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

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Date:   Tue, 15 Nov 2022 16:29:55 +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: [PATCH] debugfs:fix repeated output problem with `logdump -O -n
 <num_trans>`

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);
-- 
2.37.0.windows.1