>-----Original Message----- >From: J. Bruce Fields [mailto:bfields@xxxxxxxxxxxx] >Sent: Tuesday, April 01, 2008 3:13 PM > >> >which is called from fs/nfsd/nfssvc.c:nfsd_svc() as: >> > >> > error = nfsd_racache_init(2*nrservs); >> > >> >where nrservs is the number of server threads. How many server >threads >> >are you >> >trying to start, and how much memory do you have? >> >> >> Yea, I have seen that codebase. The configuration file /etc/init.d/nfs >creates 8 nfs threads: >> >> root:Zeugma:/etc/init.d# ps -A |grep nfs >> 2202 ? 00:00:00 nfsd >> 2203 ? 00:00:00 nfsd >> 2204 ? 00:00:00 nfsd >> 2205 ? 00:00:00 nfsd >> 2206 ? 00:00:00 nfsd >> 2207 ? 00:00:00 nfsd >> 2208 ? 00:00:00 nfsd >> 2209 ? 00:00:00 nfsd >> root:Zeugma:/etc/init.d# free >> total used free shared buffers >cached >> Mem: 255372 34352 221020 0 2564 >18720 >> -/+ buffers/cache: 13068 242304 >> Swap: 0 0 0 >> >> >> The funny thing is that the moment I enable nfsd filesystem, the >problem >> seems to go away. > >OK, so write_svc() (hence sys_nfsservctl()) is getting garbage. Hm. Yea, indeed. So I did some digging with printks and found that the #server threads are indeed not getting correctly passed on to the kernel. This I attributed, as you have suggested, to some memory corruption. >The structure that's passed in to the kernel is: > > struct nfsctl_svc { > unsigned short svc_port; > int svc_nthreads; > }; > >Is it at all possible that userspace and the kernel could disagree about >the layout of that structure? I looked at the userspace definition of nfsctl_arg in support/include/nfs/nfs.h: struct nfsctl_arg { int ca_version; /* safeguard */ union { struct nfsctl_svc u_svc; struct nfsctl_client u_client; struct nfsctl_export u_export; struct nfsctl_uidmap u_umap; struct nfsctl_fhparm u_getfh; struct nfsctl_fdparm u_getfd; struct nfsctl_fsparm u_getfs; void *u_ptr; } u; #define ca_svc u.u_svc #define ca_client u.u_client #define ca_export u.u_export #define ca_umap u.u_umap #define ca_getfh u.u_getfh #define ca_getfd u.u_getfd #define ca_getfs u.u_getfs #define ca_authd u.u_authd }; As you can see, we have an extra u_ptr member in the union (which is the same as in the kernel: include/linux/nfsd/syscall.h). For experiment, I removed this member, recompiled nfs-utils and wala! The kernel now gets the correct value of the server thread #. I am a bit puzzled by this since u_umap member already has a char* and I think adding a void* does not change the alignment of the union. In the kernel, its presence is important since it does not have a u_umap member in its nfsctl_arg declaration: struct nfsctl_arg { int ca_version; /* safeguard */ union { struct nfsctl_svc u_svc; struct nfsctl_client u_client; struct nfsctl_export u_export; struct nfsctl_fdparm u_getfd; struct nfsctl_fsparm u_getfs; /* * The following dummy member is needed to preserve binary compatibility * on platforms where alignof(void*)>alignof(int). It's needed because * this union used to contain a member (u_umap) which contained a * pointer. */ void *u_ptr; } u; #define ca_svc u.u_svc #define ca_client u.u_client #define ca_export u.u_export #define ca_getfd u.u_getfd #define ca_getfs u.u_getfs }; Ani -- 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
