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Message-ID: <20240424-befund-unantastbar-9b0154bec6e7@brauner>
Date: Wed, 24 Apr 2024 19:01:32 +0200
From: Christian Brauner <brauner@...nel.org>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc: amir73il@...il.com, hu1.chen@...el.com, miklos@...redi.hu,
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
On Tue, Apr 02, 2024 at 07:18:05PM -0700, Vinicius Costa Gomes wrote:
> Hi,
>
> Changes from RFC v3:
> - Removed the warning "fixes" patches, as they could hide potencial
> bugs (Christian Brauner);
> - Added "cred-specific" macros (Christian Brauner), from my side,
> added a few '_' to the guards to signify that the newly introduced
> helper macros are preferred.
> - Changed a few guard() to scoped_guard() to fix the clang (17.0.6)
> compilation error about 'goto' bypassing variable initialization;
>
> Link to RFC v3:
>
> https://lore.kernel.org/r/20240216051640.197378-1-vinicius.gomes@intel.com/
>
> Changes from RFC v2:
> - Added separate patches for the warnings for the discarded const
> when using the cleanup macros: one for DEFINE_GUARD() and one for
> DEFINE_LOCK_GUARD_1() (I am uncertain if it's better to squash them
> together);
> - Reordered the series so the backing file patch is the first user of
> the introduced helpers (Amir Goldstein);
> - Change the definition of the cleanup "class" from a GUARD to a
> LOCK_GUARD_1, which defines an implicit container, that allows us
> to remove some variable declarations to store the overriden
> credentials (Amir Goldstein);
> - Replaced most of the uses of scoped_guard() with guard(), to reduce
> the code churn, the remaining ones I wasn't sure if I was changing
> the behavior: either they were nested (overrides "inside"
> overrides) or something calls current_cred() (Amir Goldstein).
>
> New questions:
> - The backing file callbacks are now called with the "light"
> overriden credentials, so they are kind of restricted in what they
> can do with their credentials, is this acceptable in general?
Until we grow additional users, I think yes. Just needs to be
documented.
> - 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.
Do you have a reproducer? Do you have a splat from dmesg?
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