Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751980AbaBGQmJ (ORCPT ); Fri, 7 Feb 2014 11:42:09 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:57484 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751433AbaBGQmD (ORCPT ); Fri, 7 Feb 2014 11:42:03 -0500 Date: Fri, 7 Feb 2014 08:43:13 -0800 From: Greg Kroah-Hartman To: Rob Clark Cc: Colin Cross , Linux Kernel Mailing List , Sumit Semwal , David Airlie , Inki Dae , Joonyoung Shim , Seung-Woo Kim , Kyungmin Park , Kukjin Kim , Pawel Osciak , Marek Szyprowski , Mauro Carvalho Chehab , "open list:DMA BUFFER SHARIN..." , "open list:DMA BUFFER SHARIN..." , "open list:DMA BUFFER SHARIN..." , "moderated list:ARM/S5P EXYNOS AR..." , "moderated list:ARM/S5P EXYNOS AR..." Subject: Re: [PATCH] dma-buf: avoid using IS_ERR_OR_NULL Message-ID: <20140207164313.GA32655@kroah.com> References: <1387586630-1954-1-git-send-email-ccross@android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 21, 2013 at 07:42:17AM -0500, Rob Clark wrote: > On Fri, Dec 20, 2013 at 7:43 PM, Colin Cross 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 > > --- > > 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 -- 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/