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authorLinus Torvalds <torvalds@linux-foundation.org>2013-02-28 19:43:13 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-28 19:43:13 -0800
commit5e04f4b4290e03deb91b074087ae8d7c169d947d (patch)
tree07802848a6afce236de7c3185be06db8567b38f0
parentb6669737d3db7df79fad07180837c23dbe581db5 (diff)
parent495c10cc1c0c359871d5bef32dd173252fc17995 (diff)
downloadvexpress-lsk-5e04f4b4290e03deb91b074087ae8d7c169d947d.tar.gz
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
-rw-r--r--Documentation/dma-buf-sharing.txt6
-rw-r--r--drivers/base/dma-buf.c66
-rw-r--r--include/linux/dma-buf.h4
3 files changed, 63 insertions, 13 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt
index 0188903bc9e..4966b1be42a 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 ff5b745c470..2a7cb0df176 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 3d754a394e9..9978b614a1a 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;
};