linux-ext4 - Re: [PATCH] debugfs: Fix infinite loop when dump log

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Date: Mon, 27 Nov 2023 14:54:05 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>,
	<linux-ext4@...r.kernel.org>
CC: <louhongxiang@...wei.com>
Subject: Re: [PATCH] debugfs: Fix infinite loop when dump log

On 2023/11/17 18:23, Wenchao Hao wrote:
> There are 2 scenarios which would trigger infinite loop:
> 
> 1. None log is recorded, then dumplog with "-n", for example:
>     debugfs -R "logdump -O -n 10" /dev/xxx
>     while /dev/xxx has no valid log recorded.
> 2. The log area is full and cycle write is triggered, then dumplog with
>     debugfs -R "logdump -aOS" /dev/xxx
> 
> This patch add a new flag "reverse_flag" to mark if logdump has reached
> to tail of logarea, it is default false, and set in macro WRAP().
> 
> If reverse_flag is true, and we comes to first_transaction_blocknr
> again, just break the logdump loop.

Friendly ping...

> 
> Signed-off-by: Wenchao Hao <haowenchao2@...wei.com>
> ---
>   debugfs/logdump.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/debugfs/logdump.c b/debugfs/logdump.c
> index b600228e..05ea839a 100644
> --- a/debugfs/logdump.c
> +++ b/debugfs/logdump.c
> @@ -52,6 +52,7 @@ static int64_t		dump_counts;
>   static blk64_t		block_to_dump, bitmap_to_dump, inode_block_to_dump;
>   static unsigned int	group_to_dump, inode_offset_to_dump;
>   static ext2_ino_t	inode_to_dump;
> +static bool		reverse_flag;
>   
>   struct journal_source
>   {
> @@ -80,8 +81,10 @@ static void dump_fc_block(FILE *out_file, char *buf, int blocksize,
>   static void do_hexdump (FILE *, char *, int);
>   
>   #define WRAP(jsb, blocknr, maxlen)					\
> -	if (blocknr >= (maxlen))					\
> -	    blocknr -= (maxlen - be32_to_cpu((jsb)->s_first));
> +	if (blocknr >= (maxlen)) {					\
> +		blocknr -= (maxlen - be32_to_cpu((jsb)->s_first));	\
> +		reverse_flag = true;					\
> +	}
>   
>   void do_logdump(int argc, char **argv, int sci_idx EXT2FS_ATTR((unused)),
>   		    void *infop EXT2FS_ATTR((unused)))
> @@ -115,6 +118,7 @@ void do_logdump(int argc, char **argv, int sci_idx EXT2FS_ATTR((unused)),
>   	inode_block_to_dump = ANY_BLOCK;
>   	inode_to_dump = -1;
>   	dump_counts = -1;
> +	reverse_flag = false;
>   
>   	reset_getopt();
>   	while ((c = getopt (argc, argv, "ab:ci:f:OsSn:")) != EOF) {
> @@ -477,8 +481,7 @@ static void dump_journal(char *cmdname, FILE *out_file,
>   		if (dump_old && (dump_counts != -1) && (cur_counts >= dump_counts))
>   			break;
>   
> -		if ((blocknr == first_transaction_blocknr) &&
> -		    (cur_counts != 0) && dump_old && (dump_counts != -1)) {
> +		if ((blocknr == first_transaction_blocknr) && dump_old && reverse_flag) {
>   			fprintf(out_file, "Dump all %lld journal records.\n",
>   				(long long) cur_counts);
>   			break;