Merge tag 'tag-for-linus-3.9' of git://git.linaro.org/people/sumitsemwal/linux-dma-buf

Pull dma-buf framework updates from Sumit Semwal:
 "Refcounting implemented for vmap in core dma-buf"

* tag 'tag-for-linus-3.9' of git://git.linaro.org/people/sumitsemwal/linux-dma-buf:
  CHROMIUM: dma-buf: restore args on failure of dma_buf_mmap
  dma-buf: implement vmap refcounting in the interface logic

3 files changed, 63 insertions, 13 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..2a7cb0df176b 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;
@@ -445,6 +447,9 @@ EXPORT_SYMBOL_GPL(dma_buf_kunmap);
 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
                  unsigned long pgoff)
 {
+        struct file *oldfile;
+        int ret;
+
         if (WARN_ON(!dmabuf || !vma))
                 return -EINVAL;
 
@@ -458,14 +463,22 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
                 return -EINVAL;
 
         /* readjust the vma */
-        if (vma->vm_file)
-                fput(vma->vm_file);
-
-        vma->vm_file = get_file(dmabuf->file);
-
+        get_file(dmabuf->file);
+        oldfile = vma->vm_file;
+        vma->vm_file = dmabuf->file;
         vma->vm_pgoff = pgoff;
 
-        return dmabuf->ops->mmap(dmabuf, vma);
+        ret = dmabuf->ops->mmap(dmabuf, vma);
+        if (ret) {
+                /* restore old parameters on failure */
+                vma->vm_file = oldfile;
+                fput(dmabuf->file);
+        } else {
+                if (oldfile)
+                        fput(oldfile);
+        }
+        return ret;
+
 }
 EXPORT_SYMBOL_GPL(dma_buf_mmap);
 
@@ -481,12 +494,34 @@ 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 +535,16 @@ 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;
 };