Re: [PATCH] dma-buf: add reference counting for exporter module

Hi Tomasz,

Thanks for the patch.

On Wednesday 08 August 2012 12:17:41 Tomasz Stanislawski wrote:

This patch adds reference counting on a module that exports dma-buf and implements its operations. This prevents the module from being unloaded while DMABUF file is in use.

Signed-off-by: Tomasz Stanislawski t.stanislaws@samsung.com

Documentation/dma-buf-sharing.txt | 3 ++- drivers/base/dma-buf.c | 10 +++++++++- drivers/gpu/drm/exynos/exynos_drm_dmabuf.c | 1 + drivers/gpu/drm/i915/i915_gem_dmabuf.c | 1 + drivers/gpu/drm/nouveau/nouveau_prime.c | 1 + drivers/gpu/drm/radeon/radeon_prime.c | 1 + drivers/staging/omapdrm/omap_gem_dmabuf.c | 1 + include/linux/dma-buf.h | 2 ++ 8 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index ad86fb8..2613057 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -49,7 +49,8 @@ The dma_buf buffer sharing API usage contains the following steps: The buffer exporter announces its wish to export a buffer. In this, it connects its own private buffer data, provides implementation for operations that can be performed on the exported dma_buf, and flags for the file

• associated with this buffer.

• associated with this buffer. The operations structure has owner field.

• You should initialize this to THIS_MODULE in most cases.

  Interface: struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index c30f3e1..d14b2f5 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -27,6 +27,7 @@ #include <linux/dma-buf.h> #include <linux/anon_inodes.h> #include <linux/export.h> +#include <linux/module.h>

static inline int is_dma_buf_file(struct file *);

@@ -40,6 +41,7 @@ static int dma_buf_release(struct inode *inode, struct file *file) dmabuf = file->private_data;

dmabuf->ops->release(dmabuf);

• module_put(dmabuf->ops->owner); kfree(dmabuf); return 0;

} @@ -96,6 +98,7 @@ struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops, struct file *file;

if (WARN_ON(!priv || !ops

• 	  || !ops->owner
  

THIS_MODULE is defined as ((struct module *)0) when the driver is built-in, this check should thus be removed.

	  || !ops->map_dma_buf
	  || !ops->unmap_dma_buf
	  || !ops->release

@@ -105,9 +108,14 @@ struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops, return ERR_PTR(-EINVAL); }

• if (!try_module_get(ops->owner))

• return ERR_PTR(-ENOENT);
  

• dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);

• if (dmabuf == NULL)

• if (dmabuf == NULL) {

• module_put(ops->owner);
  

  return ERR_PTR(-ENOMEM);

• }

  dmabuf->priv = priv; dmabuf->ops = ops;

diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c index 613bf8a..cf3bc6d 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c @@ -164,6 +164,7 @@ static void exynos_gem_dmabuf_kunmap(struct dma_buf *dma_buf, }

static struct dma_buf_ops exynos_dmabuf_ops = {

• .owner = THIS_MODULE, .map_dma_buf = exynos_gem_map_dma_buf, .unmap_dma_buf = exynos_gem_unmap_dma_buf, .kmap = exynos_gem_dmabuf_kmap,

diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c index aa308e1..07ff03b 100644 --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c @@ -152,6 +152,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct * }

static const struct dma_buf_ops i915_dmabuf_ops = {

• .owner = THIS_MODULE, .map_dma_buf = i915_gem_map_dma_buf, .unmap_dma_buf = i915_gem_unmap_dma_buf, .release = i915_gem_dmabuf_release,

diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c b/drivers/gpu/drm/nouveau/nouveau_prime.c index a25cf2c..8605033 100644 --- a/drivers/gpu/drm/nouveau/nouveau_prime.c +++ b/drivers/gpu/drm/nouveau/nouveau_prime.c @@ -127,6 +127,7 @@ static void nouveau_gem_prime_vunmap(struct dma_buf *dma_buf, void *vaddr) }

static const struct dma_buf_ops nouveau_dmabuf_ops = {

• .owner = THIS_MODULE, .map_dma_buf = nouveau_gem_map_dma_buf, .unmap_dma_buf = nouveau_gem_unmap_dma_buf, .release = nouveau_gem_dmabuf_release,

diff --git a/drivers/gpu/drm/radeon/radeon_prime.c b/drivers/gpu/drm/radeon/radeon_prime.c index 6bef46a..4061fd3 100644 --- a/drivers/gpu/drm/radeon/radeon_prime.c +++ b/drivers/gpu/drm/radeon/radeon_prime.c @@ -127,6 +127,7 @@ static void radeon_gem_prime_vunmap(struct dma_buf *dma_buf, void *vaddr) mutex_unlock(&dev->struct_mutex); } const static struct dma_buf_ops radeon_dmabuf_ops = {

• .owner = THIS_MODULE, .map_dma_buf = radeon_gem_map_dma_buf, .unmap_dma_buf = radeon_gem_unmap_dma_buf, .release = radeon_gem_dmabuf_release,

diff --git a/drivers/staging/omapdrm/omap_gem_dmabuf.c b/drivers/staging/omapdrm/omap_gem_dmabuf.c index 42728e0..6a4dd67 100644 --- a/drivers/staging/omapdrm/omap_gem_dmabuf.c +++ b/drivers/staging/omapdrm/omap_gem_dmabuf.c @@ -179,6 +179,7 @@ out_unlock: }

struct dma_buf_ops omap_dmabuf_ops = {

• .owner = THIS_MODULE,
  

  .map_dma_buf = omap_gem_map_dma_buf, .unmap_dma_buf = omap_gem_unmap_dma_buf, .release = omap_gem_dmabuf_release,

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index eb48f38..22953de 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -37,6 +37,7 @@ struct dma_buf_attachment;

/**

• struct dma_buf_ops - operations possible on struct dma_buf

• • @owner: the module that implements dma_buf operations
  • @attach: [optional] allows different devices to 'attach' themselves to

the * given buffer. It might return -EBUSY to signal that backing storage * is already allocated and incompatible with the requirements @@ -70,6 +71,7 @@ struct dma_buf_attachment;

• @vunmap: [optional] unmaps a vmap from the buffer

*/ struct dma_buf_ops {

• struct module *owner; int (*attach)(struct dma_buf *, struct device *, struct dma_buf_attachment *);