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

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