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Bug 2006399 - limited reexport support kernel documentation
Summary: limited reexport support kernel documentation
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: kernel
Version: unspecified
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: nfs-maint
QA Contact: Yongcheng Yang
Michal Stubna
URL:
Whiteboard:
Depends On:
Blocks: 2121576
TreeView+ depends on / blocked
 
Reported: 2021-09-21 16:25 UTC by J. Bruce Fields
Modified: 2022-12-08 13:22 UTC (History)
10 users (show)

Fixed In Version: kernel-5.14.0-132.el9
Doc Type: No Doc Update
Doc Text:
The NFS server can now reexport an NFS filesystem from another server. This may be useful, for example, for accelerating access to rarely changing data in some cases. However, it comes with some limitations; we will need to refer users to documentation for more details.
Clone Of:
Environment:
Last Closed: 2022-11-15 10:50:59 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Gitlab redhat/centos-stream/src/kernel centos-stream-9 merge_requests 601 0 None None None 2022-03-21 21:06:49 UTC
Red Hat Issue Tracker RHELPLAN-97773 0 None None None 2021-09-21 16:25:53 UTC
Red Hat Product Errata RHSA-2022:8267 0 None None None 2022-11-15 10:51:15 UTC

Description J. Bruce Fields 2021-09-21 16:25:02 UTC 
Allow an NFS server to mount and reexport a NFS filesystem, with some limitations.

This is already supported by the RHEL9 kernel, but it could use a little testing and documentation.
Comment 1 J. Bruce Fields 2021-09-21 16:37:28 UTC 
https://lore.kernel.org/linux-nfs/20210921143259.GB21704@fieldses.org/ may be a starting point for documentation.

For upstream testing, I'm currently just reexporting and then running connectathon:

proxy# mkdir -p /exports/nfs
proxy# mount server:/exports/xfs /exports/nfs
proxy# echo "/exports/nfs/ *(rw,fsid=1234)" >/etc/exports
proxy# systemctl start nfs-server

client# mount proxy:/exports/nfs /mnt/
client# cd cthon
client# NFSTESTDIR=/mnt/TMP ./runtests -a -f

It's worth trying with various NFS versions (v3,v4,v4.1,v4.2).

The locking tests will fail on current RHEL9.  Patches to fix those last locking problems are upstream in 5.15.
Comment 2 Yongcheng Yang 2021-09-22 03:09:01 UTC 
Note to myself: the NFS re-export is marked as tech-preview in RHEL8 for now (see Bug 1972229).
Comment 3 J. Bruce Fields 2021-10-26 15:32:10 UTC 
Changing the title; I want to make *very* sure we emphasize that there are some important limitations.
Comment 4 Dave Wysochanski 2021-11-15 18:32:17 UTC 
(In reply to J. Bruce Fields from comment #1)
> https://lore.kernel.org/linux-nfs/20210921143259.GB21704@fieldses.org/ may
> be a starting point for documentation.
> 

Bruce, what do you think about pulling in the documentation commit to RHEL9.0 GA since this is a new feature and it will explain the limitations right?  Then Red Hat docs can point at the official kernel tree rather than repeating the text there.

commit dc451bbc6f54a2c7bacef7ec445718709071b61c
Author: J. Bruce Fields <bfields>
Date:   Fri Sep 10 14:42:54 2021 -0400

    nfs: reexport documentation
    
    We've supported reexport for a while but documentation is limited.  This
    is mainly a simplified version of the text I wrote for the linux-nfs
    wiki at https://wiki.linux-nfs.org/wiki/index.php/NFS_re-export.
    
    Signed-off-by: J. Bruce Fields <bfields>

diff --git a/Documentation/filesystems/nfs/index.rst b/Documentation/filesystems/nfs/index.rst
Comment 5 J. Bruce Fields 2021-11-15 21:27:27 UTC 
(In reply to Dave Wysochanski from comment #4)
> Bruce, what do you think about pulling in the documentation commit to
> RHEL9.0 GA since this is a new feature and it will explain the limitations
> right?  Then Red Hat docs can point at the official kernel tree rather than
> repeating the text there.

That sounds reasonable to me.
Comment 8 Dave Wysochanski 2022-03-18 19:37:38 UTC 
Marking for 9.1.0 for now as I'm not sure this is even going in 9.0
Comment 36 errata-xmlrpc 2022-11-15 10:50:59 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: kernel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2022:8267
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