[PATCH v3 3/3] swiotlb: checking whether swiotlb buffer is full with io_tlb_used

From: Dongli Zhang
Date: Fri Jan 18 2019 - 02:08:44 EST


This patch uses io_tlb_used to help check whether swiotlb buffer is full.
io_tlb_used is no longer used for only debugfs. It is also used to help
optimize swiotlb_tbl_map_single().

Suggested-by: Joe Jin <joe.jin@xxxxxxxxxx>
Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
---
Changed since v2:
* move #ifdef folding to previous patch (suggested by Konrad Rzeszutek Wilk)

kernel/dma/swiotlb.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index bedc9f9..a01b83e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -483,6 +483,10 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
* request and allocate a buffer from that IO TLB pool.
*/
spin_lock_irqsave(&io_tlb_lock, flags);
+
+ if (unlikely(nslots > io_tlb_nslabs - io_tlb_used))
+ goto not_found;
+
index = ALIGN(io_tlb_index, stride);
if (index >= io_tlb_nslabs)
index = 0;
--
2.7.4