Date: Sun, 25 Apr 2021 20:12:27 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: freebsd-stable <freebsd-stable@freebsd.org> Subject: NFSv4 issues related to delegations and the back channel Message-ID: <YQXPR0101MB0968B0065980882C703E9F0FDD439@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM>
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Hi,=0A= =0A= A problem with the NFSv4.1/4.2 server was identified, where it=0A= erroneously bound the back channel on a new TCP connection=0A= was identified, that could break the Linux client.=0A= Fixing this has cascaded into a fair number of patches to=0A= make the back channel work correctly. Since use of delegations=0A= requires a working back channel, this mostly affects use of=0A= delegations.=0A= =0A= I now think I have resolved everything and the patches should=0A= be in "main" and then stable/12 and stable/13 in a few weeks.=0A= They should all be in the next FreeBSD12 and FreeBSD 13 releases.=0A= =0A= Until you have a patched NFSv4 client and/or server system, I=0A= am making the following recommendations to avoid trouble:=0A= - Do not use the Linux "nconnects" mount option.=0A= - Do not enable delegations. (This also applies to a patched=0A= NFSv4.1/4.2 server if any of your clients are Linux systems=0A= running a kernel version prior to 5.3.)=0A= - For the NFSv4 server, leave vfs.nfsd.issue_delegations =3D=3D 0.=0A= - For the NFSv4 client, do not run the nfscbd(8) daemon.=0A= =0A= Most of the issues are NFSv4.1/4.2 specific, but some affect=0A= NFSv4.0 as well, so the above recommendations apply to all=0A= NFSv4 versions.=0A= =0A= Fortunately, delegations seldom improve performance,=0A= so following the above recommendations should not be=0A= a big problem.=0A= =0A= rick=0A=
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