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Re: [PATCH] : bug fix in multipath drr code.

To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [PATCH] : bug fix in multipath drr code.
From: pravin b shelar <pravins@xxxxxxxxxxxxxx>
Date: Tue, 24 May 2005 15:27:16 +0530
Cc: netdev@xxxxxxxxxxx, "David S. Miller" <davem@xxxxxxxxxxxxx>
In-reply-to: <20050524071146.GA30995@gondor.apana.org.au>
References: <4291CBFF.6080106@calsoftinc.com> <20050523232224.GA25349@gondor.apana.org.au> <4292CDCE.2090600@calsoftinc.com> <20050524071146.GA30995@gondor.apana.org.au>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla Thunderbird 1.0.2 (X11/20050317)
Herbert Xu wrote:

On Tue, May 24, 2005 at 12:16:38PM +0530, pravin b shelar wrote:


In fact this whole MULTIPATHOLDROUTE thing can't possibly
work at all. I'd suggest that it be removed.


So I think we should ignore MULTIPATHOLDROUTE flag
in drr and rr multipath algorithms as done in random multipath algorithm.

Attached patch does same thing.

Regards,
Pravin.
Signed-off by: Pravin B. Shelar <pravins@xxxxxxxxxxxxxx>

Index: linux-2.6.12-rc4/include/net/route.h
===================================================================
--- linux-2.6.12-rc4.orig/include/net/route.h   2005-05-06 22:20:31.000000000 
-0700
+++ linux-2.6.12-rc4/include/net/route.h        2005-05-24 02:37:10.000000000 
-0700
@@ -181,9 +181,6 @@
                memcpy(&fl, &(*rp)->fl, sizeof(fl));
                fl.fl_ip_sport = sport;
                fl.fl_ip_dport = dport;
-#if defined(CONFIG_IP_ROUTE_MULTIPATH_CACHED)
-               fl.flags |= FLOWI_FLAG_MULTIPATHOLDROUTE;
-#endif
                ip_rt_put(*rp);
                *rp = NULL;
                return ip_route_output_flow(rp, &fl, sk, 0);
Index: linux-2.6.12-rc4/net/ipv4/multipath_drr.c
===================================================================
--- linux-2.6.12-rc4.orig/net/ipv4/multipath_drr.c      2005-05-06 
22:20:31.000000000 -0700
+++ linux-2.6.12-rc4/net/ipv4/multipath_drr.c   2005-05-24 02:37:10.000000000 
-0700
@@ -57,7 +57,6 @@
 
 static struct multipath_device state[MULTIPATH_MAX_DEVICECANDIDATES];
 static DEFINE_SPINLOCK(state_lock);
-static struct rtable *last_selection = NULL;
 
 static int inline __multipath_findslot(void)
 {
@@ -111,11 +110,6 @@
        .notifier_call  = drr_dev_event,
 };
 
-static void drr_remove(struct rtable *rt)
-{
-       if (last_selection == rt)
-               last_selection = NULL;
-}
 
 static void drr_safe_inc(atomic_t *usecount)
 {
@@ -144,14 +138,6 @@
        int devidx = -1;
        int cur_min_devidx = -1;
 
-               /* if necessary and possible utilize the old alternative */
-       if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
-           last_selection != NULL) {
-               result = last_selection;
-               *rp = result;
-               return;
-       }
-
        /* 1. make sure all alt. nexthops have the same GC related data */
        /* 2. determine the new candidate to be returned */
        result = NULL;
@@ -229,12 +215,10 @@
        }
 
        *rp = result;
-       last_selection = result;
 }
 
 static struct ip_mp_alg_ops drr_ops = {
        .mp_alg_select_route    =       drr_select_route,
-       .mp_alg_remove          =       drr_remove,
 };
 
 static int __init drr_init(void)
@@ -244,7 +228,7 @@
        if (err)
                return err;
 
-       err = multipath_alg_register(&drr_ops, IP_MP_ALG_RR);
+       err = multipath_alg_register(&drr_ops, IP_MP_ALG_DRR);
        if (err)
                goto fail;
 
Index: linux-2.6.12-rc4/net/ipv4/multipath_rr.c
===================================================================
--- linux-2.6.12-rc4.orig/net/ipv4/multipath_rr.c       2005-05-06 
22:20:31.000000000 -0700
+++ linux-2.6.12-rc4/net/ipv4/multipath_rr.c    2005-05-24 02:37:10.000000000 
-0700
@@ -47,29 +47,12 @@
 #include <net/checksum.h>
 #include <net/ip_mp_alg.h>
 
-#define MULTIPATH_MAX_CANDIDATES 40
-
-static struct rtable* last_used = NULL;
-
-static void rr_remove(struct rtable *rt)
-{
-       if (last_used == rt)
-               last_used = NULL;
-}
-
 static void rr_select_route(const struct flowi *flp,
                            struct rtable *first, struct rtable **rp)
 {
        struct rtable *nh, *result, *min_use_cand = NULL;
        int min_use = -1;
 
-       /* if necessary and possible utilize the old alternative */
-       if ((flp->flags & FLOWI_FLAG_MULTIPATHOLDROUTE) != 0 &&
-           last_used != NULL) {
-               result = last_used;
-               goto out;
-       }
-
        /* 1. make sure all alt. nexthops have the same GC related data
         * 2. determine the new candidate to be returned
         */
@@ -90,15 +73,12 @@
        if (!result)
                result = first;
 
-out:
-       last_used = result;
        result->u.dst.__use++;
        *rp = result;
 }
 
 static struct ip_mp_alg_ops rr_ops = {
        .mp_alg_select_route    =       rr_select_route,
-       .mp_alg_remove          =       rr_remove,
 };
 
 static int __init rr_init(void)
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