[PATCH] lib/dma-debug.c: fix __hash_bucket_find

[Ming Lei <ming.lei@canonical.com>]

If there is only one match, the unique matched entry should be returned.

Without the fix, the commit f62566214fe31c9f9b3218a42f1b19e6a9e6844a

	dma-debug: new interfaces to debug dma mapping errors

can't work reliably because only device and dma_addr are passed to
dma_mapping_error().

Cc: Joerg Roedel <joerg.roedel@amd.com>
Cc: Shuah Khan <shuah.khan@hp.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 lib/dma-debug.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 94aa94e..be132f3 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -283,6 +283,10 @@ static struct dma_debug_entry *__hash_bucket_find(struct hash_bucket *bucket,
 		if (!match(ref, entry))
 			continue;
 
+		/* record the first match */
+		if (!ret)
+			ret = entry;
+
 		/*
 		 * Some drivers map the same physical address multiple
 		 * times. Without a hardware IOMMU this results in the
-- 
1.7.9.5