kern/86319: support a "noac" NFS mount flag to turn off the
attribute cache
Erez Zadok
ezk at am-utils.org
Sun Sep 18 21:30:04 PDT 2005
>Number: 86319
>Category: kern
>Synopsis: support a "noac" NFS mount flag to turn off the attribute cache
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Mon Sep 19 04:30:03 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator: Erez Zadok
>Release: 5.4 and 6.0
>Organization:
Stony Brook University
>Environment:
All versions of freebsd up to and including 6.0.
>Description:
To turn off the NFS attribute cache in FreeBSD, one has to set the following four flags to zero in struct nfs_args:
nfs_args->acregmin = 0;
nfs_args->acregmax = 0;
nfs_args->acdirmin = 0;
nfs_args->acdirmax = 0;
In addition, you have to turn on four flags to tell the kernel that you indeed want it to use your values for the above four flags:
nfs_args->flags |= \
(NFSMNT_ACREGMIN|NFSMNT_ACREGMAX|NFSMNT_ACDIRMIN|NFSMNT_ACDIRMAX);
This is rather cumbersome and also confusing because some users may be used to what other OSs do: just setting the four fields suffices. For that reason, some OSs like Solaris provide a convenience flag called "noac" that can be set to simply turn off the attribute cache entirely.
I would like to ask that FreeBSD support such a convenience flag "noac".
In addition, please document this flag and the current behaviour of how one turns off the attribute cache, in the mount_nfs man page.
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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