diff options
| -rw-r--r-- | Documentation/dma-buf-sharing.txt | 6 | ||||
| -rw-r--r-- | drivers/base/dma-buf.c | 43 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 4 |
3 files changed, 46 insertions, 7 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 0188903bc9e1..4966b1be42ac 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -302,7 +302,11 @@ Access to a dma_buf from the kernel context involves three steps: void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) The vmap call can fail if there is no vmap support in the exporter, or if it - runs out of vmalloc space. Fallback to kmap should be implemented. + runs out of vmalloc space. Fallback to kmap should be implemented. Note that + the dma-buf layer keeps a reference count for all vmap access and calls down + into the exporter's vmap function only when no vmapping exists, and only + unmaps it once. Protection against concurrent vmap/vunmap calls is provided + by taking the dma_buf->lock mutex. 3. Finish access diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index ff5b745c4705..394523807a6d 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -39,6 +39,8 @@ static int dma_buf_release(struct inode *inode, struct file *file) dmabuf = file->private_data; + BUG_ON(dmabuf->vmapping_counter); + dmabuf->ops->release(dmabuf); kfree(dmabuf); return 0; @@ -481,12 +483,34 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap); */ void *dma_buf_vmap(struct dma_buf *dmabuf) { + void *ptr; + if (WARN_ON(!dmabuf)) return NULL; - if (dmabuf->ops->vmap) - return dmabuf->ops->vmap(dmabuf); - return NULL; + if (!dmabuf->ops->vmap) + return NULL; + + mutex_lock(&dmabuf->lock); + if (dmabuf->vmapping_counter) { + dmabuf->vmapping_counter++; + BUG_ON(!dmabuf->vmap_ptr); + ptr = dmabuf->vmap_ptr; + goto out_unlock; + } + + BUG_ON(dmabuf->vmap_ptr); + + ptr = dmabuf->ops->vmap(dmabuf); + if (IS_ERR_OR_NULL(ptr)) + goto out_unlock; + + dmabuf->vmap_ptr = ptr; + dmabuf->vmapping_counter = 1; + +out_unlock: + mutex_unlock(&dmabuf->lock); + return ptr; } EXPORT_SYMBOL_GPL(dma_buf_vmap); @@ -500,7 +524,16 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) if (WARN_ON(!dmabuf)) return; - if (dmabuf->ops->vunmap) - dmabuf->ops->vunmap(dmabuf, vaddr); + BUG_ON(!dmabuf->vmap_ptr); + BUG_ON(dmabuf->vmapping_counter == 0); + BUG_ON(dmabuf->vmap_ptr != vaddr); + + mutex_lock(&dmabuf->lock); + if (--dmabuf->vmapping_counter == 0) { + if (dmabuf->ops->vunmap) + dmabuf->ops->vunmap(dmabuf, vaddr); + dmabuf->vmap_ptr = NULL; + } + mutex_unlock(&dmabuf->lock); } EXPORT_SYMBOL_GPL(dma_buf_vunmap); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 3d754a394e92..9978b614a1aa 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -119,8 +119,10 @@ struct dma_buf { struct file *file; struct list_head attachments; const struct dma_buf_ops *ops; - /* mutex to serialize list manipulation and attach/detach */ + /* mutex to serialize list manipulation, attach/detach and vmap/unmap */ struct mutex lock; + unsigned vmapping_counter; + void *vmap_ptr; void *priv; }; |