Re: [PATCH 13/22] device-dax: use the dev_pagemap internal refcount

Ira Weiny
2019-06-14T00:20:57Z

On Thu, Jun 13, 2019 at 11:43:16AM +0200, Christoph Hellwig wrote:
> The functionality is identical to the one currently open coded in
> device-dax.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/dax/dax-private.h | 4 ---
> drivers/dax/device.c | 52 +--------------------------------------
> 2 files changed, 1 insertion(+), 55 deletions(-)
>
> diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
> index a45612148ca0..ed04a18a35be 100644
> --- a/drivers/dax/dax-private.h
> +++ b/drivers/dax/dax-private.h
> @@ -51,8 +51,6 @@ struct dax_region {
> * @target_node: effective numa node if dev_dax memory range is onlined
> * @dev - device core
> * @pgmap - pgmap for memmap setup / lifetime (driver owned)
> - * @ref: pgmap reference count (driver owned)
> - * @cmp: @ref final put completion (driver owned)
> */
> struct dev_dax {
> struct dax_region *region;
> @@ -60,8 +58,6 @@ struct dev_dax {
> int target_node;
> struct device dev;
> struct dev_pagemap pgmap;
> - struct percpu_ref ref;
> - struct completion cmp;
> };
>
> static inline struct dev_dax *to_dev_dax(struct device *dev)
> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> index e23fa1bd8c97..a9d7c90ecf1e 100644
> --- a/drivers/dax/device.c
> +++ b/drivers/dax/device.c
> @@ -14,37 +14,6 @@
> #include "dax-private.h"
> #include "bus.h"
>
> -static struct dev_dax *ref_to_dev_dax(struct percpu_ref *ref)
> -{
> - return container_of(ref, struct dev_dax, ref);
> -}
> -
> -static void dev_dax_percpu_release(struct percpu_ref *ref)
> -{
> - struct dev_dax *dev_dax = ref_to_dev_dax(ref);
> -
> - dev_dbg(&dev_dax->dev, "%s\n", __func__);
> - complete(&dev_dax->cmp);
> -}
> -
> -static void dev_dax_percpu_exit(void *data)
> -{
> - struct percpu_ref *ref = data;
> - struct dev_dax *dev_dax = ref_to_dev_dax(ref);
> -
> - dev_dbg(&dev_dax->dev, "%s\n", __func__);
> - wait_for_completion(&dev_dax->cmp);
> - percpu_ref_exit(ref);
> -}
> -
> -static void dev_dax_percpu_kill(struct dev_pagemap *pgmap)
> -{
> - struct dev_dax *dev_dax = container_of(pgmap, struct dev_dax, pgmap);
> -
> - dev_dbg(&dev_dax->dev, "%s\n", __func__);
> - percpu_ref_kill(pgmap->ref);
> -}
> -
> static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
> const char *func)
> {
> @@ -442,10 +411,6 @@ static void dev_dax_kill(void *dev_dax)
> kill_dev_dax(dev_dax);
> }
>
> -static const struct dev_pagemap_ops dev_dax_pagemap_ops = {
> - .kill = dev_dax_percpu_kill,
> -};
> -
> int dev_dax_probe(struct device *dev)
> {
> struct dev_dax *dev_dax = to_dev_dax(dev);
> @@ -463,24 +428,9 @@ int dev_dax_probe(struct device *dev)
> return -EBUSY;
> }
>
> - init_completion(&dev_dax->cmp);
> - rc = percpu_ref_init(&dev_dax->ref, dev_dax_percpu_release, 0,
> - GFP_KERNEL);
> - if (rc)
> - return rc;
> -
> - rc = devm_add_action_or_reset(dev, dev_dax_percpu_exit, &dev_dax->ref);
> - if (rc)
> - return rc;
> -
> - dev_dax->pgmap.ref = &dev_dax->ref;

I don't think this exactly correct. pgmap.ref is a pointer to the dev_dax ref
structure. Taking it away will cause devm_memremap_pages() to fail AFAICS.

I think you need to change struct dev_pagemap as well:

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index f0628660d541..5e2120589ddf 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -90,7 +90,7 @@ struct dev_pagemap {
struct vmem_altmap altmap;
bool altmap_valid;
struct resource res;
- struct percpu_ref *ref;
+ struct percpu_ref ref;
void (*kill)(struct percpu_ref *ref);
struct device *dev;
void *data;

And all usages of it, right?

Ira

> - dev_dax->pgmap.ops = &dev_dax_pagemap_ops;
> addr = devm_memremap_pages(dev, &dev_dax->pgmap);
> - if (IS_ERR(addr)) {
> - devm_remove_action(dev, dev_dax_percpu_exit, &dev_dax->ref);
> - percpu_ref_exit(&dev_dax->ref);
> + if (IS_ERR(addr))
> return PTR_ERR(addr);
> - }
>
> inode = dax_inode(dax_dev);
> cdev = inode->i_cdev;
> --
> 2.20.1
>
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