TLDR: OpenAFS on Ubuntu with kernel 6.17 is in certain circumstances not
updating the Cache on file-deletion or file-creation happening on a
different machine, the only fix is: echo 3 >/proc/sys/vm/drop_caches
Long version: We discovered a problem with the recent advent of the
kernel 6.17 as the newest "hardware enablement kernel" in Ubuntu 24.04.
Basically the existence or non-existence of a file is not correctly
reflected by the AFS-Cache, when a file is deleted or created on another
machine after the file was seen (or not) on the current machine.
### first test: file deletion not propagated
#this command on a different machine# echo X >test-afs
$ cat test-afs
X
#this command on the other machine# rm test-afs
$ cat test-afs
X
$ fs flushall
$ cat test-afs
cat: test-afs: Input/output error
#as root# echo 3 >/proc/sys/vm/drop_caches
$ cat test-afs
cat: test-afs: No such file or directory
### second test: file creation not propagated
#this command on a different machine# echo Y >test-afs
$ cat test-afs
cat: test-afs: No such file or directory
$ fs flushall
$ cat test-afs
cat: test-afs: No such file or directory
#as root# echo 3 >/proc/sys/vm/drop_caches
$ cat test-afs
Y
We haven't yet tried to pinpoint at which exact kernel-version that
problem got introduced, but the Ubuntu-kernels 6.8 and 6.14 are
unaffected, the Ubuntu-kernel 6.17 is affected (kAFS on 6.17 is
unaffected). It doesn't make a difference, if the OpenAFS-version is
1.8.14 with the Ubuntu-patches for Kernel 6.17 or if it is OpenAFS 1.8.15
The file server hosting the volume was originally 1.8.13.2-1 from Debian
Trixie, but updating to 1.8.15 does not change anything, either.
Is this known? Any idea how to deal with it?
Greetings,
Gaja Peters
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