dma-debug: fix locking bug in check_unmap()

In check_unmap() it is possible to get into a dead-locked state if
dma_mapping_error is called. The problem is that the bucket is locked in
check_unmap, and locked again by debug_dma_mapping_error which is called
by dma_mapping_error. To resolve that we must release the lock on the
bucket before making the call to dma_mapping_error.

[[e-mail]: restore 80-col trickery to be consistent with the rest of the file]
Signed-off-by: Alexander Duyck <[e-mail]>
Cc: Joerg Roedel <[e-mail]>
Reviewed-by: Shuah Khan <[e-mail]>
Tested-by: Shuah Khan <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Cc: Konrad Rzeszutek Wilk <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/dma-debug.c

···
 	entry = bucket_find_exact(bucket, ref);
 
 	if (!entry) {
+		/* must drop lock before calling dma_mapping_error */
+		put_hash_bucket(bucket, &flags);
+
 		if (dma_mapping_error(ref->dev, ref->dev_addr)) {
 			err_printk(ref->dev, NULL,
-				   "DMA-API: device driver tries "
-				   "to free an invalid DMA memory address\n");
-			return;
+				   "DMA-API: device driver tries to free an "
+				   "invalid DMA memory address\n");
+		} else {
+			err_printk(ref->dev, NULL,
+				   "DMA-API: device driver tries to free DMA "
+				   "memory it has not allocated [device "
+				   "address=0x%016llx] [size=%llu bytes]\n",
+				   ref->dev_addr, ref->size);
 		}
-		err_printk(ref->dev, NULL, "DMA-API: device driver tries "
-			   "to free DMA memory it has not allocated "
-			   "[device address=0x%016llx] [size=%llu bytes]\n",
-			   ref->dev_addr, ref->size);
-		goto out;
+		return;
 	}
 
 	if (ref->size != entry->size) {
···
 	hash_bucket_del(entry);
 	dma_entry_free(entry);
 
-out:
 	put_hash_bucket(bucket, &flags);
 }