> break;
> }
>
> - if (!pgmap->ref || !pgmap->ops || !pgmap->ops->kill ||
> - !pgmap->ops->cleanup) {
> - WARN(1, "Missing reference count teardown definition\n");
> - return ERR_PTR(-EINVAL);
> + if (!pgmap->ref) {
> + if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
> + 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;
> + } else {
> + if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
> + WARN(1, "Missing reference count teardown definition\n");
> + return ERR_PTR(-EINVAL);
> + }

After this series are there any users who continue to supply their own
reference object and these callbacks?

As it stands:

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> }
>
> if (need_devmap_managed) {
> @@ -296,8 +334,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> err_pfn_remap:
> pgmap_array_delete(res);
> err_array:
> - pgmap->ops->kill(pgmap);
> - pgmap->ops->cleanup(pgmap);
> + dev_pagemap_kill(pgmap);
> + dev_pagemap_cleanup(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 82f901569e06..cd040b5abffe 100644
> --- a/tools/testing/nvdimm/test/iomap.c
> +++ b/tools/testing/nvdimm/test/iomap.c
> @@ -100,26 +100,60 @@ static void nfit_test_kill(void *_pgmap)
> {
> struct dev_pagemap *pgmap = _pgmap;
>
> - WARN_ON(!pgmap || !pgmap->ref || !pgmap->ops || !pgmap->ops->kill ||
> - !pgmap->ops->cleanup);
> - pgmap->ops->kill(pgmap);
> - pgmap->ops->cleanup(pgmap);
> + WARN_ON(!pgmap || !pgmap->ref);
> +
> + if (pgmap->ops && pgmap->ops->kill)
> + pgmap->ops->kill(pgmap);
> + else
> + percpu_ref_kill(pgmap->ref);
> +
> + if (pgmap->ops && pgmap->ops->cleanup) {
> + pgmap->ops->cleanup(pgmap);
> + } else {
> + wait_for_completion(&pgmap->done);
> + percpu_ref_exit(pgmap->ref);
> + }
> +}
> +
> +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);
> }
>
> void *__wrap_devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
> {
> + int error;
> resource_size_t offset = pgmap->res.start;
> struct nfit_test_resource *nfit_res = get_nfit_res(offset);
>
> - if (nfit_res) {
> - int rc;
> -
> - 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;
> + if (!nfit_res)
> + return devm_memremap_pages(dev, pgmap);
> +
> + pgmap->dev = dev;
> + if (!pgmap->ref) {
> + if (pgmap->ops && (pgmap->ops->kill || pgmap->ops->cleanup))
> + 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;
> + } else {
> + if (!pgmap->ops || !pgmap->ops->kill || !pgmap->ops->cleanup) {
> + WARN(1, "Missing reference count teardown definition\n");
> + return ERR_PTR(-EINVAL);
> + }
> }
> - return devm_memremap_pages(dev, pgmap);
> +
> + error = devm_add_action_or_reset(dev, nfit_test_kill, pgmap);
> + if (error)
> + return ERR_PTR(error);
> + return nfit_res->buf + offset - nfit_res->res.start;
> }
> EXPORT_SYMBOL_GPL(__wrap_devm_memremap_pages);
>
> --
> 2.20.1
>
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