[PATCH] swiotlb: check alloc_size before the allocation of a new memory pool

[Peng Zhang]

From: ZhangPeng <zhangpeng362@xxxxxxxxxx>

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

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 33d942615be5..cc92cff02c60 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1126,6 +1126,9 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
 	u64 phys_limit;
 	int index;
 
+	if (alloc_size > IO_TLB_SEGSIZE * IO_TLB_SIZE)
+		return -1;
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(pool, &mem->pools, node) {
 		index = swiotlb_pool_find_slots(dev, pool, orig_addr,
-- 
2.25.1