From: Leon Romanovsky <leon@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Alexandra Winter <wintera@linux.ibm.com>,
Wenjia Zhang <wenjia@linux.ibm.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
Russell King <linux@armlinux.org.uk>,
Robin Murphy <robin.murphy@arm.com>,
linux-arm-kernel@lists.infradead.org, linux-rdma@vger.kernel.org,
iommu@lists.linux.dev, linux-media@vger.kernel.org,
netdev@vger.kernel.org, linux-s390@vger.kernel.org,
alsa-devel@alsa-project.org
Subject: Re: [PATCH 7/7] dma-mapping: reject __GFP_COMP in dma_alloc_attrs
Date: Mon, 14 Nov 2022 10:11:50 +0200 [thread overview]
Message-ID: <Y3H4RobK/pmDd3xG@unreal> (raw)
In-Reply-To: <20221113163535.884299-8-hch@lst.de>
On Sun, Nov 13, 2022 at 05:35:35PM +0100, Christoph Hellwig wrote:
> DMA allocations can never be turned back into a page pointer, so
> requesting compound pages doesn't make sense and it can't even be
> supported at all by various backends.
>
> Reject __GFP_COMP with a warning in dma_alloc_attrs, and stop clearing
> the flag in the arm dma ops and dma-iommu.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/arm/mm/dma-mapping.c | 17 -----------------
> drivers/iommu/dma-iommu.c | 3 ---
> kernel/dma/mapping.c | 8 ++++++++
> 3 files changed, 8 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index d7909091cf977..c135f6e37a00c 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -564,14 +564,6 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> if (mask < 0xffffffffULL)
> gfp |= GFP_DMA;
>
> - /*
> - * Following is a work-around (a.k.a. hack) to prevent pages
> - * with __GFP_COMP being passed to split_page() which cannot
> - * handle them. The real problem is that this flag probably
> - * should be 0 on ARM as it is not supported on this
> - * platform; see CONFIG_HUGETLBFS.
> - */
> - gfp &= ~(__GFP_COMP);
> args.gfp = gfp;
>
> *handle = DMA_MAPPING_ERROR;
> @@ -1093,15 +1085,6 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
> return __iommu_alloc_simple(dev, size, gfp, handle,
> coherent_flag, attrs);
>
> - /*
> - * Following is a work-around (a.k.a. hack) to prevent pages
> - * with __GFP_COMP being passed to split_page() which cannot
> - * handle them. The real problem is that this flag probably
> - * should be 0 on ARM as it is not supported on this
> - * platform; see CONFIG_HUGETLBFS.
> - */
> - gfp &= ~(__GFP_COMP);
> -
> pages = __iommu_alloc_buffer(dev, size, gfp, attrs, coherent_flag);
> if (!pages)
> return NULL;
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 9297b741f5e80..f798c44e09033 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -744,9 +744,6 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
> /* IOMMU can map any pages, so himem can also be used here */
> gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
>
> - /* It makes no sense to muck about with huge pages */
> - gfp &= ~__GFP_COMP;
> -
> while (count) {
> struct page *page = NULL;
> unsigned int order_size;
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 33437d6206445..c026a5a5e0466 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -498,6 +498,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
>
> WARN_ON_ONCE(!dev->coherent_dma_mask);
>
> + /*
> + * DMA allocations can never be turned back into a page pointer, so
> + * requesting compound pages doesn't make sense (and can't even be
> + * supported at all by various backends).
> + */
> + if (WARN_ON_ONCE(flag & __GFP_COMP))
> + return NULL;
In RDMA patches, you wrote that GFP_USER is not legal flag either. So it
is better to WARN here for everything that is not allowed.
> +
> if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))
> return cpu_addr;
>
> --
> 2.30.2
>
next prev parent reply other threads:[~2022-11-14 8:11 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-13 16:35 stop drivers from passing GFP_COMP to dma_alloc_coherent Christoph Hellwig
2022-11-13 16:35 ` [PATCH 1/7] media: videobuf-dma-contig: use dma_mmap_coherent Christoph Hellwig
2022-11-24 14:10 ` Hans Verkuil
2022-11-29 14:00 ` Christoph Hellwig
2022-11-13 16:35 ` [PATCH 2/7] RDMA/hfi1: don't pass bogus GFP_ flags to dma_alloc_coherent Christoph Hellwig
2022-11-15 20:39 ` Jason Gunthorpe
2022-11-16 14:40 ` Dean Luick
2022-11-16 15:15 ` Robin Murphy
2022-11-16 15:45 ` Christoph Hellwig
2022-11-16 17:49 ` Dean Luick
2022-11-20 20:41 ` Dean Luick
2022-11-16 16:21 ` Dean Luick
2022-11-16 18:37 ` Robin Murphy
2022-11-13 16:35 ` [PATCH 3/7] RDMA/qib: " Christoph Hellwig
2022-11-15 20:40 ` Jason Gunthorpe
2022-11-13 16:35 ` [PATCH 4/7] cnic: " Christoph Hellwig
2022-11-13 16:35 ` [PATCH 5/7] s390/ism: " Christoph Hellwig
2022-11-16 12:39 ` Wenjia Zhang
2022-11-13 16:35 ` [PATCH 6/7] ALSA: memalloc: don't pass bogus GFP_ flags to dma_alloc_* Christoph Hellwig
2022-11-14 9:04 ` Takashi Iwai
2022-11-21 8:37 ` Christoph Hellwig
2022-11-13 16:35 ` [PATCH 7/7] dma-mapping: reject __GFP_COMP in dma_alloc_attrs Christoph Hellwig
2022-11-14 8:11 ` Leon Romanovsky [this message]
2022-11-16 6:11 ` Christoph Hellwig
2022-11-16 7:11 ` Leon Romanovsky
2022-11-14 12:16 ` Marek Szyprowski
2022-11-21 8:39 ` stop drivers from passing GFP_COMP to dma_alloc_coherent Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y3H4RobK/pmDd3xG@unreal \
--to=leon@kernel.org \
--cc=alsa-devel@alsa-project.org \
--cc=dennis.dalessandro@cornelisnetworks.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux.dev \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=m.szyprowski@samsung.com \
--cc=mchehab@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=perex@perex.cz \
--cc=robin.murphy@arm.com \
--cc=tiwai@suse.com \
--cc=wenjia@linux.ibm.com \
--cc=wintera@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).