linux-kernel - RE: [EXT] Re: [PATCH] Supports to use the default CMA when the device-specified CMA memory is not enough.

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Message-ID:
 <AS1PR04MB955995BF689849177D95DE28EAC02@AS1PR04MB9559.eurprd04.prod.outlook.com>
Date: Wed, 12 Jun 2024 07:34:56 +0000
From: Zhai He <zhai.he@....com>
To: Greg KH <gregkh@...uxfoundation.org>
CC: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"sboyd@...nel.org" <sboyd@...nel.org>, "linux-mm@...ck.org"
	<linux-mm@...ck.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "stable@...r.kernel.org"
	<stable@...r.kernel.org>, Zhipeng Wang <zhipeng.wang_1@....com>, Jindong Yue
	<jindong.yue@....com>
Subject: RE: [EXT] Re: [PATCH] Supports to use the default CMA when the
 device-specified CMA memory is not enough.

Thanks Greg for your review.
The reason I changed the error level is because these logs will be printed
when memory allocation from the specified device CMA fails, but if the
allocation fails, it will be allocated from the default cma area. It can
easily mislead developers' judgment, so I changed it to debug level.
I will not use "__func__" in the next version of this patch.

-----Original Message-----
From: Greg KH <gregkh@...uxfoundation.org> 
Sent: Wednesday, June 12, 2024 3:20 PM
To: Zhai He <zhai.he@....com>
Cc: akpm@...ux-foundation.org; sboyd@...nel.org; linux-mm@...ck.org;
linux-kernel@...r.kernel.org; stable@...r.kernel.org; Zhipeng Wang
<zhipeng.wang_1@....com>; Jindong Yue <jindong.yue@....com>
Subject: [EXT] Re: [PATCH] Supports to use the default CMA when the
device-specified CMA memory is not enough.

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On Wed, Jun 12, 2024 at 10:38:31AM +0800, zhai.he wrote:
> From: He Zhai <zhai.he@....com>
>
> In the current code logic, if the device-specified CMA memory 
> allocation fails, memory will not be allocated from the default CMA area.
> This patch will use the default cma region when the device's specified 
> CMA is not enough.
>
> Signed-off-by: He Zhai <zhai.he@....com>
> ---
>  kernel/dma/contiguous.c | 11 +++++++++--
>  mm/cma.c                |  2 +-
>  2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 
> 055da410ac71..e45cfb24500f 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -357,8 +357,13 @@ struct page *dma_alloc_contiguous(struct device *dev,
size_t size, gfp_t gfp)
>       /* CMA can be used only in the context which permits sleeping */
>       if (!gfpflags_allow_blocking(gfp))
>               return NULL;
> -     if (dev->cma_area)
> -             return cma_alloc_aligned(dev->cma_area, size, gfp);
> +     if (dev->cma_area) {
> +             struct page *page = NULL;
> +
> +             page = cma_alloc_aligned(dev->cma_area, size, gfp);
> +             if (page)
> +                     return page;
> +     }
>       if (size <= PAGE_SIZE)
>               return NULL;
>
> @@ -406,6 +411,8 @@ void dma_free_contiguous(struct device *dev, struct
page *page, size_t size)
>       if (dev->cma_area) {
>               if (cma_release(dev->cma_area, page, count))
>                       return;
> +             if (cma_release(dma_contiguous_default_area, page, count))
> +                     return;
>       } else {
>               /*
>                * otherwise, page is from either per-numa cma or 
> default cma diff --git a/mm/cma.c b/mm/cma.c index 
> 3e9724716bad..f225b3f65bd2 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -495,7 +495,7 @@ struct page *cma_alloc(struct cma *cma, unsigned long
count,
>       }
>
>       if (ret && !no_warn) {
> -             pr_err_ratelimited("%s: %s: alloc failed, req-size: %lu
pages, ret: %d\n",
> +             pr_debug("%s: %s: alloc failed, req-size: %lu pages, 
> + ret: %d, try to use default cma\n",
>                                  __func__, cma->name, count, ret);

Why did you change the error level here?

And when you use pr_debug(), you NEVER need to use __func__, as it is
already included automatically in the message output.  So now you have it
twice :)

thanks,

greg k-h

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