Hello, Steve Dickson. you wrote at 23:54:00 on 2008-12-18 : >"Re: why there is a complex sync between /var/lib/nfs/etab in user-modeand export_table in kernel mode?" >lioupayphone wrote: >> Hello, linux-nfs >> >> i found that an entry in /var/lib/nfs/etab (etab for abbr) was written to exprot_table of kernel-mode via a proc-file when a client requests mnt this entry. >> when the entry in export_table of kernel-mode was expired (eg : reached its expiration time), an upcall machanism is able to make sure that the newly entry from etab of user-mode was written to export_table of kernel-mode. ie, the entry in export_table of kernel-mode was updated by the one of user-mode. >> >> if the content listed above is true, i think linux nfs is too complex. and why not remove the etab from user-mode? >> in a word, i think it is easy to just maintain export_table of kernel-mode. we can directly scan /etc/exports and make up a complete export-entry, then write it to the export_table of kernel-mode. the entries in export_table of kernel-mode would never be expired unless we explicitly remove it from the export_table of kernel-mode (a proc MUST be provided for meeting this requirement). >> >> when the server is rebooted and nfsd proc-filesystem is ready, just re-do "scanning the /etc/exports and make up complete export-entries, then write them into export_table of kernel-mode". >> >> i aims to 1) remove the complex upcall machanism , 2) get rid of the couple of /var/lib/nfs/etab in user-mode and export_table in kernel-mode. >> >> anyone can give me some suggestions? or points out what's wrong i am. >The /var/lib/nfs/etab file is the way the exportfs command communicates >with the mountd daemon. 'exportfs -ar' causes the exports in /etc/exports >to be parsed and written to the etab. When a mount request is received >mountd reads the etab to build its internal export table. Ultimately >when the mount is successful, the kernel writes the mount to >/proc/net/rpc/nfsd.export/content. > >So that's how the etab fits in the grand scheme of things... > >I believe what you are suggesting is simply pumping down >all the exports in /etc/exports directly to the kernel. >This ideas has been discussed and I believe the conclusion >we came to was; why pump down thousands of exports that >may or may not used. Dynamically building the kernel export >data just seem to make more sense in our case... > >I hope this helps... :-) thank you very much. i think your comments are very clear and very helpful for me. but i still think rpc.mountd is somewhat complex. we all know that a daemon in user-mode is likely to be killed. rpc.mountd is no exception. once rpc.mountd was killed, there are no chance for the export_table to be updated via upcall. It cannot be denied that putting the etab into kernel mode is wastful for memory. but i still think it is an easy and stable method. thanks again. :-) > >steved. > Best Regards! lioupayphone -- 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
