From: Vinicius Tinti <viniciustinti@gmail.com>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Christoph Hellwig <hch@infradead.org>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH v3] ext4: Enable code path when DX_DEBUG is set
Date: Wed, 3 Feb 2021 06:51:26 -0300 [thread overview]
Message-ID: <CALD9WKz-Jgmz7inOghv37ZwzD_8sVPT_-YZUX5FpQE5aKrDJJg@mail.gmail.com> (raw)
In-Reply-To: <YBo29/SdgCkZZinT@mit.edu>
On Wed, Feb 3, 2021 at 2:39 AM Theodore Ts'o <tytso@mit.edu> wrote:
>
> On Tue, Feb 02, 2021 at 04:28:37PM +0000, Vinicius Tinti wrote:
> > Clang with -Wunreachable-code-aggressive is being used to try to find
> > unreachable code that could cause potential bugs. There is no plan to
> > enable it by default.
> >
> > The following code was detected as unreachable:
> >
> > fs/ext4/namei.c:831:17: warning: code will never be executed
> > [-Wunreachable-code]
> > unsigned n = count - 1;
> > ^~~~~
> > fs/ext4/namei.c:830:7: note: silence by adding parentheses to mark code as
> > explicitly dead
> > if (0) { // linear search cross check
> > ^
> > /* DISABLES CODE */ ( )
> >
> > This has been present since commit ac27a0ec112a ("[PATCH] ext4: initial
> > copy of files from ext3") and fs/ext3 had it present at the beginning of
> > git history. It has not been changed since.
> >
> > This patch moves the code to a new function `htree_rep_invariant_check`
> > which only performs the check when DX_DEBUG is set. This allows the
> > function to be used in other parts of the code.
> >
> > Suggestions from: Andreas, Christoph, Nathan, Nick and Ted.
> >
> > Signed-off-by: Vinicius Tinti <viniciustinti@gmail.com>
>
> Thanks, applied, although I rewrote the commit description:
>
> ext4: factor out htree rep invariant check
>
> This patch moves some debugging code which is used to validate the
> hash tree node when doing a binary search of an htree node into a
> separate function, which is disabled by default (since it is only used
> by developers when they are modifying the htree code paths).
>
> In addition to cleaning up the code to make it more maintainable, it
> silences a Clang compiler warning when -Wunreachable-code-aggressive
> is enabled. (There is no plan to enable this warning by default, since
> there it has far too many false positives; nevertheless, this commit
> reduces one of the many false positives by one.)
>
> The original description buried the lede, in terms of the primary
> reason why I think the change was worthwhile (although I know you have
> different priorities than mine :-).
>
> Thanks for working to find a way to improve the code in a way that
> makes both of us happy!
Thanks for the feedback.
And thanks for all the ones who reviewed.
> - Ted
next prev parent reply other threads:[~2021-02-03 9:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 18:58 [PATCH] ext4: Remove unreachable code Vinicius Tinti
2021-01-30 1:35 ` Nathan Chancellor
2021-01-30 6:42 ` Andreas Dilger
2021-02-01 0:31 ` [PATCH v2] ext4: Enable code path when DX_DEBUG is set Vinicius Tinti
2021-02-01 0:48 ` Nathan Chancellor
2021-02-01 12:49 ` Christoph Hellwig
2021-02-01 16:15 ` Vinicius Tinti
2021-02-01 17:13 ` Theodore Ts'o
2021-02-01 18:41 ` Vinicius Tinti
2021-02-01 20:45 ` Andreas Dilger
2021-02-01 21:09 ` Theodore Ts'o
2021-02-01 21:16 ` Nick Desaulniers
2021-02-01 21:38 ` Theodore Ts'o
2021-02-01 21:41 ` Nick Desaulniers
2021-02-01 22:05 ` Vinicius Tinti
2021-02-01 22:48 ` Theodore Ts'o
2021-02-01 23:09 ` Nick Desaulniers
2021-02-02 8:05 ` Christoph Hellwig
2021-02-02 16:28 ` [PATCH v3] " Vinicius Tinti
2021-02-03 5:39 ` Theodore Ts'o
2021-02-03 9:51 ` Vinicius Tinti [this message]
2021-02-01 16:58 ` [PATCH v2] " Theodore Ts'o
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