From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Subject: Re: [RFC PATCH bpf-next v2 4/4] error-injection: Support fault
 injection framework
Date: Tue, 26 Dec 2017 18:12:56 -0800
Message-ID: <20171227021255.sahkcpgyzohl5brs@ast-mbp>
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 <151427450538.32561.2776225740675148782.stgit@devbox>
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Cc: Alexei Starovoitov <ast@fb.com>, Josef Bacik <jbacik@fb.com>,
        rostedt@goodmis.org, mingo@redhat.com, davem@davemloft.net,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        ast@kernel.org, kernel-team@fb.com, daniel@iogearbox.net,
        linux-btrfs@vger.kernel.org, darrick.wong@oracle.com,
        Josef Bacik <josef@toxicpanda.com>,
        Akinobu Mita <akinobu.mita@gmail.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
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On Tue, Dec 26, 2017 at 04:48:25PM +0900, Masami Hiramatsu wrote:
> Support in-kernel fault-injection framework via debugfs.
> This allows you to inject a conditional error to specified
> function using debugfs interfaces.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  Documentation/fault-injection/fault-injection.txt |    5 +
>  kernel/Makefile                                   |    1 
>  kernel/fail_function.c                            |  169 +++++++++++++++++++++
>  lib/Kconfig.debug                                 |   10 +
>  4 files changed, 185 insertions(+)
>  create mode 100644 kernel/fail_function.c
> 
> diff --git a/Documentation/fault-injection/fault-injection.txt b/Documentation/fault-injection/fault-injection.txt
> index 918972babcd8..6243a588dd71 100644
> --- a/Documentation/fault-injection/fault-injection.txt
> +++ b/Documentation/fault-injection/fault-injection.txt
> @@ -30,6 +30,11 @@ o fail_mmc_request
>    injects MMC data errors on devices permitted by setting
>    debugfs entries under /sys/kernel/debug/mmc0/fail_mmc_request
>  
> +o fail_function
> +
> +  injects error return on specific functions by setting debugfs entries
> +  under /sys/kernel/debug/fail_function. No boot option supported.

I like it.
Could you document it a bit better?
In particular retval is configurable, but without an example no one
will be able to figure out how to use it.

I think you can drop RFC tag from the next version of these patches.
Thanks!