bcachefs: bch2_print_string_as_lines()

This adds a helper for printing a large buffer one line at a time, to
avoid the 1k printk limit.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -1334,7 +1334,7 @@ void bch2_dump_trans_updates(struct btree_trans *trans)
 	struct printbuf buf = PRINTBUF;
 
 	bch2_trans_updates_to_text(&buf, trans);
-	bch_err(trans->c, "%s", buf.buf);
+	bch2_print_string_as_lines(KERN_ERR, buf.buf);
 	printbuf_exit(&buf);
 }
 
@@ -1382,11 +1382,10 @@ void __bch2_dump_trans_paths_updates(struct btree_trans *trans, bool nosort)
 	struct printbuf buf = PRINTBUF;
 
 	__bch2_trans_paths_to_text(&buf, trans, nosort);
+	bch2_trans_updates_to_text(&buf, trans);
 
-	printk(KERN_ERR "%s", buf.buf);
+	bch2_print_string_as_lines(KERN_ERR, buf.buf);
 	printbuf_exit(&buf);
-
-	bch2_dump_trans_updates(trans);
 }
 
 noinline __cold

fs/bcachefs/util.c

@@ -8,6 +8,7 @@
 
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/console.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/freezer.h>
@@ -244,6 +245,26 @@ void bch2_prt_u64_binary(struct printbuf *out, u64 v, unsigned nr_bits)
 		prt_char(out, '0' + ((v >> --nr_bits) & 1));
 }
 
+void bch2_print_string_as_lines(const char *prefix, const char *lines)
+{
+	const char *p;
+
+	if (!lines) {
+		printk("%s (null)\n", prefix);
+		return;
+	}
+
+	console_lock();
+	while (1) {
+		p = strchrnul(lines, '\n');
+		printk("%s%.*s\n", prefix, (int) (p - lines), lines);
+		if (!*p)
+			break;
+		lines = p + 1;
+	}
+	console_unlock();
+}
+
 /* time stats: */
 
 #ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT

fs/bcachefs/util.h

@@ -382,6 +382,8 @@ u64 bch2_read_flag_list(char *, const char * const[]);
 
 void bch2_prt_u64_binary(struct printbuf *, u64, unsigned);
 
+void bch2_print_string_as_lines(const char *prefix, const char *lines);
+
 #define NR_QUANTILES	15
 #define QUANTILE_IDX(i)	inorder_to_eytzinger0(i, NR_QUANTILES)
 #define QUANTILE_FIRST	eytzinger0_first(NR_QUANTILES)