linux-kernel - [PATCH] udmabuf: change folios array from kmalloc to kvmalloc

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Message-ID: <20240717065444.369876-1-link@vivo.com>
Date: Wed, 17 Jul 2024 14:54:43 +0800
From: Huan Yang <link@...o.com>
To: Gerd Hoffmann <kraxel@...hat.com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	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,
	Huan Yang <link@...o.com>
Subject: [PATCH] udmabuf: change folios array from kmalloc to kvmalloc

When PAGE_SIZE 4096, MAX_PAGE_ORDER 10, 64bit machine,
change size limit into 3GB and then create a udmabuf,
current ubuf->folios alloc from kmalloc_array will trigger this
warn and 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, so can save 524288 pages(2GB).

So, 2GB above size can not support in current udmabuf.

Further more, costly order(order 3) may not be guaranteed that it can be
applied for, due to fragmentation.

This patch change folios arrary 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>
---
 drivers/dma-buf/udmabuf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 047c3cd2ceff..71182a6d35b1 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -197,7 +197,7 @@ static void release_udmabuf(struct dma_buf *buf)
 
 	unpin_all_folios(&ubuf->unpin_list);
 	kfree(ubuf->offsets);
-	kfree(ubuf->folios);
+	kvfree(ubuf->folios);
 	kfree(ubuf);
 }
 
@@ -322,7 +322,7 @@ static long udmabuf_create(struct miscdevice *device,
 	if (!ubuf->pagecount)
 		goto err;
 
-	ubuf->folios = kmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
+	ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
 				    GFP_KERNEL);
 	if (!ubuf->folios) {
 		ret = -ENOMEM;
@@ -399,7 +399,7 @@ static long udmabuf_create(struct miscdevice *device,
 		fput(memfd);
 	unpin_all_folios(&ubuf->unpin_list);
 	kfree(ubuf->offsets);
-	kfree(ubuf->folios);
+	kvfree(ubuf->folios);
 	kfree(ubuf);
 	return ret;
 }

base-commit: 523b23f0bee3014a7a752c9bb9f5c54f0eddae88
-- 
2.45.2