Date: Thu, 4 Mar 1999 01:18:15 -0500 (EST) From: lennox@cs.columbia.edu To: FreeBSD-gnats-submit@freebsd.org Subject: kern/10381: hlfsd/NFS failure -- directory cached between users Message-ID: <199903040618.BAA01121@conrail.cs.columbia.edu>
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>Number: 10381 >Category: kern >Synopsis: hlfsd/NFS failure -- directory cached between users >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Wed Mar 3 22:20:00 PST 1999 >Closed-Date: >Last-Modified: >Originator: Jonathan Lennox >Release: FreeBSD 3.1-STABLE i386 >Organization: Columbia University Computer Science >Environment: I have two users, lennox and llennox. The following directories and symlinks exist initially: conrail $ ls -ld /var/mail lrwxr-xr-x 1 root wheel 10 Mar 3 13:23 /var/mail@ -> /mail/home conrail $ ls -ld /mail/home lrwxrwxrwx 1 root wheel 13 Mar 4 01:01 /mail/home@ -> /var/alt_mail conrail $ ls -ld /var/alt_mail drwxrwxrwt 2 root mail 512 Mar 3 13:28 /var/alt_mail/ conrail $ ls -ld ~lennox/.mailspool drwxr-xr-x 2 lennox phd 512 Mar 4 00:50 /u/zer/lennox/.mailspool/ conrail $ ls -ld ~llennox/.mailspool drwxr-xr-x 2 llennox llennox 512 Mar 4 01:01 /home/llennox/.mailspool/ >Description: When you use hlfsd, each user is supposed to see their own version of a system-wide directory -- in this case, /mail/home -- symlinked to a subdirectory of their home directory. In FreeBSD 3.1-STABLE, however (cvsup'd on March 2nd), for all users the symlink in /mail/home points to the home directory of whatever user first looked at it after hlfsd was started. The hlfsd developer (Erez Zadok, ezk@cs.columbia.edu) said that this was indicative of the NFS attribute cache not being turned off, so values are cached by the kernel, resulting in the symlink being preserved between users. hlfsd tries to turn off the NFS attribute cache so this won't happen. I'm not sure if this is an NFS problem (in turning off the cache) or an hlfsd problem (in how it tries to turn off the cache). It seems to be trying to turn it off by setting acregmin and acdirmin to 0. I'm not sure if this PR should go in kern (as an NFS problem) or in bin (as an hlfsd problem), so I guessed kern. >How-To-Repeat: I have two users, lennox and llennox, with home directories /u/zer/lennox and /home/llennox respectively. This can be repeated with any two non-root users. 1. Set up symlinks as described in "Environment" above. 2. As root, start hlfsd: conrail # /usr/sbin/hlfsd -a /var/alt_mail -l /var/log/hlfsd /mail/home .mailspool 3. Look at /mail/home as the first user: lennox@conrail$ ls -ld /mail/home lrwxrwxrwx 1 root wheel 1024 Mar 4 01:15 /mail/home@ -> /u/zer/lennox/.mailspool 4. Look at /mail/home as the second user: llennox@conrail$ ls -ld /mail/home lrwxrwxrwx 1 root wheel 1024 Mar 4 01:15 /mail/home -> /u/zer/lennox/.mailspool [ This should be /mail/home -> /home/llennox/.mailspool. ] >Fix: Don't use hlfsd -- instead play games in .profile to set $MAIL to $HOME/.mailspool. (This is not a proper fix.) Erez (Zadok, see above) has suggested that the best solution would be for FreeBSD's nfs_mount to support a 'noac' attribute, and equivalent syscall-level structures, similar to Solaris's, which turns off the NFS attribute cache entirely, rather than having to play around with the maximum and minimum cache times. >Release-Note: >Audit-Trail: >Unformatted: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message
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