linux-kernel - Re: [PATCH 2/5] udmabuf: change folios array from kmalloc to kvmalloc

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Message-ID: <e838be76-e0c0-4e87-b77d-a968318e704d@amd.com>
Date: Thu, 1 Aug 2024 12:54:20 +0200
From: Christian König <christian.koenig@....com>
To: Huan Yang <link@...o.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Sumit Semwal <sumit.semwal@...aro.org>, dri-devel@...ts.freedesktop.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
 linux-kernel@...r.kernel.org
Cc: opensource.kernel@...o.com
Subject: Re: [PATCH 2/5] udmabuf: change folios array from kmalloc to kvmalloc

Am 01.08.24 um 12:45 schrieb Huan Yang:
> When PAGE_SIZE 4096, MAX_PAGE_ORDER 10, 64bit machine,
> page_alloc only support 4MB.
> If above this, trigger this warn and return NULL.
>
> udmabuf can change size limit, if change it to 3072(3GB), and then alloc
> 3GB udmabuf, will fail create.
>
> [ 4080.876581] ------------[ cut here ]------------
> [ 4080.876843] WARNING: CPU: 3 PID: 2015 at mm/page_alloc.c:4556 __alloc_pages+0x2c8/0x350
> [ 4080.878839] RIP: 0010:__alloc_pages+0x2c8/0x350
> [ 4080.879470] Call Trace:
> [ 4080.879473]  <TASK>
> [ 4080.879473]  ? __alloc_pages+0x2c8/0x350
> [ 4080.879475]  ? __warn.cold+0x8e/0xe8
> [ 4080.880647]  ? __alloc_pages+0x2c8/0x350
> [ 4080.880909]  ? report_bug+0xff/0x140
> [ 4080.881175]  ? handle_bug+0x3c/0x80
> [ 4080.881556]  ? exc_invalid_op+0x17/0x70
> [ 4080.881559]  ? asm_exc_invalid_op+0x1a/0x20
> [ 4080.882077]  ? udmabuf_create+0x131/0x400
>
> Because MAX_PAGE_ORDER, kmalloc can max alloc 4096 * (1 << 10), 4MB
> memory, each array entry is pointer(8byte), so can save 524288 pages(2GB).
>
> Further more, costly order(order 3) may not be guaranteed that it can be
> applied for, due to fragmentation.
>
> This patch change udmabuf array use kvmalloc_array, this can fallback
> alloc into vmalloc, which can guarantee allocation for any size and does
> not affect the performance of kmalloc allocations.
>
> Signed-off-by: Huan Yang <link@...o.com>

Acked-by: Christian König <christian.koenig@....com>

> ---
>   drivers/dma-buf/udmabuf.c | 26 +++++++++++++-------------
>   1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index d69aeada7367..a915714c5dce 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -83,7 +83,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
>   
>   	dma_resv_assert_held(buf->resv);
>   
> -	pages = kmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);
> +	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);
>   	if (!pages)
>   		return -ENOMEM;
>   
> @@ -91,7 +91,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
>   		pages[pg] = &ubuf->folios[pg]->page;
>   
>   	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
> -	kfree(pages);
> +	kvfree(pages);
>   	if (!vaddr)
>   		return -EINVAL;
>   
> @@ -203,8 +203,8 @@ static void release_udmabuf(struct dma_buf *buf)
>   		put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
>   
>   	unpin_all_folios(&ubuf->unpin_list);
> -	kfree(ubuf->offsets);
> -	kfree(ubuf->folios);
> +	kvfree(ubuf->offsets);
> +	kvfree(ubuf->folios);
>   	kfree(ubuf);
>   }
>   
> @@ -330,14 +330,14 @@ static long udmabuf_create(struct miscdevice *device,
>   	if (!ubuf->pagecount)
>   		goto err;
>   
> -	ubuf->folios = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
> -				    GFP_KERNEL);
> +	ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
> +				      GFP_KERNEL);
>   	if (!ubuf->folios) {
>   		ret = -ENOMEM;
>   		goto err;
>   	}
> -	ubuf->offsets = kcalloc(ubuf->pagecount, sizeof(*ubuf->offsets),
> -				GFP_KERNEL);
> +	ubuf->offsets =
> +		kvcalloc(ubuf->pagecount, sizeof(*ubuf->offsets), GFP_KERNEL);
>   	if (!ubuf->offsets) {
>   		ret = -ENOMEM;
>   		goto err;
> @@ -351,7 +351,7 @@ static long udmabuf_create(struct miscdevice *device,
>   			goto err;
>   
>   		pgcnt = list[i].size >> PAGE_SHIFT;
> -		folios = kmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
> +		folios = kvmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
>   		if (!folios) {
>   			ret = -ENOMEM;
>   			goto err;
> @@ -361,7 +361,7 @@ static long udmabuf_create(struct miscdevice *device,
>   		ret = memfd_pin_folios(memfd, list[i].offset, end,
>   				       folios, pgcnt, &pgoff);
>   		if (ret <= 0) {
> -			kfree(folios);
> +			kvfree(folios);
>   			if (!ret)
>   				ret = -EINVAL;
>   			goto err;
> @@ -390,7 +390,7 @@ static long udmabuf_create(struct miscdevice *device,
>   			}
>   		}
>   
> -		kfree(folios);
> +		kvfree(folios);
>   		fput(memfd);
>   		memfd = NULL;
>   	}
> @@ -406,8 +406,8 @@ static long udmabuf_create(struct miscdevice *device,
>   	if (memfd)
>   		fput(memfd);
>   	unpin_all_folios(&ubuf->unpin_list);
> -	kfree(ubuf->offsets);
> -	kfree(ubuf->folios);
> +	kvfree(ubuf->offsets);
> +	kvfree(ubuf->folios);
>   	kfree(ubuf);
>   	return ret;
>   }