quota woes for network filesystems

[Steven French]

Linux quotas are turning out to be painful.   I have not been able to
experiment with the parms passed in from the quota calls invoked by the
common Linux/Unix quota tools (quotacheck, quotaon, quotacheck) due to bugs
in the Linux quota tools (the only source I could find for these tools was
out on the sourceforge project). Even for the new format they refuse to
handle a deviceless (network) filesystem mount properly even after
modifying the quota tools code to make the cifs vfs act like it has the
"new" quota support ala XFS.   After changing them to recognize my
filesystem name as a valid one (they hardcode the actual valid filesystem
names in the quota tools on sourceforge!) it still fails to invoke my test
code due to mismatch on devnumber (network filesystems don't have devices
that they mount).   I had been hoping to experiment with the current stub
quota routines (in preparation for adding remote quota support to cifs
filesystem in the long run)  in the bitkeeper tree a few days ago,
eventually these could call the server to get/set the quotas by specifying
a valid SID but that also requires an ...

IPC to Winbind or upcall to a user space daemon to do Linux UID to SID
translation (also upcall is needed to finish off DFS in particular the DNS
host name lookup)

And then there is always more to finish off - the ASN/SPNEGO
encoding/parsing for the kerberized sessionsetup which also will require an
interesting upcall to get a kerberos service ticket for the user from
Winbind (and perhaps pam_kerberos as another option)

And code to send more than one read request at a time in parallel to more
efficiently service readpages (this is easier than adding support for
multipage write which currently no 2.6 Linux network filesystem really does
efficiently today).




Steve French
Senior Software Engineer
Linux Technology Center - IBM Austin
phone: 512-838-2294
email: sfrench at-sign us dot ibm dot com