swiotlb: checking whether swiotlb buffer is full with io_tlb_used

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@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index bedc9f945836..a01b83e95a2a 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;