[dm-devel] what's up with pp_balance_units?

[k-ueda at ct.jp.nec.com]

Hi,

On Thu, 28 Apr 2005 22:36:20 +0200, christophe varoqui wrote:
> It's not default because its code path is badly inefficient.

How about "don't use callout, and set same priority for all path"
by defualt?  It's more efficient, I think.

And, I found a possible bug that pp->priority is defined as 
"unsigned int" while it's used like "int".
But, if you fix this bug, "/bin/false" doesn't work as callout
because it always fails.
So I think it will fit your policy to add a feature of
"do not use callout" and use it by default.


Bug in multipath-tools-0.4.4
============================
If priority callout is "/bin/false", in devinfo(), execute_program()
returns non-zero, since "/bin/false" exits by 1 even if "/bin/false"
terminate normally.  So, pp->priority is set by "-1".

---------------------------------------------------------------------
libmultipath/discovery.c:477:

        /*
         * get path prio
         */
        if (mask & DI_PRIO) {
                select_getprio(pp);

                if (apply_format(pp->getprio, &buff[0], pp)) {
                        condlog(0, "error formatting prio callout command");
                        pp->priority = -1;
                } else if (execute_program(buff, prio, 16)) {
                        condlog(0, "error calling out %s", buff);
                        pp->priority = -1;
                } else
                        pp->priority = atoi(prio);

                condlog(3, "prio = %u", pp->priority);
        }
---------------------------------------------------------------------

In coalesce_paths(), if "priority" of "struct path" is less than "0",
the multipath which include the path isn't mapped.
But this "if check" is always false even if it is set by "-1", since
"priority" of "struct path" is declared with "unsigned int".
Should it be declared with "int"?

---------------------------------------------------------------
multipath/main.c:713:
                if (pp1->priority < 0)
                        mpp->action = ACT_NOTHING;

multipath/main.c:738:
                        if (pp2->priority < 0)
                                mpp->action = ACT_NOTHING;
---------------------------------------------------------------

Regards,
Ky (Kiyoshi Ueda)