[PATCH 0/3] dma, nvme, powerpc: introduce and implement DMA_ATTR_NO_WARN

@@ -126,3 +126,20 @@ means that we won't try quite as hard to get them.
 
 NOTE: At the moment DMA_ATTR_ALLOC_SINGLE_PAGES is only implemented on ARM,
 though ARM64 patches will likely be posted soon.
+
+DMA_ATTR_NO_WARN
+----------------
+
+This tells the DMA-mapping subsystem to supress allocation failure reports
+(similarly to __GFP_NOWARN).
+
+On some architectures allocation failures are reported with error messages
+to the system logs.  Although this can help to identify and debug problems,
+drivers which handle failures (eg, retry later) have no problems with them,
+and can actually flood the system logs with error messages that aren't any
+problem at all, depending on the implementation of the retry mechanism.
+
+So, this provides a way for drivers to avoid those error messages on calls
+where allocation failures are not a problem, and shouldn't bother the logs.
+
+NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC.

@@ -19,6 +19,7 @@ enum dma_attr {
 	DMA_ATTR_SKIP_CPU_SYNC,
 	DMA_ATTR_FORCE_CONTIGUOUS,
 	DMA_ATTR_ALLOC_SINGLE_PAGES,
+	DMA_ATTR_NO_WARN,
 	DMA_ATTR_MAX,
 };
 

@@ -18,6 +18,7 @@
 #include <linux/blk-mq.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/dma-attrs.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/genhd.h>

@@ -65,6 +66,8 @@ MODULE_PARM_DESC(use_cmb_sqes, "use controller's memory buffer for I/O SQes");
 
 static struct workqueue_struct *nvme_workq;
 
+static DEFINE_DMA_ATTRS(nvme_dma_attrs);
+
 struct nvme_dev;
 struct nvme_queue;
 

@@ -498,7 +501,7 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
 		goto out;
 
 	ret = BLK_MQ_RQ_QUEUE_BUSY;
-	if (!dma_map_sg(dev->dev, iod->sg, iod->nents, dma_dir))
+	if (!dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir, &nvme_dma_attrs))
 		goto out;
 
 	if (!nvme_setup_prps(dev, req, size))

@@ -516,7 +519,7 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
 		if (rq_data_dir(req))
 			nvme_dif_remap(req, nvme_dif_prep);
 
-		if (!dma_map_sg(dev->dev, &iod->meta_sg, 1, dma_dir))
+		if (!dma_map_sg_attrs(dev->dev, &iod->meta_sg, 1, dma_dir, &nvme_dma_attrs))
 			goto out_unmap;
 	}
 

@@ -2118,6 +2121,9 @@ static int __init nvme_init(void)
 	result = pci_register_driver(&nvme_driver);
 	if (result)
 		destroy_workqueue(nvme_workq);
+
+	dma_set_attr(DMA_ATTR_NO_WARN, &nvme_dma_attrs);
+
 	return result;
 }
 

@@ -479,7 +479,7 @@ int ppc_iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 
 		/* Handle failure */
 		if (unlikely(entry == DMA_ERROR_CODE)) {
-			if (printk_ratelimit())
+			if (unlikely(!dma_get_attr(DMA_ATTR_NO_WARN, attrs)) && printk_ratelimit())
 				dev_info(dev, "iommu_alloc failed, tbl %p "
 					 "vaddr %lx npages %lu\n", tbl, vaddr,
 					 npages);

@@ -776,7 +776,7 @@ dma_addr_t iommu_map_page(struct device *dev, struct iommu_table *tbl,
 					 mask >> tbl->it_page_shift, align,
 					 attrs);
 		if (dma_handle == DMA_ERROR_CODE) {
-			if (printk_ratelimit())  {
+			if (unlikely(!dma_get_attr(DMA_ATTR_NO_WARN, attrs)) && printk_ratelimit())  {
 				dev_info(dev, "iommu_alloc failed, tbl %p "
 					 "vaddr %p npages %d\n", tbl, vaddr,
 					 npages);