linux-ext4 - Re: [PATCH] debugfs:fix repeated output problem with `logdump -O -n <num

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Date:   Sat, 26 Nov 2022 15:55:37 +0800
From:   "lihaoxiang (F)" <lihaoxiang9@...wei.com>
To:     <tytso@....edu>
CC:     <linux-ext4@...r.kernel.org>,
        Zhiqiang Liu <liuzhiqiang26@...wei.com>,
        <linfeilong@...wei.com>, <louhongxiang@...wei.com>
Subject: Re: [PATCH] debugfs:fix repeated output problem with `logdump -O -n
 <num_trans>`

friendly ping...

On 2022/11/15 16:29, lihaoxiang (F) wrote:
> Previously, patch 6e4cc3d5eeb2dfaa055e652b5390beaa6c3d05da introduces
> the function of printing the specified number of logs. But there exists
> a shortage when n is larger than the total number of logs, it dumped the
> duplicated records circulately.
> 
> For example, the disk sda only has three records, but using instruction logdump
> -On5, it would output the result as follow:
> ----------------------------------------------------------------------
> Journal starts at block 1, transaction 6
> Found expected sequence 6, type 1 (descriptor block) at block 1
> Found expected sequence 6, type 2 (commit block) at block 4
> No magic number at block 5: end of journal.
> Found sequence 2 (not 7) at block 7: end of journal.
> Found expected sequence 2, type 2 (commit block) at block 7
> Found sequence 3 (not 8) at block 8: end of journal.
> Found expected sequence 3, type 1 (descriptor block) at block 8
> Found sequence 3 (not 8) at block 15: end of journal.
> Found expected sequence 3, type 2 (commit block) at block 15
> Found sequence 6 (not 9) at block 1: end of journal.       <---------begin loop
> Found expected sequence 6, type 1 (descriptor block) at block 1
> Found sequence 6 (not 9) at block 4: end of journal.
> Found expected sequence 6, type 2 (commit block) at block 4
> Found sequence 2 (not 10) at block 7: end of journal.
> Found expected sequence 2, type 2 (commit block) at block 7
> logdump: short read (read 0, expected 1024) while reading journal
> 
> In this commit, we solve the problem above by exiting dumping if the
> blocknr had already encountered, displayed the total number of logs
> that the disk only possessed.
> 
> Signed-off-by: lihaoxiang <lihaoxiang9@...wei.com>
> ---
>  debugfs/logdump.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/debugfs/logdump.c b/debugfs/logdump.c
> index 614414e5..036b50ba 100644
> --- a/debugfs/logdump.c
> +++ b/debugfs/logdump.c
> @@ -376,6 +376,7 @@ static void dump_journal(char *cmdname, FILE *out_file,
>  	journal_header_t	*header;
>  	tid_t			transaction;
>  	unsigned int		blocknr = 0;
> +	unsigned int		first_transaction_blocknr;
>  	int			fc_done;
>  	__u64			total_len;
>  	__u32			maxlen;
> @@ -470,10 +471,18 @@ static void dump_journal(char *cmdname, FILE *out_file,
>  			blocknr = 1;
>  	}
> 
> +	first_transaction_blocknr = blocknr;
> +
>  	while (1) {
>  		if (dump_old && (dump_counts != -1) && (cur_counts >= dump_counts))
>  			break;
> 
> +		if ((blocknr == first_transaction_blocknr) &&
> +		    (cur_counts != 0) && dump_old && (dump_counts != -1)) {
> +			fprintf(out_file, "Dump all %lld journal records.\n", cur_counts);
> +			break;
> +		}
> +
>  		retval = read_journal_block(cmdname, source,
>  				((ext2_loff_t) blocknr) * blocksize,
>  				buf, blocksize);