Bug#1128861: linux: when serving NFS, client attempts to lock served files fail with "No locks available"

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From	Philip Hands <phil@hands.com>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1128861: linux: when serving NFS, client attempts to lock served files fail with "No locks available"
Date	Mon, 23 Feb 2026 20:40:02 +0100
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Cross-posted to 2 groups.

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Source: linux
Version: 6.12.57-1
Severity: normal

The setup we have on openqa.debian.net and it's openqa-worker machines is that
the workers have a read-only NFS mount of a share containing the .iso images
that are used for booting the test VMs.

All kernels that I have available since 6.12.48 (6.12.57 6.12.69 6.12.73 &
6.18.5) cause the workers to fail when they try to apply a "consistent read"
lock, giving the error message: No locks available

One can demonstrate that by running this on the NFS client:

  $ flock -e -w 4 /var/lib/openqa/factory/iso/xfce_sid_20260223T140607Z.iso sleep 1
  flock: /var/lib/openqa/factory/iso/xfce_sid_20260223T140607Z.iso: No locks available

meanwhile, running that flock on the server works fine.

BTW Here are the journals from booting various versions of the kernel:

  https://hands.com/~phil/tmp/openqa-nfs-lock-issue/

Cheers, Phil.

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Thread

Bug#1128861: linux: when serving NFS, client attempts to lock served files fail with "No locks available" Philip Hands <phil@hands.com> - 2026-02-23 20:40 +0100
  Bug#1128861: Acknowledgement (linux: when serving NFS, client attempts to lock served files fail with "No locks available") Philip Hands <phil@hands.com> - 2026-02-23 23:30 +0100
  Bug#1128861: Acknowledgement (linux: when serving NFS, client attempts to lock served files fail with "No locks available") Philip Hands <phil@hands.com> - 2026-02-24 00:40 +0100
    Bug#1128861: Acknowledgement (linux: when serving NFS, client attempts to lock served files fail with "No locks available") Philip Hands <phil@hands.com> - 2026-02-24 01:30 +0100
  Bug#1128861: Revert 18744bc56b0ec appears to resolve it Tj <tj.iam.tj@proton.me> - 2026-02-24 01:50 +0100
  Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available Tj <tj.iam.tj@proton.me> - 2026-02-24 03:20 +0100
    Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available Tj <tj.iam.tj@proton.me> - 2026-02-24 14:00 +0100
    Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available Thorsten Leemhuis <regressions@leemhuis.info> - 2026-02-27 11:10 +0100
      Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available Salvatore Bonaccorso <carnil@debian.org> - 2026-03-04 11:40 +0100
    Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available Sasha Levin <sashal@kernel.org> - 2026-03-04 16:50 +0100
  Processed: Re: Bug#1128861: Regression: Missing check in  nfsd_permission() causes -ENOLCK No locks available "Debian Bug Tracking System" <owner@bugs.debian.org> - 2026-03-04 11:40 +0100
  Bug#1128861: [PATCH] lockd: fix TEST handling when not all permissions are available. Ben Hutchings <ben@decadent.org.uk> - 2026-03-25 21:40 +0100

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