Am 28.06.2018 um 11:53 schrieb Zhang, Jerry (Junwei):

On 06/22/2018 10:11 PM, Christian König wrote:

...

Add function variants which can be called with the reservation lock already held.

v2: reordered, add lockdep asserts, fix kerneldoc

Signed-off-by: Christian König christian.koenig@amd.com

drivers/dma-buf/dma-buf.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++   include/linux/dma-buf.h   |  5 +++++   2 files changed, 62 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 852a3928ee71..dc94e76e2e2a 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -606,6 +606,40 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)   }   EXPORT_SYMBOL_GPL(dma_buf_detach);

+/**

• • dma_buf_map_attachment_locked - Maps the buffer into _device_

address space

• • with the reservation lock held. Is a wrapper for map_dma_buf() of

the

• • Returns the scatterlist table of the attachment;
• • dma_buf_ops.
• • @attach:    [in]    attachment whose scatterlist is to be returned
• • @direction:    [in]    direction of DMA transfer
• • Returns sg_table containing the scatterlist to be returned;

returns ERR_PTR

• • on error. May return -EINTR if it is interrupted by a signal.
• • A mapping must be unmapped by using

dma_buf_unmap_attachment_locked(). Note

• • that the underlying backing storage is pinned for as long as a

mapping

• • exists, therefore users/importers should not hold onto a mapping

for undue

• • amounts of time.
• */

+struct sg_table * +dma_buf_map_attachment_locked(struct dma_buf_attachment *attach, +                  enum dma_data_direction direction) +{ +    struct sg_table *sg_table;

Perhaps better to add some error check, like dma_buf_map_attachment()

WARN_ON(!attach || !attach->dmabuf)

Actually I wanted to remove those from the other functions as well.

WARN_ON and BUG_ON checks for NULL pointers before using them are totally pointless because they have the same effect as a crash.

Regards, Christian.

Apart from that, it's Reviewed-by: Junwei Zhang Jerry.Zhang@amd.com

Jerry

...

+    might_sleep(); +    reservation_object_assert_held(attach->dmabuf->resv);

+    sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction); +    if (!sg_table) +        sg_table = ERR_PTR(-ENOMEM);

+    return sg_table; +} +EXPORT_SYMBOL_GPL(dma_buf_map_attachment_locked);

/**    * dma_buf_map_attachment - Returns the scatterlist table of the attachment;    * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the @@ -639,6 +673,29 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,   }   EXPORT_SYMBOL_GPL(dma_buf_map_attachment);

+/**

• • dma_buf_unmap_attachment_locked - unmaps the buffer with

reservation lock

• • held, should deallocate the associated scatterlist. Is a wrapper for
• • unmap_dma_buf() of dma_buf_ops.
• • @attach:    [in]    attachment to unmap buffer from
• • @sg_table:    [in]    scatterlist info of the buffer to unmap
• • @direction:  [in]    direction of DMA transfer
• • This unmaps a DMA mapping for @attached obtained by
• • dma_buf_map_attachment_locked().
• */

+void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *attach, +                     struct sg_table *sg_table, +                     enum dma_data_direction direction) +{ +    might_sleep(); +    reservation_object_assert_held(attach->dmabuf->resv);

+    attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, +                        direction); +} +EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment_locked);

/**    * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might    * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 991787a03199..a25e754ae2f7 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -384,8 +384,13 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags);   struct dma_buf *dma_buf_get(int fd);   void dma_buf_put(struct dma_buf *dmabuf);

+struct sg_table *dma_buf_map_attachment_locked(struct dma_buf_attachment *, +                           enum dma_data_direction);   struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *,                       enum dma_data_direction); +void dma_buf_unmap_attachment_locked(struct dma_buf_attachment *, +                     struct sg_table *, +                     enum dma_data_direction);   void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,                   enum dma_data_direction);   int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,