linux-kernel - Re: [PATCH] lib/dma-debug.c: fix __hash_bucket

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Date:	Thu, 18 Oct 2012 23:53:41 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ming Lei <ming.lei@...onical.com>,
	Joerg Roedel <joerg.roedel@....com>,
	Shuah Khan <shuah.khan@...com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jakub Kicinski <kubakici@...pl>
Subject: Re: [PATCH] lib/dma-debug.c: fix __hash_bucket_find

Hi,

Below v1 should be more efficient and simper, sorry for the noise.


Thanks,
--
Ming Lei

--
>From d275d195794ff80e018145f2fae714b35ddc49e2 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@...onical.com>
Date: Thu, 18 Oct 2012 23:30:57 +0800
Subject: [PATCH v1] lib/dma-debug.c: fix __hash_bucket_find

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@....com>
Cc: Shuah Khan <shuah.khan@...com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jakub Kicinski <kubakici@...pl>
Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 lib/dma-debug.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index 94aa94e..59f4a1a 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -277,7 +277,7 @@ static struct dma_debug_entry
*__hash_bucket_find(struct hash_bucket *bucket,
 						  match_fn match)
 {
 	struct dma_debug_entry *entry, *ret = NULL;
-	int matches = 0, match_lvl, last_lvl = 0;
+	int matches = 0, match_lvl, last_lvl = -1;

 	list_for_each_entry(entry, &bucket->list, list) {
 		if (!match(ref, entry))
@@ -306,7 +306,7 @@ static struct dma_debug_entry
*__hash_bucket_find(struct hash_bucket *bucket,
 		} else if (match_lvl > last_lvl) {
 			/*
 			 * We found an entry that fits better then the
-			 * previous one
+			 * previous one or it is the 1st match.
 			 */
 			last_lvl = match_lvl;
 			ret      = entry;
-- 
1.7.9.5
--
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