Cmnt: [SRU][j/gke][f/gke][PATCH 0/1] Make new NFS cache behaviour opt-in

[Thadeu Lima de Souza Cascardo]

On Thu, Jun 01, 2023 at 03:09:36PM -0400, Khalid Elmously wrote:
> BugLink: https://bugs.launchpad.net/bugs/2022098
> 
> The fix to LP #2003053 has caused massively increased NFS server access in some use-cases, which caused severe performance degradation to the point of being unusable.
> 
> The solution to this issue, at least temporarily and at least for linux-gke, is to make the new behaviour optional using the "nfs_fasc=1" module parameter. Without this parameter specified, (or specified as =0) will keep the old behaviour.
> 
> 
> Thanks Thadeu for the feedback and the original inspiration for this fix.
> 

Which was actually based on Chengen Du's original patch. I think he should have
been credited as well, and involved in the matter too.

> 
> Testing:
>  - Used a slightly modified version of this patch (which simply logs whether the new or the old behaviour is taking effect) on an NFS client to confirm that 'modprobe nfs' and 'modprobe nfs nfs_fasc=0' maintain the old behaviour, and that 'modprobe nfs nfs_fasc=1' implements the new cache behaviour.
> 

This is very limited testing, given we have a test cases for #2003053 which
should have been taken into account with both nfs_fasc=0 and nfs_fasc=1.

Hopefully we get this right before this gets shipped in all our kernels.

Cascardo.

> 
> Regresion potential:
>  - Regression potential is considered low considering the scope of the change and is limited to NFS only.
> 
> 
> 
> 
> Khalid Elmously (1):
>   UBUNTU: SAUCE: Make NFS file-access stale cache behaviour opt-in
> 
>  fs/nfs/dir.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> -- 
> 2.34.1
> 
> 
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