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Subject[PATCH 3/5] mm, hmm: use devm semantics for hmm_devmem_{add, remove}
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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.

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>
---
Documentation/vm/hmm.txt | 1
include/linux/hmm.h | 4 -
mm/hmm.c | 127 +++++++++++-----------------------------------
3 files changed, 32 insertions(+), 100 deletions(-)

diff --git a/Documentation/vm/hmm.txt b/Documentation/vm/hmm.txt
index 2d1d6f69e91b..b2f944b87c5e 100644
--- a/Documentation/vm/hmm.txt
+++ b/Documentation/vm/hmm.txt
@@ -285,7 +285,6 @@ region needing a struct page. This is offered through a very simple API:
struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
struct device *device,
unsigned long size);
- void hmm_devmem_remove(struct hmm_devmem *devmem);

The hmm_devmem_ops is where most of the important things are:

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 39988924de3a..880f6bb9485c 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 486dc394a5a3..8aa9d9fbb87b 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -993,15 +993,17 @@ 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 device *dev = devmem->device;
struct resource *resource = devmem->resource;
+ struct dev_pagemap *pgmap = &devmem->pagemap;
unsigned long start_pfn, npages;
struct zone *zone;
struct page *page;

- if (percpu_ref_tryget_live(&devmem->ref)) {
+ if (pgmap->registered && percpu_ref_tryget_live(&devmem->ref)) {
dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
percpu_ref_put(&devmem->ref);
}
@@ -1129,19 +1131,6 @@ 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
*
@@ -1169,8 +1158,7 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,

static_branch_enable(&device_private_key);

- 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);

@@ -1184,11 +1172,11 @@ 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,
@@ -1208,16 +1196,12 @@ 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;
@@ -1226,28 +1210,18 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,

ret = hmm_devmem_pages_create(devmem);
if (ret)
- goto error_pages;
+ 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);
+ devmem->pagemap.registered = true;

- 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_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);

@@ -1263,8 +1237,7 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops,

static_branch_enable(&device_private_key);

- 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);

@@ -1278,12 +1251,12 @@ 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 +
@@ -1291,60 +1264,22 @@ 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);
+ devmem->pagemap.registered = true;

- 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
* and it is not needed to make use of any HMM functionality.
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