Erros de Jenkins: java.io.IOException: não é possível excluir

Question

Eu tenho um servidor Jenkins no Ubuntu 14.04 no EC2. Recentemente, o tempo de carregamento das páginas piorou muito.

Quando examinei os logs, notei que o Jenkins não pode excluir os links para atalhos como lastUnsuccessfulBuild e lastStableBuild depois que as compilações são concluídas:

Jun 26, 2014 5:23:59 AM hudson.model.Run execute
INFO: tests_functional #4948 main build action completed: SUCCESS
Jun 26, 2014 5:23:59 AM jenkins.model.PeepholePermalink updateCache
WARNING: Failed to update hudson.model.FreeStyleProject@1ce01735[tests_functional] lastStableBuild permalink for tests_functional #4948
java.io.IOException: Unable to delete /var/lib/jenkins/jobs/tests_functional/builds/lastStableBuild
    at hudson.util.AtomicFileWriter.commit(AtomicFileWriter.java:112)
    at jenkins.model.PeepholePermalink.writeSymlink(PeepholePermalink.java:200)
    at jenkins.model.PeepholePermalink.updateCache(PeepholePermalink.java:150)
    at jenkins.model.PeepholePermalink$RunListenerImpl.onCompleted(PeepholePermalink.java:237)
    at hudson.model.listeners.RunListener.fireCompleted(RunListener.java:199)
    at hudson.model.Run.execute(Run.java:1783)
    at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
    at hudson.model.ResourceController.execute(ResourceController.java:88)
    at hudson.model.Executor.run(Executor.java:234)

...

Jun 26, 2014 7:26:34 AM jenkins.model.PeepholePermalink updateCache
WARNING: Failed to update hudson.model.FreeStyleProject@7caf5092[location_server_commit] lastUnsuccessfulBuild permalink for location_server_commit #889
java.io.IOException: Unable to delete /var/lib/jenkins/jobs/location_server_commit/builds/lastUnsuccessfulBuild
    at hudson.util.AtomicFileWriter.commit(AtomicFileWriter.java:112)
    at jenkins.model.PeepholePermalink.writeSymlink(PeepholePermalink.java:200)
    at jenkins.model.PeepholePermalink.updateCache(PeepholePermalink.java:150)
    at jenkins.model.PeepholePermalink$RunListenerImpl.onCompleted(PeepholePermalink.java:237)
    at hudson.model.listeners.RunListener.fireCompleted(RunListener.java:199)
    at hudson.model.Run.execute(Run.java:1783)
    at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
    at hudson.model.ResourceController.execute(ResourceController.java:88)
    at hudson.model.Executor.run(Executor.java:234)

A propriedade do arquivo em /var/lib/jenkins/jobs/tests_functional parece certa:

drwxr-xr-x   2 jenkins nogroup 4.0K Apr  8 20:53 lastSuccessful
drwxr-xr-x   2 jenkins nogroup 4.0K Apr  8 20:53 lastStable
-rw-r--r--   1 jenkins nogroup 2.7K Jun 12 16:00 config.xml
-rw-r--r--   1 jenkins nogroup    5 Jun 26 05:23 nextBuildNumber
drwxr-xr-x   8 jenkins nogroup 4.0K Jun 26 05:23 workspace
-rw-r--r--   1 jenkins nogroup  542 Jun 26 06:02 disk-usage.xml
drwxr-xr-x 207 jenkins nogroup  12K Jun 26 07:44 builds
-rw-r--r--   1 jenkins nogroup  291 Jun 26 07:45 scm-polling.log

Alguma ideia do que há de errado com Jenkins e como posso corrigi-lo?