Re: Possible bug report: kernel 6.5.0/6.5.1 high load when CIFS share is mounted (cifsd-cfid-laundromat in"D" state)

Steve French
2023-09-19T03:02:10Z

> I'm not clear on the value or necessity of this "laundromat thread"

This thread is used to clean up cached directories when directory
leases are supported (in those cases directory contents, and
information needed for revalidate of directory paths can be cached
safely).

On Mon, Sep 18, 2023 at 9:20 PM Brian Pardy <brian.pardy@gmail.com> wrote:
>
> [RS removed from CC due to bounce message]
>
> On Wed, Sep 6, 2023 at 5:03 PM Brian Pardy <brian.pardy@gmail.com> wrote:
> > On Tue, Sep 5, 2023 at 9:01 PM Bagas Sanjaya <bagasdotme@gmail.com> wrote:
> > > Thanks for the regression report. But if you want to get it fixed,
> > > you have to do your part: perform bisection. See Documentation/admin-guide/bug-bisect.rst in the kernel sources for how to do that.
> > >
> > > Anyway, I'm adding it to regzbot:
> > >
> > > #regzbot ^introduced: v6.4..v6.5
> > > #regzbot title: incorrect CPU utilization report (multiplied) when mounting CIFS
> >
> > Thank you for directing me to the bug-bisect documentation. Results below:
> >
> > # git bisect bad
> > d14de8067e3f9653cdef5a094176d00f3260ab20 is the first bad commit
> > commit d14de8067e3f9653cdef5a094176d00f3260ab20
> > Author: Ronnie Sahlberg <lsahlber@redhat.com>
> > Date: Thu Jul 6 12:32:24 2023 +1000
> >
> > cifs: Add a laundromat thread for cached directories
> >
> > and drop cached directories after 30 seconds
> >
> > Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> > Signed-off-by: Steve French <stfrench@microsoft.com>
> >
> > fs/smb/client/cached_dir.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++
> > fs/smb/client/cached_dir.h | 1 +
> > 2 files changed, 68 insertions(+)
>
> Is there any further information I can provide to aid in debugging
> this issue? Should I just expect incorrect load average reporting when
> a CIFS share is mounted on any kernel >6.5.0?
>
> I'm not clear on the value or necessity of this "laundromat thread" -
> everything worked as expected before it was added - shall I just patch
> it out of my kernel builds going forward if there is no interest in
> fixing it? Is a .config option to disable it possible?

--
Thanks,

Steve