linux-kernel - Re: [PATCH 2/2] jffs2: fix buffer dump debug output

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Date:	Tue, 21 Oct 2014 11:47:34 +0200
From:	Cyrille Pitchen <cyrille.pitchen@...el.com>
To:	Joe Perches <joe@...ches.com>
CC:	<dwmw2@...radead.org>, <linux-mtd@...ts.infradead.org>,
	<nicolas.ferre@...el.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] jffs2: fix buffer dump debug output

Le 21/10/2014 10:17, Joe Perches a écrit :
> On Tue, 2014-10-21 at 10:05 +0200, Cyrille Pitchen wrote:
>> This patch fixes __jffs2_dbg_dump_buffer(): this function prints a message
>> claiming to dump len bytes. However, depending on the start offset, the former
>> code drops up to 31 (JFFS2_BUFDUMP_BYTES_PER_LINE - 1) bytes.
>>
>> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@...el.com>
>> ---
>>  fs/jffs2/debug.c | 21 ++++++++-------------
>>  1 file changed, 8 insertions(+), 13 deletions(-)
>>
>> diff --git a/fs/jffs2/debug.c b/fs/jffs2/debug.c
>> index 07bd5bc..1b515b2 100644
>> --- a/fs/jffs2/debug.c
>> +++ b/fs/jffs2/debug.c
>> @@ -736,30 +736,25 @@ void
>>  __jffs2_dbg_dump_buffer(unsigned char *buf, int len, uint32_t offs)
>>  {
>>  	int skip;
>> -	int i;
>> +	int i, pos;
>>  
>>  	printk(JFFS2_DBG_MSG_PREFIX " dump from offset %#08x to offset %#08x (%x bytes).\n",
>>  		offs, offs + len, len);
>> -	i = skip = offs % JFFS2_BUFDUMP_BYTES_PER_LINE;
>> +	i = skip = offs & (JFFS2_BUFDUMP_BYTES_PER_LINE - 1);
>>  	offs = offs & ~(JFFS2_BUFDUMP_BYTES_PER_LINE - 1);
>>  
>> -	if (skip != 0)
>> -		printk(JFFS2_DBG "%#08x: ", offs);
>> -
>> +	printk(JFFS2_DBG "%#08x: ", offs);
>>  	while (skip--)
>>  		printk("   ");
>>  
>> -	while (i < len) {
>> -		if ((i % JFFS2_BUFDUMP_BYTES_PER_LINE) == 0 && i != len -1) {
>> -			if (i != 0)
>> -				printk("\n");
>> +	for (pos = 0; pos < len; ++pos, ++i) {
>> +		if (i == JFFS2_BUFDUMP_BYTES_PER_LINE) {
>>  			offs += JFFS2_BUFDUMP_BYTES_PER_LINE;
>> -			printk(JFFS2_DBG "%0#8x: ", offs);
>> +			printk(JFFS2_DBG "\n%0#8x: ", offs);
>> +			i = 0;
> 
> print_hex_dump would be better
> 
> 
Hi Joe,

thanks for your comment. Indeed using print_hex_dump() would be a good idea
since it would avoid each driver to implement its own version of buffer dumps.
Reading the source code of print_hex_dump(), the output format would change a
little bit:
the output would no longer be aligned to JFFS2_BUFDUMP_BYTES_PER_LINE boundary
using leading spaces.
If it's ok to change the output format it's good for me as well.
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