[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

dma_buf_map_attachment and dma_buf_vmap can return NULL or
ERR_PTR on a error.  This encourages a common buggy pattern in
callers:
	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
	if (IS_ERR_OR_NULL(sgt))
                return PTR_ERR(sgt);

This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
is almost always a sign of poorly-defined error handling.

This patch converts dma_buf_map_attachment to always return
ERR_PTR, and fixes the callers that incorrectly handled NULL.
There are a few more callers that were not checking for NULL
at all, which would have dereferenced a NULL pointer later.
There are also a few more callers that correctly handled NULL
and ERR_PTR differently, I left those alone but they could also
be modified to delete the NULL check.

This patch also converts dma_buf_vmap to always return NULL.
All the callers to dma_buf_vmap only check for NULL, and would
have dereferenced an ERR_PTR and panic'd if one was ever
returned. This is not consistent with the rest of the dma buf
APIs, but matches the expectations of all of the callers.

Signed-off-by: Colin Cross <ccross@android.com>
---
 drivers/base/dma-buf.c                         | 18 +++++++++++-------
 drivers/gpu/drm/drm_prime.c                    |  2 +-
 drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
 drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 1e16cbd61da2..cfe1d8bc7bb8 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
  * @dmabuf:	[in]	buffer to attach device to.
  * @dev:	[in]	device to be attached.
  *
- * Returns struct dma_buf_attachment * for this attachment; may return negative
- * error codes.
- *
+ * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
+ * error.
  */
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 					  struct device *dev)
@@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
  * @attach:	[in]	attachment whose scatterlist is to be returned
  * @direction:	[in]	direction of DMA transfer
  *
- * Returns sg_table containing the scatterlist to be returned; may return NULL
- * or ERR_PTR.
- *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error.
  */
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 					enum dma_data_direction direction)
@@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 		return ERR_PTR(-EINVAL);
 
 	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		sg_table = ERR_PTR(-ENOMEM);
 
 	return sg_table;
 }
@@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
  * These calls are optional in drivers. The intended use for them
  * is for mapping objects linear in kernel space for high use objects.
  * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
  */
 void *dma_buf_vmap(struct dma_buf *dmabuf)
 {
@@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
 	BUG_ON(dmabuf->vmap_ptr);
 
 	ptr = dmabuf->ops->vmap(dmabuf);
-	if (IS_ERR_OR_NULL(ptr))
+	if (WARN_ON_ONCE(IS_ERR(ptr)))
+		ptr = NULL;
+	if (!ptr)
 		goto out_unlock;
 
 	dmabuf->vmap_ptr = ptr;
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 56805c39c906..bb516fdd195d 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto fail_detach;
 	}
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
index 59827cc5e770..c786cd4f457b 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
@@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto err_buf_detach;
 	}
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 33d3871d1e13..880be0782dd9 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
 
 	/* get the associated scatterlist for this buffer */
 	sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		pr_err("Error getting dmabuf scatterlist\n");
 		return -EINVAL;
 	}
-- 
1.8.5.1

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

dma_buf_map_attachment and dma_buf_vmap can return NULL or
ERR_PTR on a error.  This encourages a common buggy pattern in
callers:
	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
	if (IS_ERR_OR_NULL(sgt))
                return PTR_ERR(sgt);

This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
is almost always a sign of poorly-defined error handling.

This patch converts dma_buf_map_attachment to always return
ERR_PTR, and fixes the callers that incorrectly handled NULL.
There are a few more callers that were not checking for NULL
at all, which would have dereferenced a NULL pointer later.
There are also a few more callers that correctly handled NULL
and ERR_PTR differently, I left those alone but they could also
be modified to delete the NULL check.

This patch also converts dma_buf_vmap to always return NULL.
All the callers to dma_buf_vmap only check for NULL, and would
have dereferenced an ERR_PTR and panic'd if one was ever
returned. This is not consistent with the rest of the dma buf
APIs, but matches the expectations of all of the callers.

Signed-off-by: Colin Cross <ccross@android.com>
---
 drivers/base/dma-buf.c                         | 18 +++++++++++-------
 drivers/gpu/drm/drm_prime.c                    |  2 +-
 drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
 drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 1e16cbd61da2..cfe1d8bc7bb8 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
  * @dmabuf:	[in]	buffer to attach device to.
  * @dev:	[in]	device to be attached.
  *
- * Returns struct dma_buf_attachment * for this attachment; may return negative
- * error codes.
- *
+ * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
+ * error.
  */
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 					  struct device *dev)
@@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
  * @attach:	[in]	attachment whose scatterlist is to be returned
  * @direction:	[in]	direction of DMA transfer
  *
- * Returns sg_table containing the scatterlist to be returned; may return NULL
- * or ERR_PTR.
- *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error.
  */
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 					enum dma_data_direction direction)
@@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 		return ERR_PTR(-EINVAL);
 
 	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		sg_table = ERR_PTR(-ENOMEM);
 
 	return sg_table;
 }
@@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
  * These calls are optional in drivers. The intended use for them
  * is for mapping objects linear in kernel space for high use objects.
  * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
  */
 void *dma_buf_vmap(struct dma_buf *dmabuf)
 {
@@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
 	BUG_ON(dmabuf->vmap_ptr);
 
 	ptr = dmabuf->ops->vmap(dmabuf);
-	if (IS_ERR_OR_NULL(ptr))
+	if (WARN_ON_ONCE(IS_ERR(ptr)))
+		ptr = NULL;
+	if (!ptr)
 		goto out_unlock;
 
 	dmabuf->vmap_ptr = ptr;
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 56805c39c906..bb516fdd195d 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto fail_detach;
 	}
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
index 59827cc5e770..c786cd4f457b 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
@@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto err_buf_detach;
 	}
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 33d3871d1e13..880be0782dd9 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
 
 	/* get the associated scatterlist for this buffer */
 	sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		pr_err("Error getting dmabuf scatterlist\n");
 		return -EINVAL;
 	}
-- 
1.8.5.1

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

dma_buf_map_attachment and dma_buf_vmap can return NULL or
ERR_PTR on a error.  This encourages a common buggy pattern in
callers:
	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
	if (IS_ERR_OR_NULL(sgt))
                return PTR_ERR(sgt);

This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
is almost always a sign of poorly-defined error handling.

This patch converts dma_buf_map_attachment to always return
ERR_PTR, and fixes the callers that incorrectly handled NULL.
There are a few more callers that were not checking for NULL
at all, which would have dereferenced a NULL pointer later.
There are also a few more callers that correctly handled NULL
and ERR_PTR differently, I left those alone but they could also
be modified to delete the NULL check.

This patch also converts dma_buf_vmap to always return NULL.
All the callers to dma_buf_vmap only check for NULL, and would
have dereferenced an ERR_PTR and panic'd if one was ever
returned. This is not consistent with the rest of the dma buf
APIs, but matches the expectations of all of the callers.

Signed-off-by: Colin Cross <ccross@android.com>
---
 drivers/base/dma-buf.c                         | 18 +++++++++++-------
 drivers/gpu/drm/drm_prime.c                    |  2 +-
 drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
 drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 1e16cbd61da2..cfe1d8bc7bb8 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
  * @dmabuf:	[in]	buffer to attach device to.
  * @dev:	[in]	device to be attached.
  *
- * Returns struct dma_buf_attachment * for this attachment; may return negative
- * error codes.
- *
+ * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
+ * error.
  */
 struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
 					  struct device *dev)
@@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
  * @attach:	[in]	attachment whose scatterlist is to be returned
  * @direction:	[in]	direction of DMA transfer
  *
- * Returns sg_table containing the scatterlist to be returned; may return NULL
- * or ERR_PTR.
- *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error.
  */
 struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 					enum dma_data_direction direction)
@@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
 		return ERR_PTR(-EINVAL);
 
 	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		sg_table = ERR_PTR(-ENOMEM);
 
 	return sg_table;
 }
@@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
  * These calls are optional in drivers. The intended use for them
  * is for mapping objects linear in kernel space for high use objects.
  * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
  */
 void *dma_buf_vmap(struct dma_buf *dmabuf)
 {
@@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
 	BUG_ON(dmabuf->vmap_ptr);
 
 	ptr = dmabuf->ops->vmap(dmabuf);
-	if (IS_ERR_OR_NULL(ptr))
+	if (WARN_ON_ONCE(IS_ERR(ptr)))
+		ptr = NULL;
+	if (!ptr)
 		goto out_unlock;
 
 	dmabuf->vmap_ptr = ptr;
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 56805c39c906..bb516fdd195d 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto fail_detach;
 	}
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
index 59827cc5e770..c786cd4f457b 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
@@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
 	get_dma_buf(dma_buf);
 
 	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		ret = PTR_ERR(sgt);
 		goto err_buf_detach;
 	}
diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 33d3871d1e13..880be0782dd9 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
 
 	/* get the associated scatterlist for this buffer */
 	sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
-	if (IS_ERR_OR_NULL(sgt)) {
+	if (IS_ERR(sgt)) {
 		pr_err("Error getting dmabuf scatterlist\n");
 		return -EINVAL;
 	}
-- 
1.8.5.1

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Rob Clark]

On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> dma_buf_map_attachment and dma_buf_vmap can return NULL or
> ERR_PTR on a error.  This encourages a common buggy pattern in
> callers:
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>         if (IS_ERR_OR_NULL(sgt))
>                 return PTR_ERR(sgt);
>
> This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> is almost always a sign of poorly-defined error handling.
>
> This patch converts dma_buf_map_attachment to always return
> ERR_PTR, and fixes the callers that incorrectly handled NULL.
> There are a few more callers that were not checking for NULL
> at all, which would have dereferenced a NULL pointer later.
> There are also a few more callers that correctly handled NULL
> and ERR_PTR differently, I left those alone but they could also
> be modified to delete the NULL check.
>
> This patch also converts dma_buf_vmap to always return NULL.
> All the callers to dma_buf_vmap only check for NULL, and would
> have dereferenced an ERR_PTR and panic'd if one was ever
> returned. This is not consistent with the rest of the dma buf
> APIs, but matches the expectations of all of the callers.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> ---
>  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>  drivers/gpu/drm/drm_prime.c                    |  2 +-
>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>  4 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 1e16cbd61da2..cfe1d8bc7bb8 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>   * @dmabuf:    [in]    buffer to attach device to.
>   * @dev:       [in]    device to be attached.
>   *
> - * Returns struct dma_buf_attachment * for this attachment; may return negative
> - * error codes.
> - *
> + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> + * error.
>   */
>  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>                                           struct device *dev)
> @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>   * @attach:    [in]    attachment whose scatterlist is to be returned
>   * @direction: [in]    direction of DMA transfer
>   *
> - * Returns sg_table containing the scatterlist to be returned; may return NULL
> - * or ERR_PTR.
> - *
> + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> + * on error.
>   */
>  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                                         enum dma_data_direction direction)
> @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                 return ERR_PTR(-EINVAL);
>
>         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> +       if (!sg_table)
> +               sg_table = ERR_PTR(-ENOMEM);
>
>         return sg_table;
>  }
> @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>   * These calls are optional in drivers. The intended use for them
>   * is for mapping objects linear in kernel space for high use objects.
>   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> + *
> + * Returns NULL on error.
>   */
>  void *dma_buf_vmap(struct dma_buf *dmabuf)
>  {
> @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>         BUG_ON(dmabuf->vmap_ptr);
>
>         ptr = dmabuf->ops->vmap(dmabuf);
> -       if (IS_ERR_OR_NULL(ptr))
> +       if (WARN_ON_ONCE(IS_ERR(ptr)))

since vmap is optional, the WARN_ON might be a bit strong..  although
it would be a bit strange for an exporter to supply a vmap fxn which
always returned NULL, not sure about that.  Just thought I'd mention
it in case anyone else had an opinion about that.

But either way:

Reviewed-by: Rob Clark <robdclark@gmail.com>


> +               ptr = NULL;
> +       if (!ptr)
>                 goto out_unlock;
>
>         dmabuf->vmap_ptr = ptr;
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 56805c39c906..bb516fdd195d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto fail_detach;
>         }
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> index 59827cc5e770..c786cd4f457b 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto err_buf_detach;
>         }
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index 33d3871d1e13..880be0782dd9 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
>
>         /* get the associated scatterlist for this buffer */
>         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 pr_err("Error getting dmabuf scatterlist\n");
>                 return -EINVAL;
>         }
> --
> 1.8.5.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Rob Clark]

On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> dma_buf_map_attachment and dma_buf_vmap can return NULL or
> ERR_PTR on a error.  This encourages a common buggy pattern in
> callers:
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>         if (IS_ERR_OR_NULL(sgt))
>                 return PTR_ERR(sgt);
>
> This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> is almost always a sign of poorly-defined error handling.
>
> This patch converts dma_buf_map_attachment to always return
> ERR_PTR, and fixes the callers that incorrectly handled NULL.
> There are a few more callers that were not checking for NULL
> at all, which would have dereferenced a NULL pointer later.
> There are also a few more callers that correctly handled NULL
> and ERR_PTR differently, I left those alone but they could also
> be modified to delete the NULL check.
>
> This patch also converts dma_buf_vmap to always return NULL.
> All the callers to dma_buf_vmap only check for NULL, and would
> have dereferenced an ERR_PTR and panic'd if one was ever
> returned. This is not consistent with the rest of the dma buf
> APIs, but matches the expectations of all of the callers.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> ---
>  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>  drivers/gpu/drm/drm_prime.c                    |  2 +-
>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>  4 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 1e16cbd61da2..cfe1d8bc7bb8 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>   * @dmabuf:    [in]    buffer to attach device to.
>   * @dev:       [in]    device to be attached.
>   *
> - * Returns struct dma_buf_attachment * for this attachment; may return negative
> - * error codes.
> - *
> + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> + * error.
>   */
>  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>                                           struct device *dev)
> @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>   * @attach:    [in]    attachment whose scatterlist is to be returned
>   * @direction: [in]    direction of DMA transfer
>   *
> - * Returns sg_table containing the scatterlist to be returned; may return NULL
> - * or ERR_PTR.
> - *
> + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> + * on error.
>   */
>  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                                         enum dma_data_direction direction)
> @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                 return ERR_PTR(-EINVAL);
>
>         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> +       if (!sg_table)
> +               sg_table = ERR_PTR(-ENOMEM);
>
>         return sg_table;
>  }
> @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>   * These calls are optional in drivers. The intended use for them
>   * is for mapping objects linear in kernel space for high use objects.
>   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> + *
> + * Returns NULL on error.
>   */
>  void *dma_buf_vmap(struct dma_buf *dmabuf)
>  {
> @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>         BUG_ON(dmabuf->vmap_ptr);
>
>         ptr = dmabuf->ops->vmap(dmabuf);
> -       if (IS_ERR_OR_NULL(ptr))
> +       if (WARN_ON_ONCE(IS_ERR(ptr)))

since vmap is optional, the WARN_ON might be a bit strong..  although
it would be a bit strange for an exporter to supply a vmap fxn which
always returned NULL, not sure about that.  Just thought I'd mention
it in case anyone else had an opinion about that.

But either way:

Reviewed-by: Rob Clark <robdclark@gmail.com>


> +               ptr = NULL;
> +       if (!ptr)
>                 goto out_unlock;
>
>         dmabuf->vmap_ptr = ptr;
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 56805c39c906..bb516fdd195d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto fail_detach;
>         }
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> index 59827cc5e770..c786cd4f457b 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto err_buf_detach;
>         }
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index 33d3871d1e13..880be0782dd9 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
>
>         /* get the associated scatterlist for this buffer */
>         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 pr_err("Error getting dmabuf scatterlist\n");
>                 return -EINVAL;
>         }
> --
> 1.8.5.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Rob Clark]

On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> dma_buf_map_attachment and dma_buf_vmap can return NULL or
> ERR_PTR on a error.  This encourages a common buggy pattern in
> callers:
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>         if (IS_ERR_OR_NULL(sgt))
>                 return PTR_ERR(sgt);
>
> This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> is almost always a sign of poorly-defined error handling.
>
> This patch converts dma_buf_map_attachment to always return
> ERR_PTR, and fixes the callers that incorrectly handled NULL.
> There are a few more callers that were not checking for NULL
> at all, which would have dereferenced a NULL pointer later.
> There are also a few more callers that correctly handled NULL
> and ERR_PTR differently, I left those alone but they could also
> be modified to delete the NULL check.
>
> This patch also converts dma_buf_vmap to always return NULL.
> All the callers to dma_buf_vmap only check for NULL, and would
> have dereferenced an ERR_PTR and panic'd if one was ever
> returned. This is not consistent with the rest of the dma buf
> APIs, but matches the expectations of all of the callers.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> ---
>  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>  drivers/gpu/drm/drm_prime.c                    |  2 +-
>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>  4 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 1e16cbd61da2..cfe1d8bc7bb8 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>   * @dmabuf:    [in]    buffer to attach device to.
>   * @dev:       [in]    device to be attached.
>   *
> - * Returns struct dma_buf_attachment * for this attachment; may return negative
> - * error codes.
> - *
> + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> + * error.
>   */
>  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>                                           struct device *dev)
> @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>   * @attach:    [in]    attachment whose scatterlist is to be returned
>   * @direction: [in]    direction of DMA transfer
>   *
> - * Returns sg_table containing the scatterlist to be returned; may return NULL
> - * or ERR_PTR.
> - *
> + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> + * on error.
>   */
>  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                                         enum dma_data_direction direction)
> @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                 return ERR_PTR(-EINVAL);
>
>         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> +       if (!sg_table)
> +               sg_table = ERR_PTR(-ENOMEM);
>
>         return sg_table;
>  }
> @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>   * These calls are optional in drivers. The intended use for them
>   * is for mapping objects linear in kernel space for high use objects.
>   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> + *
> + * Returns NULL on error.
>   */
>  void *dma_buf_vmap(struct dma_buf *dmabuf)
>  {
> @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>         BUG_ON(dmabuf->vmap_ptr);
>
>         ptr = dmabuf->ops->vmap(dmabuf);
> -       if (IS_ERR_OR_NULL(ptr))
> +       if (WARN_ON_ONCE(IS_ERR(ptr)))

since vmap is optional, the WARN_ON might be a bit strong..  although
it would be a bit strange for an exporter to supply a vmap fxn which
always returned NULL, not sure about that.  Just thought I'd mention
it in case anyone else had an opinion about that.

But either way:

Reviewed-by: Rob Clark <robdclark@gmail.com>


> +               ptr = NULL;
> +       if (!ptr)
>                 goto out_unlock;
>
>         dmabuf->vmap_ptr = ptr;
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 56805c39c906..bb516fdd195d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto fail_detach;
>         }
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> index 59827cc5e770..c786cd4f457b 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto err_buf_detach;
>         }
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index 33d3871d1e13..880be0782dd9 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
>
>         /* get the associated scatterlist for this buffer */
>         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 pr_err("Error getting dmabuf scatterlist\n");
>                 return -EINVAL;
>         }
> --
> 1.8.5.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Rob Clark]

On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> dma_buf_map_attachment and dma_buf_vmap can return NULL or
> ERR_PTR on a error.  This encourages a common buggy pattern in
> callers:
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>         if (IS_ERR_OR_NULL(sgt))
>                 return PTR_ERR(sgt);
>
> This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> is almost always a sign of poorly-defined error handling.
>
> This patch converts dma_buf_map_attachment to always return
> ERR_PTR, and fixes the callers that incorrectly handled NULL.
> There are a few more callers that were not checking for NULL
> at all, which would have dereferenced a NULL pointer later.
> There are also a few more callers that correctly handled NULL
> and ERR_PTR differently, I left those alone but they could also
> be modified to delete the NULL check.
>
> This patch also converts dma_buf_vmap to always return NULL.
> All the callers to dma_buf_vmap only check for NULL, and would
> have dereferenced an ERR_PTR and panic'd if one was ever
> returned. This is not consistent with the rest of the dma buf
> APIs, but matches the expectations of all of the callers.
>
> Signed-off-by: Colin Cross <ccross@android.com>
> ---
>  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>  drivers/gpu/drm/drm_prime.c                    |  2 +-
>  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>  4 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index 1e16cbd61da2..cfe1d8bc7bb8 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>   * @dmabuf:    [in]    buffer to attach device to.
>   * @dev:       [in]    device to be attached.
>   *
> - * Returns struct dma_buf_attachment * for this attachment; may return negative
> - * error codes.
> - *
> + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> + * error.
>   */
>  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>                                           struct device *dev)
> @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>   * @attach:    [in]    attachment whose scatterlist is to be returned
>   * @direction: [in]    direction of DMA transfer
>   *
> - * Returns sg_table containing the scatterlist to be returned; may return NULL
> - * or ERR_PTR.
> - *
> + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> + * on error.
>   */
>  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                                         enum dma_data_direction direction)
> @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>                 return ERR_PTR(-EINVAL);
>
>         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> +       if (!sg_table)
> +               sg_table = ERR_PTR(-ENOMEM);
>
>         return sg_table;
>  }
> @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>   * These calls are optional in drivers. The intended use for them
>   * is for mapping objects linear in kernel space for high use objects.
>   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> + *
> + * Returns NULL on error.
>   */
>  void *dma_buf_vmap(struct dma_buf *dmabuf)
>  {
> @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>         BUG_ON(dmabuf->vmap_ptr);
>
>         ptr = dmabuf->ops->vmap(dmabuf);
> -       if (IS_ERR_OR_NULL(ptr))
> +       if (WARN_ON_ONCE(IS_ERR(ptr)))

since vmap is optional, the WARN_ON might be a bit strong..  although
it would be a bit strange for an exporter to supply a vmap fxn which
always returned NULL, not sure about that.  Just thought I'd mention
it in case anyone else had an opinion about that.

But either way:

Reviewed-by: Rob Clark <robdclark@gmail.com>


> +               ptr = NULL;
> +       if (!ptr)
>                 goto out_unlock;
>
>         dmabuf->vmap_ptr = ptr;
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 56805c39c906..bb516fdd195d 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto fail_detach;
>         }
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> index 59827cc5e770..c786cd4f457b 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
>         get_dma_buf(dma_buf);
>
>         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 ret = PTR_ERR(sgt);
>                 goto err_buf_detach;
>         }
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> index 33d3871d1e13..880be0782dd9 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
>
>         /* get the associated scatterlist for this buffer */
>         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> -       if (IS_ERR_OR_NULL(sgt)) {
> +       if (IS_ERR(sgt)) {
>                 pr_err("Error getting dmabuf scatterlist\n");
>                 return -EINVAL;
>         }
> --
> 1.8.5.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Mauro Carvalho Chehab]

Em Sat, 21 Dec 2013 07:42:17 -0500
Rob Clark <robdclark@gmail.com> escreveu:

> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.
> 
> But either way:
> 
> Reviewed-by: Rob Clark <robdclark@gmail.com>

IMHO, a WARN_ON_ONCE() here (or some other error report printk) seems ok, 
as, if this function is called, the caller would be expecting it to not
fail.

Either way:

Reviewed-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

> 
> 
> > +               ptr = NULL;
> > +       if (!ptr)
> >                 goto out_unlock;
> >
> >         dmabuf->vmap_ptr = ptr;
> > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> > index 56805c39c906..bb516fdd195d 100644
> > --- a/drivers/gpu/drm/drm_prime.c
> > +++ b/drivers/gpu/drm/drm_prime.c
> > @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto fail_detach;
> >         }
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > index 59827cc5e770..c786cd4f457b 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto err_buf_detach;
> >         }
> > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > index 33d3871d1e13..880be0782dd9 100644
> > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
> >
> >         /* get the associated scatterlist for this buffer */
> >         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 pr_err("Error getting dmabuf scatterlist\n");
> >                 return -EINVAL;
> >         }
> > --
> > 1.8.5.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


-- 

Cheers,
Mauro

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Mauro Carvalho Chehab]

Em Sat, 21 Dec 2013 07:42:17 -0500
Rob Clark <robdclark@gmail.com> escreveu:

> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.
> 
> But either way:
> 
> Reviewed-by: Rob Clark <robdclark@gmail.com>

IMHO, a WARN_ON_ONCE() here (or some other error report printk) seems ok, 
as, if this function is called, the caller would be expecting it to not
fail.

Either way:

Reviewed-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

> 
> 
> > +               ptr = NULL;
> > +       if (!ptr)
> >                 goto out_unlock;
> >
> >         dmabuf->vmap_ptr = ptr;
> > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> > index 56805c39c906..bb516fdd195d 100644
> > --- a/drivers/gpu/drm/drm_prime.c
> > +++ b/drivers/gpu/drm/drm_prime.c
> > @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto fail_detach;
> >         }
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > index 59827cc5e770..c786cd4f457b 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto err_buf_detach;
> >         }
> > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > index 33d3871d1e13..880be0782dd9 100644
> > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
> >
> >         /* get the associated scatterlist for this buffer */
> >         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 pr_err("Error getting dmabuf scatterlist\n");
> >                 return -EINVAL;
> >         }
> > --
> > 1.8.5.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


-- 

Cheers,
Mauro

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Mauro Carvalho Chehab]

Em Sat, 21 Dec 2013 07:42:17 -0500
Rob Clark <robdclark@gmail.com> escreveu:

> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.
> 
> But either way:
> 
> Reviewed-by: Rob Clark <robdclark@gmail.com>

IMHO, a WARN_ON_ONCE() here (or some other error report printk) seems ok, 
as, if this function is called, the caller would be expecting it to not
fail.

Either way:

Reviewed-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

> 
> 
> > +               ptr = NULL;
> > +       if (!ptr)
> >                 goto out_unlock;
> >
> >         dmabuf->vmap_ptr = ptr;
> > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> > index 56805c39c906..bb516fdd195d 100644
> > --- a/drivers/gpu/drm/drm_prime.c
> > +++ b/drivers/gpu/drm/drm_prime.c
> > @@ -471,7 +471,7 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto fail_detach;
> >         }
> > diff --git a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > index 59827cc5e770..c786cd4f457b 100644
> > --- a/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > +++ b/drivers/gpu/drm/exynos/exynos_drm_dmabuf.c
> > @@ -224,7 +224,7 @@ struct drm_gem_object *exynos_dmabuf_prime_import(struct drm_device *drm_dev,
> >         get_dma_buf(dma_buf);
> >
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 ret = PTR_ERR(sgt);
> >                 goto err_buf_detach;
> >         }
> > diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > index 33d3871d1e13..880be0782dd9 100644
> > --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> > @@ -719,7 +719,7 @@ static int vb2_dc_map_dmabuf(void *mem_priv)
> >
> >         /* get the associated scatterlist for this buffer */
> >         sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
> > -       if (IS_ERR_OR_NULL(sgt)) {
> > +       if (IS_ERR(sgt)) {
> >                 pr_err("Error getting dmabuf scatterlist\n");
> >                 return -EINVAL;
> >         }
> > --
> > 1.8.5.1
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo at vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


-- 

Cheers,
Mauro

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.

Yeah, I don't like this, it could cause unnecessary reports of problems.

Care to fix it up?

thanks,

greg k-h

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.

Yeah, I don't like this, it could cause unnecessary reports of problems.

Care to fix it up?

thanks,

greg k-h

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> > ERR_PTR on a error.  This encourages a common buggy pattern in
> > callers:
> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >         if (IS_ERR_OR_NULL(sgt))
> >                 return PTR_ERR(sgt);
> >
> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> > is almost always a sign of poorly-defined error handling.
> >
> > This patch converts dma_buf_map_attachment to always return
> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> > There are a few more callers that were not checking for NULL
> > at all, which would have dereferenced a NULL pointer later.
> > There are also a few more callers that correctly handled NULL
> > and ERR_PTR differently, I left those alone but they could also
> > be modified to delete the NULL check.
> >
> > This patch also converts dma_buf_vmap to always return NULL.
> > All the callers to dma_buf_vmap only check for NULL, and would
> > have dereferenced an ERR_PTR and panic'd if one was ever
> > returned. This is not consistent with the rest of the dma buf
> > APIs, but matches the expectations of all of the callers.
> >
> > Signed-off-by: Colin Cross <ccross@android.com>
> > ---
> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> > --- a/drivers/base/dma-buf.c
> > +++ b/drivers/base/dma-buf.c
> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >   * @dmabuf:    [in]    buffer to attach device to.
> >   * @dev:       [in]    device to be attached.
> >   *
> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> > - * error codes.
> > - *
> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> > + * error.
> >   */
> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >                                           struct device *dev)
> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >   * @direction: [in]    direction of DMA transfer
> >   *
> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> > - * or ERR_PTR.
> > - *
> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> > + * on error.
> >   */
> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                                         enum dma_data_direction direction)
> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >                 return ERR_PTR(-EINVAL);
> >
> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> > +       if (!sg_table)
> > +               sg_table = ERR_PTR(-ENOMEM);
> >
> >         return sg_table;
> >  }
> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >   * These calls are optional in drivers. The intended use for them
> >   * is for mapping objects linear in kernel space for high use objects.
> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> > + *
> > + * Returns NULL on error.
> >   */
> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >  {
> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >         BUG_ON(dmabuf->vmap_ptr);
> >
> >         ptr = dmabuf->ops->vmap(dmabuf);
> > -       if (IS_ERR_OR_NULL(ptr))
> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> 
> since vmap is optional, the WARN_ON might be a bit strong..  although
> it would be a bit strange for an exporter to supply a vmap fxn which
> always returned NULL, not sure about that.  Just thought I'd mention
> it in case anyone else had an opinion about that.

Yeah, I don't like this, it could cause unnecessary reports of problems.

Care to fix it up?

thanks,

greg k-h

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
>> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
>> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
>> > ERR_PTR on a error.  This encourages a common buggy pattern in
>> > callers:
>> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>> >         if (IS_ERR_OR_NULL(sgt))
>> >                 return PTR_ERR(sgt);
>> >
>> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
>> > is almost always a sign of poorly-defined error handling.
>> >
>> > This patch converts dma_buf_map_attachment to always return
>> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
>> > There are a few more callers that were not checking for NULL
>> > at all, which would have dereferenced a NULL pointer later.
>> > There are also a few more callers that correctly handled NULL
>> > and ERR_PTR differently, I left those alone but they could also
>> > be modified to delete the NULL check.
>> >
>> > This patch also converts dma_buf_vmap to always return NULL.
>> > All the callers to dma_buf_vmap only check for NULL, and would
>> > have dereferenced an ERR_PTR and panic'd if one was ever
>> > returned. This is not consistent with the rest of the dma buf
>> > APIs, but matches the expectations of all of the callers.
>> >
>> > Signed-off-by: Colin Cross <ccross@android.com>
>> > ---
>> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
>> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>> >  4 files changed, 14 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
>> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
>> > --- a/drivers/base/dma-buf.c
>> > +++ b/drivers/base/dma-buf.c
>> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>> >   * @dmabuf:    [in]    buffer to attach device to.
>> >   * @dev:       [in]    device to be attached.
>> >   *
>> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
>> > - * error codes.
>> > - *
>> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
>> > + * error.
>> >   */
>> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>> >                                           struct device *dev)
>> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>> >   * @attach:    [in]    attachment whose scatterlist is to be returned
>> >   * @direction: [in]    direction of DMA transfer
>> >   *
>> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
>> > - * or ERR_PTR.
>> > - *
>> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
>> > + * on error.
>> >   */
>> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                                         enum dma_data_direction direction)
>> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                 return ERR_PTR(-EINVAL);
>> >
>> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
>> > +       if (!sg_table)
>> > +               sg_table = ERR_PTR(-ENOMEM);
>> >
>> >         return sg_table;
>> >  }
>> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>> >   * These calls are optional in drivers. The intended use for them
>> >   * is for mapping objects linear in kernel space for high use objects.
>> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
>> > + *
>> > + * Returns NULL on error.
>> >   */
>> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >  {
>> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >         BUG_ON(dmabuf->vmap_ptr);
>> >
>> >         ptr = dmabuf->ops->vmap(dmabuf);
>> > -       if (IS_ERR_OR_NULL(ptr))
>> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
>>
>> since vmap is optional, the WARN_ON might be a bit strong..  although
>> it would be a bit strange for an exporter to supply a vmap fxn which
>> always returned NULL, not sure about that.  Just thought I'd mention
>> it in case anyone else had an opinion about that.
>
> Yeah, I don't like this, it could cause unnecessary reports of problems.

The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
returns NULL.  This is designed to catch vmap ops that don't follow
the spec, so I would call them necessary reports, but I can take it
out if you still disagree.

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
>> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
>> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
>> > ERR_PTR on a error.  This encourages a common buggy pattern in
>> > callers:
>> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>> >         if (IS_ERR_OR_NULL(sgt))
>> >                 return PTR_ERR(sgt);
>> >
>> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
>> > is almost always a sign of poorly-defined error handling.
>> >
>> > This patch converts dma_buf_map_attachment to always return
>> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
>> > There are a few more callers that were not checking for NULL
>> > at all, which would have dereferenced a NULL pointer later.
>> > There are also a few more callers that correctly handled NULL
>> > and ERR_PTR differently, I left those alone but they could also
>> > be modified to delete the NULL check.
>> >
>> > This patch also converts dma_buf_vmap to always return NULL.
>> > All the callers to dma_buf_vmap only check for NULL, and would
>> > have dereferenced an ERR_PTR and panic'd if one was ever
>> > returned. This is not consistent with the rest of the dma buf
>> > APIs, but matches the expectations of all of the callers.
>> >
>> > Signed-off-by: Colin Cross <ccross@android.com>
>> > ---
>> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
>> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>> >  4 files changed, 14 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
>> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
>> > --- a/drivers/base/dma-buf.c
>> > +++ b/drivers/base/dma-buf.c
>> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>> >   * @dmabuf:    [in]    buffer to attach device to.
>> >   * @dev:       [in]    device to be attached.
>> >   *
>> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
>> > - * error codes.
>> > - *
>> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
>> > + * error.
>> >   */
>> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>> >                                           struct device *dev)
>> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>> >   * @attach:    [in]    attachment whose scatterlist is to be returned
>> >   * @direction: [in]    direction of DMA transfer
>> >   *
>> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
>> > - * or ERR_PTR.
>> > - *
>> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
>> > + * on error.
>> >   */
>> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                                         enum dma_data_direction direction)
>> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                 return ERR_PTR(-EINVAL);
>> >
>> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
>> > +       if (!sg_table)
>> > +               sg_table = ERR_PTR(-ENOMEM);
>> >
>> >         return sg_table;
>> >  }
>> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>> >   * These calls are optional in drivers. The intended use for them
>> >   * is for mapping objects linear in kernel space for high use objects.
>> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
>> > + *
>> > + * Returns NULL on error.
>> >   */
>> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >  {
>> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >         BUG_ON(dmabuf->vmap_ptr);
>> >
>> >         ptr = dmabuf->ops->vmap(dmabuf);
>> > -       if (IS_ERR_OR_NULL(ptr))
>> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
>>
>> since vmap is optional, the WARN_ON might be a bit strong..  although
>> it would be a bit strange for an exporter to supply a vmap fxn which
>> always returned NULL, not sure about that.  Just thought I'd mention
>> it in case anyone else had an opinion about that.
>
> Yeah, I don't like this, it could cause unnecessary reports of problems.

The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
returns NULL.  This is designed to catch vmap ops that don't follow
the spec, so I would call them necessary reports, but I can take it
out if you still disagree.

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Colin Cross]

On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
>> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
>> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
>> > ERR_PTR on a error.  This encourages a common buggy pattern in
>> > callers:
>> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
>> >         if (IS_ERR_OR_NULL(sgt))
>> >                 return PTR_ERR(sgt);
>> >
>> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
>> > is almost always a sign of poorly-defined error handling.
>> >
>> > This patch converts dma_buf_map_attachment to always return
>> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
>> > There are a few more callers that were not checking for NULL
>> > at all, which would have dereferenced a NULL pointer later.
>> > There are also a few more callers that correctly handled NULL
>> > and ERR_PTR differently, I left those alone but they could also
>> > be modified to delete the NULL check.
>> >
>> > This patch also converts dma_buf_vmap to always return NULL.
>> > All the callers to dma_buf_vmap only check for NULL, and would
>> > have dereferenced an ERR_PTR and panic'd if one was ever
>> > returned. This is not consistent with the rest of the dma buf
>> > APIs, but matches the expectations of all of the callers.
>> >
>> > Signed-off-by: Colin Cross <ccross@android.com>
>> > ---
>> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
>> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
>> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
>> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
>> >  4 files changed, 14 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
>> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
>> > --- a/drivers/base/dma-buf.c
>> > +++ b/drivers/base/dma-buf.c
>> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
>> >   * @dmabuf:    [in]    buffer to attach device to.
>> >   * @dev:       [in]    device to be attached.
>> >   *
>> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
>> > - * error codes.
>> > - *
>> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
>> > + * error.
>> >   */
>> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
>> >                                           struct device *dev)
>> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
>> >   * @attach:    [in]    attachment whose scatterlist is to be returned
>> >   * @direction: [in]    direction of DMA transfer
>> >   *
>> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
>> > - * or ERR_PTR.
>> > - *
>> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
>> > + * on error.
>> >   */
>> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                                         enum dma_data_direction direction)
>> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
>> >                 return ERR_PTR(-EINVAL);
>> >
>> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
>> > +       if (!sg_table)
>> > +               sg_table = ERR_PTR(-ENOMEM);
>> >
>> >         return sg_table;
>> >  }
>> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
>> >   * These calls are optional in drivers. The intended use for them
>> >   * is for mapping objects linear in kernel space for high use objects.
>> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
>> > + *
>> > + * Returns NULL on error.
>> >   */
>> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >  {
>> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
>> >         BUG_ON(dmabuf->vmap_ptr);
>> >
>> >         ptr = dmabuf->ops->vmap(dmabuf);
>> > -       if (IS_ERR_OR_NULL(ptr))
>> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
>>
>> since vmap is optional, the WARN_ON might be a bit strong..  although
>> it would be a bit strange for an exporter to supply a vmap fxn which
>> always returned NULL, not sure about that.  Just thought I'd mention
>> it in case anyone else had an opinion about that.
>
> Yeah, I don't like this, it could cause unnecessary reports of problems.

The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
returns NULL.  This is designed to catch vmap ops that don't follow
the spec, so I would call them necessary reports, but I can take it
out if you still disagree.

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Fri, Feb 07, 2014 at 09:22:37AM -0800, Colin Cross wrote:
> On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> >> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> >> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> >> > ERR_PTR on a error.  This encourages a common buggy pattern in
> >> > callers:
> >> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >> >         if (IS_ERR_OR_NULL(sgt))
> >> >                 return PTR_ERR(sgt);
> >> >
> >> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> >> > is almost always a sign of poorly-defined error handling.
> >> >
> >> > This patch converts dma_buf_map_attachment to always return
> >> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> >> > There are a few more callers that were not checking for NULL
> >> > at all, which would have dereferenced a NULL pointer later.
> >> > There are also a few more callers that correctly handled NULL
> >> > and ERR_PTR differently, I left those alone but they could also
> >> > be modified to delete the NULL check.
> >> >
> >> > This patch also converts dma_buf_vmap to always return NULL.
> >> > All the callers to dma_buf_vmap only check for NULL, and would
> >> > have dereferenced an ERR_PTR and panic'd if one was ever
> >> > returned. This is not consistent with the rest of the dma buf
> >> > APIs, but matches the expectations of all of the callers.
> >> >
> >> > Signed-off-by: Colin Cross <ccross@android.com>
> >> > ---
> >> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >> >
> >> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> >> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> >> > --- a/drivers/base/dma-buf.c
> >> > +++ b/drivers/base/dma-buf.c
> >> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >> >   * @dmabuf:    [in]    buffer to attach device to.
> >> >   * @dev:       [in]    device to be attached.
> >> >   *
> >> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> >> > - * error codes.
> >> > - *
> >> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> >> > + * error.
> >> >   */
> >> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >> >                                           struct device *dev)
> >> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >> >   * @direction: [in]    direction of DMA transfer
> >> >   *
> >> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> >> > - * or ERR_PTR.
> >> > - *
> >> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> >> > + * on error.
> >> >   */
> >> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                                         enum dma_data_direction direction)
> >> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                 return ERR_PTR(-EINVAL);
> >> >
> >> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> >> > +       if (!sg_table)
> >> > +               sg_table = ERR_PTR(-ENOMEM);
> >> >
> >> >         return sg_table;
> >> >  }
> >> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >> >   * These calls are optional in drivers. The intended use for them
> >> >   * is for mapping objects linear in kernel space for high use objects.
> >> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> >> > + *
> >> > + * Returns NULL on error.
> >> >   */
> >> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >  {
> >> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >         BUG_ON(dmabuf->vmap_ptr);
> >> >
> >> >         ptr = dmabuf->ops->vmap(dmabuf);
> >> > -       if (IS_ERR_OR_NULL(ptr))
> >> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> >>
> >> since vmap is optional, the WARN_ON might be a bit strong..  although
> >> it would be a bit strange for an exporter to supply a vmap fxn which
> >> always returned NULL, not sure about that.  Just thought I'd mention
> >> it in case anyone else had an opinion about that.
> >
> > Yeah, I don't like this, it could cause unnecessary reports of problems.
> 
> The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
> returns NULL.  This is designed to catch vmap ops that don't follow
> the spec, so I would call them necessary reports, but I can take it
> out if you still disagree.

Ah, ok, that makes more sense.  I'll queue this up.

thanks,

greg k-h

Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Fri, Feb 07, 2014 at 09:22:37AM -0800, Colin Cross wrote:
> On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> >> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> >> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> >> > ERR_PTR on a error.  This encourages a common buggy pattern in
> >> > callers:
> >> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >> >         if (IS_ERR_OR_NULL(sgt))
> >> >                 return PTR_ERR(sgt);
> >> >
> >> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> >> > is almost always a sign of poorly-defined error handling.
> >> >
> >> > This patch converts dma_buf_map_attachment to always return
> >> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> >> > There are a few more callers that were not checking for NULL
> >> > at all, which would have dereferenced a NULL pointer later.
> >> > There are also a few more callers that correctly handled NULL
> >> > and ERR_PTR differently, I left those alone but they could also
> >> > be modified to delete the NULL check.
> >> >
> >> > This patch also converts dma_buf_vmap to always return NULL.
> >> > All the callers to dma_buf_vmap only check for NULL, and would
> >> > have dereferenced an ERR_PTR and panic'd if one was ever
> >> > returned. This is not consistent with the rest of the dma buf
> >> > APIs, but matches the expectations of all of the callers.
> >> >
> >> > Signed-off-by: Colin Cross <ccross@android.com>
> >> > ---
> >> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >> >
> >> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> >> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> >> > --- a/drivers/base/dma-buf.c
> >> > +++ b/drivers/base/dma-buf.c
> >> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >> >   * @dmabuf:    [in]    buffer to attach device to.
> >> >   * @dev:       [in]    device to be attached.
> >> >   *
> >> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> >> > - * error codes.
> >> > - *
> >> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> >> > + * error.
> >> >   */
> >> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >> >                                           struct device *dev)
> >> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >> >   * @direction: [in]    direction of DMA transfer
> >> >   *
> >> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> >> > - * or ERR_PTR.
> >> > - *
> >> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> >> > + * on error.
> >> >   */
> >> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                                         enum dma_data_direction direction)
> >> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                 return ERR_PTR(-EINVAL);
> >> >
> >> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> >> > +       if (!sg_table)
> >> > +               sg_table = ERR_PTR(-ENOMEM);
> >> >
> >> >         return sg_table;
> >> >  }
> >> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >> >   * These calls are optional in drivers. The intended use for them
> >> >   * is for mapping objects linear in kernel space for high use objects.
> >> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> >> > + *
> >> > + * Returns NULL on error.
> >> >   */
> >> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >  {
> >> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >         BUG_ON(dmabuf->vmap_ptr);
> >> >
> >> >         ptr = dmabuf->ops->vmap(dmabuf);
> >> > -       if (IS_ERR_OR_NULL(ptr))
> >> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> >>
> >> since vmap is optional, the WARN_ON might be a bit strong..  although
> >> it would be a bit strange for an exporter to supply a vmap fxn which
> >> always returned NULL, not sure about that.  Just thought I'd mention
> >> it in case anyone else had an opinion about that.
> >
> > Yeah, I don't like this, it could cause unnecessary reports of problems.
> 
> The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
> returns NULL.  This is designed to catch vmap ops that don't follow
> the spec, so I would call them necessary reports, but I can take it
> out if you still disagree.

Ah, ok, that makes more sense.  I'll queue this up.

thanks,

greg k-h

[PATCH] dma-buf: avoid using IS_ERR_OR_NULL

[Greg Kroah-Hartman]

On Fri, Feb 07, 2014 at 09:22:37AM -0800, Colin Cross wrote:
> On Fri, Feb 7, 2014 at 8:43 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote:
> >> On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross <ccross@android.com> wrote:
> >> > dma_buf_map_attachment and dma_buf_vmap can return NULL or
> >> > ERR_PTR on a error.  This encourages a common buggy pattern in
> >> > callers:
> >> >         sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
> >> >         if (IS_ERR_OR_NULL(sgt))
> >> >                 return PTR_ERR(sgt);
> >> >
> >> > This causes the caller to return 0 on an error.  IS_ERR_OR_NULL
> >> > is almost always a sign of poorly-defined error handling.
> >> >
> >> > This patch converts dma_buf_map_attachment to always return
> >> > ERR_PTR, and fixes the callers that incorrectly handled NULL.
> >> > There are a few more callers that were not checking for NULL
> >> > at all, which would have dereferenced a NULL pointer later.
> >> > There are also a few more callers that correctly handled NULL
> >> > and ERR_PTR differently, I left those alone but they could also
> >> > be modified to delete the NULL check.
> >> >
> >> > This patch also converts dma_buf_vmap to always return NULL.
> >> > All the callers to dma_buf_vmap only check for NULL, and would
> >> > have dereferenced an ERR_PTR and panic'd if one was ever
> >> > returned. This is not consistent with the rest of the dma buf
> >> > APIs, but matches the expectations of all of the callers.
> >> >
> >> > Signed-off-by: Colin Cross <ccross@android.com>
> >> > ---
> >> >  drivers/base/dma-buf.c                         | 18 +++++++++++-------
> >> >  drivers/gpu/drm/drm_prime.c                    |  2 +-
> >> >  drivers/gpu/drm/exynos/exynos_drm_dmabuf.c     |  2 +-
> >> >  drivers/media/v4l2-core/videobuf2-dma-contig.c |  2 +-
> >> >  4 files changed, 14 insertions(+), 10 deletions(-)
> >> >
> >> > diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> >> > index 1e16cbd61da2..cfe1d8bc7bb8 100644
> >> > --- a/drivers/base/dma-buf.c
> >> > +++ b/drivers/base/dma-buf.c
> >> > @@ -251,9 +251,8 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> >> >   * @dmabuf:    [in]    buffer to attach device to.
> >> >   * @dev:       [in]    device to be attached.
> >> >   *
> >> > - * Returns struct dma_buf_attachment * for this attachment; may return negative
> >> > - * error codes.
> >> > - *
> >> > + * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
> >> > + * error.
> >> >   */
> >> >  struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> >> >                                           struct device *dev)
> >> > @@ -319,9 +318,8 @@ EXPORT_SYMBOL_GPL(dma_buf_detach);
> >> >   * @attach:    [in]    attachment whose scatterlist is to be returned
> >> >   * @direction: [in]    direction of DMA transfer
> >> >   *
> >> > - * Returns sg_table containing the scatterlist to be returned; may return NULL
> >> > - * or ERR_PTR.
> >> > - *
> >> > + * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
> >> > + * on error.
> >> >   */
> >> >  struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                                         enum dma_data_direction direction)
> >> > @@ -334,6 +332,8 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> >> >                 return ERR_PTR(-EINVAL);
> >> >
> >> >         sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> >> > +       if (!sg_table)
> >> > +               sg_table = ERR_PTR(-ENOMEM);
> >> >
> >> >         return sg_table;
> >> >  }
> >> > @@ -544,6 +544,8 @@ EXPORT_SYMBOL_GPL(dma_buf_mmap);
> >> >   * These calls are optional in drivers. The intended use for them
> >> >   * is for mapping objects linear in kernel space for high use objects.
> >> >   * Please attempt to use kmap/kunmap before thinking about these interfaces.
> >> > + *
> >> > + * Returns NULL on error.
> >> >   */
> >> >  void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >  {
> >> > @@ -566,7 +568,9 @@ void *dma_buf_vmap(struct dma_buf *dmabuf)
> >> >         BUG_ON(dmabuf->vmap_ptr);
> >> >
> >> >         ptr = dmabuf->ops->vmap(dmabuf);
> >> > -       if (IS_ERR_OR_NULL(ptr))
> >> > +       if (WARN_ON_ONCE(IS_ERR(ptr)))
> >>
> >> since vmap is optional, the WARN_ON might be a bit strong..  although
> >> it would be a bit strange for an exporter to supply a vmap fxn which
> >> always returned NULL, not sure about that.  Just thought I'd mention
> >> it in case anyone else had an opinion about that.
> >
> > Yeah, I don't like this, it could cause unnecessary reports of problems.
> 
> The WARN_ON_ONCE is only if the vmap op returns ERR_PTR, not if it
> returns NULL.  This is designed to catch vmap ops that don't follow
> the spec, so I would call them necessary reports, but I can take it
> out if you still disagree.

Ah, ok, that makes more sense.  I'll queue this up.

thanks,

greg k-h