linux-kernel - Re: [External] : Re: NFS dentry caching regression? was Re: [GIT PULL] Please pull NFS client updates for Linux 6.19

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <d272dc63-a157-4dea-966f-003cefa28d2d@oracle.com>
Date: Wed, 17 Dec 2025 09:23:27 -0500
From: Anna Schumaker <anna.schumaker@...cle.com>
To: Christoph Hellwig <hch@...radead.org>,
        Trond Myklebust <trondmy@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org
Subject: Re: [External] : Re: NFS dentry caching regression? was Re: [GIT
 PULL] Please pull NFS client updates for Linux 6.19

Hi Christoph,

On 12/17/25 4:53 AM, Christoph Hellwig wrote:
> On Wed, Dec 17, 2025 at 01:32:30AM -0800, Christoph Hellwig wrote:
>> Hi all,
>>
>> the merge of this branch causes NFS lookup operation to shoot up a lot
>> for me.  And with merge I mean merge - both parent of the merge on their
>> own are fine.
>>
>> With the script below that simulates running python scripts with lots
>> of imports that was created to benchmark delegation performance, the
>> number of lookups in the measurement period shoots up from 4 to about
>> 410000, which is a bit suboptimal.  I have no idea how this could
>> happen, but it must be related to some sort of pathname lookup changes
>> I guess.  Other operations looks roughly the same.
> 
> To further pin this down, I rebased the patches from the NFS pull request
> on top of the baseline (d358e5254674b70f34c847715ca509e46eb81e6f) and
> bisected that.  This ends up in:

Thanks for reporting this, and for the reproducer script. I'll dig into this
today and try to fix what I broke!

Anna

> 
> NFS: Shortcut lookup revalidations if we have a directory delegation
>