On Apr 21, 2015, at 4:37 AM, Mason <slash.tmp@xxxxxxx> wrote: > Hello, > > On 01/04/2015 11:55, Mason wrote: > >> My embedded system is supposed to mount the rootfs via NFS. >> https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt >> >> So I set these options in my kernel .config >> >> CONFIG_IP_PNP=y >> CONFIG_IP_PNP_DHCP=y >> CONFIG_ROOT_NFS=y >> CONFIG_NFS_V4=y >> >> But it didn't work, the system would panic after a long time out >> (around 95 seconds) >> >> [ 98.567037] VFS: Unable to mount root fs via NFS, trying floppy. >> [ 98.573238] Freeing unused kernel memory: 144K (c0332000 - c0356000) >> [ 98.579698] Kernel panic - not syncing: No working init found. >> Try passing init= option to kernel. See Linux Documentation/init.txt for guidance. >> >> I then enabled NFSv2 and NFSv3, and then it worked. >> >> When I was debugging the problem, I ran across NFS_DEF_OPTIONS >> in fs/nfs/nfsroot.c >> >> #define NFS_DEF_OPTIONS "vers=2,udp,rsize=4096,wsize=4096" >> >> IIUC, we are explicitly requesting NFSv2? >> >> Would that explain why it fails when NFSv2 support is not compiled in? >> >> Would it make sense to use version 3? >> (So NFSv2 is not needed just to load the rootfs.) > > I saw commit 4251c94833aa (NFS: Revert NFSROOT default mount options) > which states: > > Last fall we removed the ad hoc mount option parser in > fs/nfs/nfsroot.c in favor of using the main parser in fs/nfs/super.c > (see commit 56463e50 "NFS: Use super.c for NFSROOT mount option > parsing"). That commit changed the default NFSROOT mount options to > be the same as those employed by user space mounts. > As it turns out, these new default mount options are not tolerated by > many embedded systems. So far these problems have been due to > specific behavior of certain embedded NICs. The NFS community does > not have such hardware on hand for running tests. > Commit 53d47375 recently introduced a clean way to specify default > mount options for NFSROOT, so we can now easily restore the > traditional defaults for NFSROOT: > vers=2,udp,rsize=4096,wsize=4096 > This should revert the new default NFSROOT mount options introduced > with commit 56463e50. > > I guess this explains why vers=3 is not the default? > > I'm now wondering how to override the mount options on the boot command > line. Looking more closely at commit 53d473758053 (NFS: NFSROOT should > default to "proto=udp") nothing jumps out at me. > > My current boot command line is > "root=/dev/nfs ip=:::::eth0:dhcp rdinit=/none console=ttyS0,115200 mem=512M earlyprintk" > > Looking at the documentation > https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt > I don't see where the protocol version is specified. > > Where am I supposed to add the vers=3 option? Let’s try that again. Specifying “vers=3” in the nfs-options section of the nfsroot= boot parameter should work. -- Chuck Lever chuck[dot]lever[at]oracle[dot]com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
