linux-kernel - [PATCH v2] swiotlb: check alloc_size before the allocation of a new memory pool

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Date: Tue, 9 Jan 2024 10:45:47 +0800
From: Peng Zhang <zhangpeng362@...wei.com>
To: <hch@....de>, <m.szyprowski@...sung.com>, <robin.murphy@....com>,
	<petr.tesarik1@...wei-partners.com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
CC: <wangkefeng.wang@...wei.com>, <sunnanyong@...wei.com>,
	<zhangpeng362@...wei.com>
Subject: [PATCH v2] swiotlb: check alloc_size before the allocation of a new memory pool

From: ZhangPeng <zhangpeng362@...wei.com>

The allocation request for swiotlb contiguous memory greater than
128*2KB cannot be fulfilled because it exceeds the maximum contiguous
memory limit. If the swiotlb memory we allocate is larger than 128*2KB,
swiotlb_find_slots() will still schedule the allocation of a new memory
pool, which will increase memory overhead.

Fix it by adding a check with alloc_size no more than 128*2KB before
scheduling the allocation of a new memory pool in swiotlb_find_slots().

Signed-off-by: ZhangPeng <zhangpeng362@...wei.com>
Reviewed-by: Petr Tesarik <petr.tesarik1@...wei-partners.com>
---
v1->v2:
- Rebased on for-next branch per Christoph Hellwig
- Added RB from Petr Tesarik

 kernel/dma/swiotlb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 97c298b210bc..b079a9a8e087 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1136,6 +1136,9 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
 	int cpu, i;
 	int index;
 
+	if (alloc_size > IO_TLB_SEGSIZE * IO_TLB_SIZE)
+		return -1;
+
 	cpu = raw_smp_processor_id();
 	for (i = 0; i < default_nareas; ++i) {
 		index = swiotlb_search_area(dev, cpu, i, orig_addr, alloc_size,
-- 
2.25.1