bcachefs: Unlock trans when waiting for user input in fsck

We can't hold locks while waiting for user input, that's a deadlock.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/error.c

@@ -99,7 +99,7 @@ static enum ask_yn parse_yn_response(char *buf)
 }
 
 #ifdef __KERNEL__
-static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c)
+static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c, struct btree_trans *trans)
 {
 	struct stdio_redirect *stdio = c->stdio;
 
@@ -109,17 +109,33 @@ static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c)
 	if (!stdio)
 		return YN_NO;
 
+	if (trans)
+		bch2_trans_unlock(trans);
+
+	unsigned long unlock_long_at = trans ? jiffies + HZ * 2 : 0;
 	darray_char line = {};
 	int ret;
 
 	do {
+		unsigned long t;
 		bch2_print(c, " (y,n, or Y,N for all errors of this type) ");
+rewait:
+		t = unlock_long_at
+			? max_t(long, unlock_long_at - jiffies, 0)
+			: MAX_SCHEDULE_TIMEOUT;
+
+		int r = bch2_stdio_redirect_readline_timeout(stdio, &line, t);
+		if (r == -ETIME) {
+			bch2_trans_unlock_long(trans);
+			unlock_long_at = 0;
+			goto rewait;
+		}
 
-		int r = bch2_stdio_redirect_readline(stdio, &line);
 		if (r < 0) {
 			ret = YN_NO;
 			break;
 		}
+
 		darray_last(line) = '\0';
 	} while ((ret = parse_yn_response(line.data)) < 0);
 
@@ -130,7 +146,7 @@ static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c)
 
 #include "tools-util.h"
 
-static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c)
+static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c, struct btree_trans *trans)
 {
 	char *buf = NULL;
 	size_t buflen = 0;
@@ -326,7 +342,15 @@ int __bch2_fsck_err(struct bch_fs *c,
 				bch2_print_string_as_lines(KERN_ERR, out->buf);
 			print = false;
 
-			int ask = bch2_fsck_ask_yn(c);
+			int ask = bch2_fsck_ask_yn(c, trans);
+
+			if (trans) {
+				ret = bch2_trans_relock(trans);
+				if (ret) {
+					mutex_unlock(&c->fsck_error_msgs_lock);
+					goto err;
+				}
+			}
 
 			if (ask >= YN_ALLNO && s)
 				s->fix = ask == YN_ALLNO