bcachefs: Fix fsck warnings from bkey validation

__bch2_fsck_err() warns if the current task has a btree_trans object and
it wasn't passed in, because if it has to prompt for user input it has
to be able to unlock it.

But plumbing the btree_trans through bkey_validate(), as well as
transaction restarts, is problematic - so instead make bkey fsck errors
FSCK_AUTOFIX, which doesn't need to warn.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/error.c

@@ -239,7 +239,19 @@ int __bch2_fsck_err(struct bch_fs *c,
 	if (!c)
 		c = trans->c;
 
-	WARN_ON(!trans && bch2_current_has_btree_trans(c));
+	/*
+	 * Ugly: if there's a transaction in the current task it has to be
+	 * passed in to unlock if we prompt for user input.
+	 *
+	 * But, plumbing a transaction and transaction restarts into
+	 * bkey_validate() is problematic.
+	 *
+	 * So:
+	 * - make all bkey errors AUTOFIX, they're simple anyways (we just
+	 *   delete the key)
+	 * - and we don't need to warn if we're not prompting
+	 */
+	WARN_ON(!(flags & FSCK_AUTOFIX) && !trans && bch2_current_has_btree_trans(c));
 
 	if ((flags & FSCK_CAN_FIX) &&
 	    test_bit(err, c->sb.errors_silent))

fs/bcachefs/error.h

@@ -184,7 +184,7 @@ do {									\
 		ret = -BCH_ERR_fsck_delete_bkey;			\
 		goto fsck_err;						\
 	}								\
-	int _ret = __bch2_bkey_fsck_err(c, k, FSCK_CAN_FIX,		\
+	int _ret = __bch2_bkey_fsck_err(c, k, FSCK_CAN_FIX|FSCK_AUTOFIX,\
 				BCH_FSCK_ERR_##_err_type,		\
 				_err_msg, ##__VA_ARGS__);		\
 	if (_ret != -BCH_ERR_fsck_fix &&				\