linux-kernel - Re: [PATCH v2 1/2] selftests/resctrl: Fix schemata write error check

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Date:   Wed, 30 Aug 2023 13:49:18 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Wieczor-Retman, Maciej" <maciej.wieczor-retman@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
        <shuah@...nel.org>, <fenghua.yu@...el.com>
CC:     <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v2 1/2] selftests/resctrl: Fix schemata write error check

Hi Maciej,

On 8/28/2023 2:56 AM, Wieczor-Retman, Maciej wrote:
> Writing bitmasks to the schemata can fail when the bitmask doesn't
> adhere to some constraints defined by what a particular CPU supports.
> Some example of constraints are max length or having contiguous bits.
> The driver should properly return errors when any rule concerning
> bitmask format is broken.
> 
> Resctrl FS returns error codes from fprintf() only when fclose() is
> called. Current error checking scheme allows invalid bitmasks to be
> written into schemata file and the selftest doesn't notice because the
> fclose() error code isn't checked.
> 
> Substitute fopen(), flose() and fprintf() with open(), close() and
> write() to avoid error code buffering between fprintf() and fclose().
> 
> Add newline to the end of the schema string so it satisfies rdt
> schemata writing requirements.

I am not sure how to interpret the above because existing code already
adds a newline to the end of the schema when the buffer is written to
the schemata file. Also please use "resctrl schemata" since RDT is
Intel specific and does not use schemata terminology.

> 
> Remove newline character from the schemat string after writing it to
> the schemata file so it prints correctly before function return.

schemat -> "schema" or "schemata"?

> Pass the string generated with strerror() to the "reason" buffer so
> the error message is more verbose. Extend "reason" buffer so it can hold
> longer messages.
> 
> Changelog v2:
> - Rewrite patch message.
> - Double "reason" buffer size to fit longer error explanation.
> - Redo file interactions with syscalls instead of stdio functions.
> 

Please place the above "Changelog v2" snippet below the "---" lines below.
This is text that should not end up in the kernel log.

> Signed-off-by: Wieczor-Retman, Maciej <maciej.wieczor-retman@...el.com>
> ---

(list of changes should go here)

Reinette



Reinette