linux-kernel - can anyone explain the meaning of improvement of try

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Sat, 29 Jun 2024 10:54:15 +0000
From: lin jia <chinasjtu@....com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Thomas Weißschuh  <thomas@...ch.de>
Subject: can anyone explain the meaning of improvement of try_attach function
 in sysctl.c?

Hi all:
   I've been reading the sysctl part of the Linux kernel source code( 3.3.8) recently and encountered some issues. I'm not sure who I can ask for help.
   In sysctl.c ,  the function of __register_sysctl_paths is to register a sysctl hierarchy,  I am confused by the function " try_attach", 

/* see if attaching q to p would be an improvement */
static void try_attach(struct ctl_table_header *p, struct ctl_table_header *q)

what is the meaning of "improvement",  I don’t know the matching standard for the entry in the list

another question is , why not break when variable is_better and not_in_parent is true, so as to save time,  when I config about 2k~4k net device objects in system,  "register_net_sysctl_table" cost considerable time.

For example 

	struct ctl_table *to = p->ctl_table, *by = q->ctl_table;
	struct ctl_table *next;
	int is_better = 0;
	int not_in_parent = !p->attached_by;

	while ((next = is_branch_in(by, to)) != NULL) {
		if (by == q->attached_by)
			is_better = 1;
		if (to == p->attached_by)
			not_in_parent = 1;
		by = by->child;
		to = next->child;
        《-----------------   if(is_better && not_in_parent) break;

	}

	if (is_better && not_in_parent) {
		q->attached_by = by;
		q->attached_to = to;
		q->parent = p;
	}
} 

Thanks to all.