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Subject[PATCH] driver core/platform: don't leak memory allocated for dma_mask
Date
If a dma_mask is provided as part of platform_device_info,
platform_device_register_full() allocate memory for a u64
using kmalloc().

A comment in the code state that "[t]his memory isn't freed
when the device is put".

It's never a good thing to leak memory, but there's only very
few users of platform_device_info's dma_mask, and those are mostly
"static" devices that are not going to be plugged/unplugged.

So memory leak is not really an issue, but allocating 8 bytes
through kmalloc() seems overkill, so this patch moves dma_mask
after the platform_device struct, dynamically allocated along
the name buffer.

With dma_mask part of the memory allocated for the platform_device
struct, like name buffer, it will be released with it:
no memory leak, no small allocation.

The draw back is the additional code needed to handle
dma_mask allocation:

Before:
text data bss dec hex filename
5927 532 32 6491 195b obj-i386/drivers/base/platform.o
7038 960 48 8046 1f6e obj-x86_64/drivers/base/platform.o

After:
text data bss dec hex filename
6007 532 32 6571 19ab obj-i386/drivers/base/platform.o
7134 960 48 8142 1fce obj-x86_64/drivers/base/platform.o

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
---
drivers/base/platform.c | 93 +++++++++++++++++++++++++++++++++++--------------
1 file changed, 67 insertions(+), 26 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 3a94b799f166..95f4cbafe1d7 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -157,7 +157,7 @@ EXPORT_SYMBOL_GPL(platform_add_devices);

struct platform_object {
struct platform_device pdev;
- char name[1];
+ char payload[0];
};

/**
@@ -186,6 +186,25 @@ static void platform_device_release(struct device *dev)
kfree(pa);
}

+static struct platform_object *platform_object_alloc(size_t payload)
+{
+ struct platform_object *pa;
+
+ pa = kzalloc(sizeof(*pa) + payload, GFP_KERNEL);
+
+ return pa;
+}
+
+static void platform_object_init(struct platform_object *pa,
+ const char *name, int id)
+{
+ pa->pdev.name = name;
+ pa->pdev.id = id;
+ device_initialize(&pa->pdev.dev);
+ pa->pdev.dev.release = platform_device_release;
+ arch_setup_pdev_archdata(&pa->pdev);
+}
+
/**
* platform_device_alloc - create a platform device
* @name: base name of the device we're adding
@@ -198,14 +217,10 @@ struct platform_device *platform_device_alloc(const char *name, int id)
{
struct platform_object *pa;

- pa = kzalloc(sizeof(struct platform_object) + strlen(name), GFP_KERNEL);
+ pa = platform_object_alloc(strlen(name) + 1);
if (pa) {
- strcpy(pa->name, name);
- pa->pdev.name = pa->name;
- pa->pdev.id = id;
- device_initialize(&pa->pdev.dev);
- pa->pdev.dev.release = platform_device_release;
- arch_setup_pdev_archdata(&pa->pdev);
+ strcpy(pa->payload, name);
+ platform_object_init(pa, pa->payload, id);
}

return pa ? &pa->pdev : NULL;
@@ -213,6 +228,38 @@ struct platform_device *platform_device_alloc(const char *name, int id)
EXPORT_SYMBOL_GPL(platform_device_alloc);

/**
+ * platform_device_dmamask_alloc - create a platform device suitable to hold a dmamask
+ * @name: base name of the device we're adding
+ * @id: instance id
+ *
+ * Create a platform device object which can have other objects attached
+ * to it, and which will have attached objects freed when it is released.
+ */
+static struct platform_device *platform_device_dmamask_alloc(const char *name,
+ int id)
+{
+ struct platform_object *pa;
+ const size_t padding = (((offsetof(struct platform_object, payload) +
+ (__alignof__(u64) - 1)) &
+ ~(__alignof__(u64) - 1)) -
+ offsetof(struct platform_object, payload));
+
+ pa = platform_object_alloc(padding + sizeof(u64) + strlen(name) + 1);
+ if (pa) {
+ char *payload = pa->payload + padding;
+ strcpy(payload + sizeof(u64), name);
+ /*
+ * Conceptually dma_mask in struct device should not be a pointer.
+ * See http://thread.gmane.org/gmane.linux.kernel.pci/9081
+ */
+ pa->pdev.dev.dma_mask = (void *)payload;
+ platform_object_init(pa, payload + sizeof(u64), id);
+ }
+
+ return pa ? &pa->pdev : NULL;
+}
+
+/**
* platform_device_add_resources - add resources to a platform device
* @pdev: platform device allocated by platform_device_alloc to add resources to
* @res: set of resources that needs to be allocated for the device
@@ -427,29 +474,23 @@ struct platform_device *platform_device_register_full(
int ret = -ENOMEM;
struct platform_device *pdev;

- pdev = platform_device_alloc(pdevinfo->name, pdevinfo->id);
- if (!pdev)
- goto err_alloc;
-
- pdev->dev.parent = pdevinfo->parent;
- ACPI_COMPANION_SET(&pdev->dev, pdevinfo->acpi_node.companion);
-
- if (pdevinfo->dma_mask) {
- /*
- * This memory isn't freed when the device is put,
- * I don't have a nice idea for that though. Conceptually
- * dma_mask in struct device should not be a pointer.
- * See http://thread.gmane.org/gmane.linux.kernel.pci/9081
- */
- pdev->dev.dma_mask =
- kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
- if (!pdev->dev.dma_mask)
- goto err;
+ if (!pdevinfo->dma_mask) {
+ pdev = platform_device_alloc(pdevinfo->name, pdevinfo->id);
+ if (!pdev)
+ goto err_alloc;
+ } else {
+ pdev = platform_device_dmamask_alloc(pdevinfo->name,
+ pdevinfo->id);
+ if (!pdev)
+ goto err_alloc;

*pdev->dev.dma_mask = pdevinfo->dma_mask;
pdev->dev.coherent_dma_mask = pdevinfo->dma_mask;
}

+ pdev->dev.parent = pdevinfo->parent;
+ ACPI_COMPANION_SET(&pdev->dev, pdevinfo->acpi_node.companion);
+
ret = platform_device_add_resources(pdev,
pdevinfo->res, pdevinfo->num_res);
if (ret)
--
1.8.4.2


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