linux-kernel - Re: [PATCH v1 0/3] overlayfs: Optimize override/revert creds

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Message-ID: <87frvay47x.fsf@intel.com>
Date: Wed, 24 Apr 2024 12:01:54 -0700
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: brauner@...nel.org, amir73il@...il.com, hu1.chen@...el.com,
 malini.bhandaru@...el.com, tim.c.chen@...el.com, mikko.ylinen@...el.com,
 lizhen.you@...el.com, linux-unionfs@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] overlayfs: Optimize override/revert creds

Miklos Szeredi <miklos@...redi.hu> writes:

> On Wed, 3 Apr 2024 at 04:18, Vinicius Costa Gomes
> <vinicius.gomes@...el.com> wrote:
>
>>  - in ovl_rename() I had to manually call the "light" the overrides,
>>    both using the guard() macro or using the non-light version causes
>>    the workload to crash the kernel. I still have to investigate why
>>    this is happening. Hints are appreciated.
>
> Don't know.  Well, there's nesting (in ovl_nlink_end()) but I don't
> see why that should be an issue.
>
> I see why Amir suggested moving away from scoped guards, but that also
> introduces the possibility of subtle bugs if we don't audit every one
> of those sites carefully...
>
> Maybe patchset should be restructured to first do the
> override_creds_light() conversion without guards, and then move over
> to guards.   Or the other way round, I don't have a preference.  But
> mixing these two independent changes doesn't sound like a great idea
> in any case.

Sounds good. Here's I am thinking:

patch 1: introduce *_creds_light()
patch 2: move backing-file.c to *_creds_light()
patch 3: move overlayfs to *_creds_light()
patch 4: introduce the guard helpers
patch 5: move backing-file.c to the guard helpers
patch 6: move overlayfs to the guard helpers

(and yeah, the subject of the patches will be better than these ;-)

Is this what you had in mind?


Cheers,
-- 
Vinicius