Re: [PATCH 01/22] dma-debug: move initialization to common code

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Hi Christoph,

Nice cleanup! Looks good overall, just a couple of nits.

On 20/04/18 09:02, Christoph Hellwig wrote:
[...]
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 7f5cdc1e6b29..712a897174e4 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -41,6 +41,11 @@
  #define HASH_FN_SHIFT   13
  #define HASH_FN_MASK    (HASH_SIZE - 1)
+/* allow architectures to override this if absolutely required */
+#ifndef PREALLOC_DMA_DEBUG_ENTRIES
+#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)
+#endif
+
  enum {
  	dma_debug_single,
  	dma_debug_page,
@@ -1004,18 +1009,16 @@ void dma_debug_add_bus(struct bus_type *bus)
  	bus_register_notifier(bus, nb);
  }
-/*
- * Let the architectures decide how many entries should be preallocated.
- */
-void dma_debug_init(u32 num_entries)
+static int dma_debug_init(void)
  {
+	u32 num_entries;

Maybe initialise it to PREALLOC_DMA_DEBUG_ENTRIES?

  	int i;
/* Do not use dma_debug_initialized here, since we really want to be
  	 * called to set dma_debug_initialized
  	 */
  	if (global_disable)
-		return;
+		return 0;
for (i = 0; i < HASH_SIZE; ++i) {
  		INIT_LIST_HEAD(&dma_entry_hash[i].list);
@@ -1026,17 +1029,19 @@ void dma_debug_init(u32 num_entries)
  		pr_err("DMA-API: error creating debugfs entries - disabling\n");
  		global_disable = true;
- return;
+		return 0;
  	}
if (req_entries)
  		num_entries = req_entries;
+	else
+		num_entries = PREALLOC_DMA_DEBUG_ENTRIES;
if (prealloc_memory(num_entries) != 0) {
  		pr_err("DMA-API: debugging out of memory error - disabled\n");
  		global_disable = true;
- return;
+		return 0;
  	}
nr_total_entries = num_free_entries;
@@ -1044,7 +1049,9 @@ void dma_debug_init(u32 num_entries)
  	dma_debug_initialized = true;
pr_info("DMA-API: debugging enabled by kernel config\n");
+	return 0;
  }
+core_initcall(dma_debug_init);

I think it's worth noting that for most users this now happens much earlier than before. In general that's probably good (e.g. on arm64 it should prevent false-positives from the Arm SMMU drivers under ACPI), and I can't imagine it's high-risk, but it is a behaviour change.

Robin.

static __init int dma_debug_cmdline(char *str)
  {

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