Re: AFS-Cache hickups with Ubuntu and Kernel 6.17
Dave Botsch <[email protected]> Tue, 10 Mar 2026 00:45:00 -0400
| Newsgroups | gmane.comp.file-systems.openafs.general |
|---|---|
| Message-ID | <19cd61004e0.27fb.7e7218444f75578ebec1b7dbb1486319@cnf.cornell.edu> |
This is a multi-part message in MIME format. --19cd61005386b7627fbcc35b18 Content-Type: text/plain; format=flowed; charset="us-ascii" Content-Transfer-Encoding: quoted-printable What is the Linux kernel change so that we can check for this change bein= g=20 back ported into other kernels that have a lesser version number? Thanks. On March 9, 2026 9:47:58 PM Cheyenne Wills <[email protected]> wrote: > I believe that I found the problem that can result in stale dentries. > The fix should be fairly simple. An old configure test was masking a > change in the Linux kernel. > > -- > Cheyenne Wills > [email protected] > > > > On Mon, 9 Mar 2026 14:29:29 +0100 > Gaja Sophie Peters <[email protected]> wrote: >> 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 >> >> _______________________________________________ >> OpenAFS-info mailing list >> [email protected] >> https://lists.openafs.org/mailman/listinfo/openafs-info > > _______________________________________________ > OpenAFS-info mailing list > [email protected] > https://lists.openafs.org/mailman/listinfo/openafs-info --19cd61005386b7627fbcc35b18 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.= w3.org/TR/html4/loose.dtd"> <html> <body> <div dir=3D"auto"> <div dir=3D"auto">What is the Linux kernel change so that we can check for = this change being back ported into other kernels that have a lesser version= number? Thanks.</div><div dir=3D'auto'><br></div> <div id=3D"aqm-original" style=3D"color: black;"> <div dir=3D"auto">On March 9, 2026 9:47:58 PM Cheyenne Wills <cwills@sin= enomine.net> wrote:</div> <div><br></div> <blockquote type=3D"cite" class=3D"gmail_quote" style=3D"margin: 0 0 0 0.75= ex; border-left: 1px solid #808080; padding-left: 0.75ex;"> <div dir=3D"auto">I believe that I found the problem that can result in sta= le dentries.</div> <div dir=3D"auto">The fix should be fairly simple. An old configure t= est was masking a</div> <div dir=3D"auto">change in the Linux kernel.</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">-- </div> <div dir=3D"auto">Cheyenne Wills</div> <div dir=3D"auto">[email protected]</div> <div dir=3D"auto"><br></div> <div dir=3D"auto"><br></div> <div dir=3D"auto"><br></div> <div dir=3D"auto">On Mon, 9 Mar 2026 14:29:29 +0100</div> <div dir=3D"auto">Gaja Sophie Peters <[email protected]>= ; wrote:</div> <blockquote type=3D"cite" class=3D"gmail_quote" style=3D"margin: 0 0 0 0.75= ex; border-left: 1px solid #0099CC; padding-left: 0.75ex;"> <div dir=3D"auto">TLDR: OpenAFS on Ubuntu with kernel 6.17 is in certain ci= rcumstances</div> <div dir=3D"auto">not updating the Cache on file-deletion or file-creation = happening on</div> <div dir=3D"auto">a different machine, the only fix is: echo 3 >/proc/sy= s/vm/drop_caches</div> <div dir=3D"auto"><br></div> <div dir=3D"auto"><br></div> <div dir=3D"auto">Long version: We discovered a problem with the recent adv= ent of the </div> <div dir=3D"auto">kernel 6.17 as the newest "hardware enablement kernel" in= Ubuntu</div> <div dir=3D"auto">24.04. Basically the existence or non-existence of a file= is not</div> <div dir=3D"auto">correctly reflected by the AFS-Cache, when a file is dele= ted or</div> <div dir=3D"auto">created on another machine after the file was seen (or no= t) on the</div> <div dir=3D"auto">current machine.</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">### first test: file deletion not propagated</div> <div dir=3D"auto">#this command on a different machine# echo X >test-afs= </div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">X</div> <div dir=3D"auto">#this command on the other machine# rm test-afs</div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">X</div> <div dir=3D"auto">$ fs flushall</div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">cat: test-afs: Input/output error</div> <div dir=3D"auto">#as root# echo 3 >/proc/sys/vm/drop_caches</div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">cat: test-afs: No such file or directory</div> <div dir=3D"auto">### second test: file creation not propagated</div> <div dir=3D"auto">#this command on a different machine# echo Y >test-afs= </div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">cat: test-afs: No such file or directory</div> <div dir=3D"auto">$ fs flushall</div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">cat: test-afs: No such file or directory</div> <div dir=3D"auto">#as root# echo 3 >/proc/sys/vm/drop_caches</div> <div dir=3D"auto">$ cat test-afs</div> <div dir=3D"auto">Y</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">We haven't yet tried to pinpoint at which exact kernel-ve= rsion that </div> <div dir=3D"auto">problem got introduced, but the Ubuntu-kernels 6.8 and 6.= 14 are </div> <div dir=3D"auto">unaffected, the Ubuntu-kernel 6.17 is affected (kAFS on 6= .17 is </div> <div dir=3D"auto">unaffected). It doesn't make a difference, if the OpenAFS= -version is </div> <div dir=3D"auto">1.8.14 with the Ubuntu-patches for Kernel 6.17 or if it i= s OpenAFS</div> <div dir=3D"auto">1.8.15</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">The file server hosting the volume was originally 1.8.13.= 2-1 from</div> <div dir=3D"auto">Debian Trixie, but updating to 1.8.15 does not change any= thing,</div> <div dir=3D"auto">either.</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">Is this known? Any idea how to deal with it?</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">Greetings,</div> <div dir=3D"auto">Gaja Peters</div> <div dir=3D"auto"><br></div> <div dir=3D"auto">_______________________________________________</div> <div dir=3D"auto">OpenAFS-info mailing list</div> <div dir=3D"auto">[email protected]</div> <div dir=3D"auto">https://lists.openafs.org/mailman/listinfo/openafs-info</= div> </blockquote> <div dir=3D"auto"><br></div> <div dir=3D"auto">_______________________________________________</div> <div dir=3D"auto">OpenAFS-info mailing list</div> <div dir=3D"auto">[email protected]</div> <div dir=3D"auto">https://lists.openafs.org/mailman/listinfo/openafs-info</= div> </blockquote> </div><div dir=3D"auto"><br></div> </div></body> </html> --19cd61005386b7627fbcc35b18--