list_journal: Add -n for number of entries to print

The entire journal can be too big to fit in memory in textual form,
making grep difficult: this adds an option to print a specific number of
journal entries.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/cmd_debug.c b/cmd_debug.c
index 37232481..e29ceff6 100644
--- a/cmd_debug.c
+++ b/cmd_debug.c
@@ -578,6 +578,7 @@ static void list_journal_usage(void)
 	     "\n"
 	     "Options:\n"
 	     "  -a            Read entire journal, not just dirty entries\n"
+	     "  -n            Number of journal entries to print, starting from the most recent\n"
 	     "  -h            Display this help and exit\n"
 	     "Report bugs to <linux-bcache@vger.kernel.org>");
 }
@@ -596,6 +597,7 @@ static void star_start_of_lines(char *buf)
 int cmd_list_journal(int argc, char *argv[])
 {
 	struct bch_opts opts = bch2_opts_empty();
+	u32 nr_entries = U32_MAX;
 	int opt;
 
 	opt_set(opts, nochanges,	true);
@@ -606,11 +608,15 @@ int cmd_list_journal(int argc, char *argv[])
 	opt_set(opts, keep_journal,	true);
 	opt_set(opts, read_journal_only,true);
 
-	while ((opt = getopt(argc, argv, "ah")) != -1)
+	while ((opt = getopt(argc, argv, "an:h")) != -1)
 		switch (opt) {
 		case 'a':
 			opt_set(opts, read_entire_journal, true);
 			break;
+		case 'n':
+			nr_entries = kstrtouint(optarg, 10, &nr_entries);
+			opt_set(opts, read_entire_journal, true);
+			break;
 		case 'h':
 			list_journal_usage();
 			exit(EXIT_SUCCESS);
@@ -634,6 +640,9 @@ int cmd_list_journal(int argc, char *argv[])
 		if (!p)
 			continue;
 
+		if (le64_to_cpu(p->j.seq) + nr_entries < atomic64_read(&c->journal.seq))
+			continue;
+
 		bool blacklisted =
 			bch2_journal_seq_is_blacklisted(c,
 					le64_to_cpu(p->j.seq), false);