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From:   Miles Chen <miles.chen@mediatek.com>
To:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>
CC:     <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        <linux-mediatek@lists.infradead.org>, <wsd_upstream@mediatek.com>,
        Miles Chen <miles.chen@mediatek.com>
Subject: [PATCH] mm: slub: print_hex_dump() with DUMP_PREFIX_OFFSET
Date:   Fri, 20 Sep 2019 18:48:49 +0800
Message-ID: <20190920104849.32504-1-miles.chen@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Since commit ad67b74d2469d9b8 ("printk: hash addresses printed with %p"),
The use DUMP_PREFIX_OFFSET instead of DUMP_PREFIX_ADDRESS with
print_hex_dump() can generate more useful messages.

In the following example, it's easier get the offset of incorrect poison
value with DUMP_PREFIX_OFFSET.

Before:
Object 00000000e817b73b: 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000000816f4601: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000000169d2bb8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000000f4c38716: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000000917e3491: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000000c0e33738: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 000000001755ddd1: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b

After:
Object 00000000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000010: 63 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000020: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b
Object 00000030: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5

I think it might be worth to convert all DUMP_PREFIX_ADDRESS to
DUMP_PREFIX_OFFSET for the whole Linux kernel.

$ git grep 'DUMP_PREFIX_ADDRESS' | cut -f1 -d"/" | sort | uniq -c
3 arch
140 drivers
12 fs
1 include
5 lib
2 mm

Signed-off-by: Miles Chen <miles.chen@mediatek.com>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 8834563cdb4b..89d91c1eb33d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -528,7 +528,7 @@ static void print_section(char *level, char *text, u8 *addr,
 			  unsigned int length)
 {
 	metadata_access_enable();
-	print_hex_dump(level, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
+	print_hex_dump(level, text, DUMP_PREFIX_OFFSET, 16, 1, addr,
 			length, 1);
 	metadata_access_disable();
 }
-- 
2.18.0