To use a NFS-root for UDP jumbo frames the kernel on the client need to bring up interface with MTU set to 9000 bytes - otherwise it cannot contact server with jumbo frames enabled (nfs server not responding, still trying) and cannot boot. Added a kernel parameter named 'ipmtu' which can be used to specify initial MTU size when booting via nfsroot.
Signed-off-by: Mariusz Bialonczyk <[EMAIL PROTECTED]> diff -Nru linux-2.6.21.1-orig/Documentation/kernel-parameters.txt linux-2.6.21.1/Documentation/kernel-parameters.txt --- linux-2.6.21.1-orig/Documentation/kernel-parameters.txt 2007-04-27 23:49:26.000000000 +0200 +++ linux-2.6.21.1/Documentation/kernel-parameters.txt 2007-07-01 18:47:11.000000000 +0200 @@ -720,6 +720,9 @@ ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards See comment before ip2_setup() in drivers/char/ip2.c. + ipmtu= [IP_PNP] + See Documentation/nfsroot.txt. + ips= [HW,SCSI] Adaptec / IBM ServeRAID controller See header of drivers/scsi/ips.c. diff -Nru linux-2.6.21.1-orig/Documentation/nfsroot.txt linux-2.6.21.1/Documentation/nfsroot.txt --- linux-2.6.21.1-orig/Documentation/nfsroot.txt 2007-04-27 23:49:26.000000000 +0200 +++ linux-2.6.21.1/Documentation/nfsroot.txt 2007-07-01 19:02:40.000000000 +0200 @@ -153,6 +153,16 @@ Default: any +ipmtu=<mtu_value> + + This parameter tells the kernel to override default MTU size to specified + <mtu_value>. Useful in cases where NFS server have jumbo frames enabled and + client can't connect via UDP because of default MTU value (in ethernet + usually 1500 bytes). With this option before bringing interface up, kernel + will set the passed MTU size. In case of NFS-root booting server and client + can use UDP jumbo frames (NFS's rsize and wsize set to 8192 for instance). + + 3.) Boot Loader diff -Nru linux-2.6.21.1-orig/net/ipv4/ipconfig.c linux-2.6.21.1/net/ipv4/ipconfig.c --- linux-2.6.21.1-orig/net/ipv4/ipconfig.c 2007-04-27 23:49:26.000000000 +0200 +++ linux-2.6.21.1/net/ipv4/ipconfig.c 2007-07-01 15:44:44.000000000 +0200 @@ -113,6 +113,8 @@ */ int ic_set_manually __initdata = 0; /* IPconfig parameters set manually */ +unsigned int ic_mtu __initdata = 0; /* IPconfig MTU parameter: 0 - defaults, other - override */ + static int ic_enable __initdata = 0; /* IP config enabled? */ /* Protocol choice */ @@ -209,6 +211,11 @@ able &= ic_proto_enabled; if (ic_proto_enabled && !able) continue; + if (ic_mtu > 0) + { + printk(KERN_ERR "IP-Config: Overriding %s MTU to %d bytes\n", dev->name, ic_mtu); + dev->mtu = ic_mtu; + } oflags = dev->flags; if (dev_change_flags(dev, oflags | IFF_UP) < 0) { printk(KERN_ERR "IP-Config: Failed to open %s\n", dev->name); @@ -1506,5 +1513,14 @@ return ip_auto_config_setup(addrs); } +static int __init mtu_config_setup(char *str) +{ + if (!str) + return 0; + ic_mtu = simple_strtoul(str, &str, 0); + return 1; +} + __setup("ip=", ip_auto_config_setup); +__setup("ipmtu=", mtu_config_setup); __setup("nfsaddrs=", nfsaddrs_config_setup); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/