linux-kernel - Re: [PATCH 0/3] CONFIG_VFS

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Message-ID: <CAGudoHFq2AbuvvKhhY7pOouE_jhJk5ZdkU_Dd1wYnyYHosndpA@mail.gmail.com>
Date: Wed, 5 Feb 2025 19:57:07 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: brauner@...nel.org
Cc: viro@...iv.linux.org.uk, jack@...e.cz, linux-kernel@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 0/3] CONFIG_VFS_DEBUG at last

On Wed, Feb 5, 2025 at 7:38 PM Mateusz Guzik <mjguzik@...il.com> wrote:
>
> This adds a super basic version just to get the mechanism going and
> adds sample usage.
>
> The macro set is incomplete (e.g., lack of locking macros) and
> dump_inode routine fails to dump any state yet, to be implemented(tm).
>
> I think despite the primitive state this is complete enough to start
> sprinkling warns as necessary.
>
> Mateusz Guzik (3):
>   vfs: add initial support for CONFIG_VFS_DEBUG
>   vfs: catch invalid modes in may_open
>   vfs: use the new debug macros in inode_set_cached_link()
>
>  fs/namei.c               |  2 ++
>  include/linux/fs.h       | 16 +++----------
>  include/linux/vfsdebug.h | 50 ++++++++++++++++++++++++++++++++++++++++
>  lib/Kconfig.debug        |  9 ++++++++
>  4 files changed, 64 insertions(+), 13 deletions(-)
>  create mode 100644 include/linux/vfsdebug.h
>
> --
> 2.43.0
>

The produced warn is ugly as sin:\, for example for that bad size:
[   51.433206] VFS_WARN_ON_INODE(__builtin_choose_expr((sizeof(int) ==
sizeof(*(8 ? ((void *)((long)(__builtin_strlen(link)) * 0l)) : (int
*)8))), __builtin_strlen(link), __fortify_strlen(link)) != linklen)
failed for inode ff32f7c350c8aec8

maybe there is a way to work it around, the code is literally lifted
out of mmdebug.h so they presumably have the same problem

apart from that the assert in may_open is backwards, the code normally
is not reached.

anyhow I expect to send a v2, but will wait for feedback before I do
-- 
Mateusz Guzik <mjguzik gmail.com>