Commit 8021fa16 authored by Dmitry Osipenko's avatar Dmitry Osipenko
Browse files

dma-buf: Change locking policy for mmap() 



Change locking policy of mmap() callback, making exporters responsible
for handling dma-buf reservation locking. Previous locking policy stated
that dma-buf is locked for both importers and exporters by the dma-buf
core, which caused a deadlock problem for DRM drivers in a case of
self-imported dma-bufs which required to take the lock from the DRM
exporter side.

Acked-by: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: default avatarDmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230529223935.2672495-6-dmitry.osipenko@collabora.com
parent 11f38236

drivers/dma-buf/dma-buf.c

+3 −14
Original line number Diff line number Diff line
@@ -131,7 +131,6 @@ static struct file_system_type dma_buf_fs_type = { 
static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)

{

	struct dma_buf *dmabuf;

	int ret;



	if (!is_dma_buf_file(file))

		return -EINVAL;
@@ -147,11 +146,7 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) 
	    dmabuf->size >> PAGE_SHIFT)

		return -EINVAL;



	dma_resv_lock(dmabuf->resv, NULL);

	ret = dmabuf->ops->mmap(dmabuf, vma);

	dma_resv_unlock(dmabuf->resv);



	return ret;

	return dmabuf->ops->mmap(dmabuf, vma);

}



static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
@@ -850,6 +845,7 @@ static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach, 
 *     - &dma_buf_ops.release()

 *     - &dma_buf_ops.begin_cpu_access()

 *     - &dma_buf_ops.end_cpu_access()

 *     - &dma_buf_ops.mmap()

 *

 * 2. These &dma_buf_ops callbacks are invoked with locked dma-buf

 *    reservation and exporter can't take the lock:
@@ -858,7 +854,6 @@ static struct sg_table * __map_dma_buf(struct dma_buf_attachment *attach, 
 *     - &dma_buf_ops.unpin()

 *     - &dma_buf_ops.map_dma_buf()

 *     - &dma_buf_ops.unmap_dma_buf()

 *     - &dma_buf_ops.mmap()

 *     - &dma_buf_ops.vmap()

 *     - &dma_buf_ops.vunmap()

 *
@@ -1463,8 +1458,6 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF); 
int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,

		 unsigned long pgoff)

{

	int ret;



	if (WARN_ON(!dmabuf || !vma))

		return -EINVAL;
@@ -1485,11 +1478,7 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma, 
	vma_set_file(vma, dmabuf->file);

	vma->vm_pgoff = pgoff;



	dma_resv_lock(dmabuf->resv, NULL);

	ret = dmabuf->ops->mmap(dmabuf, vma);

	dma_resv_unlock(dmabuf->resv);



	return ret;

	return dmabuf->ops->mmap(dmabuf, vma);

}

EXPORT_SYMBOL_NS_GPL(dma_buf_mmap, DMA_BUF);