netdev - Re: [net] devlink: report 0 after hitting end in region read

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Message-ID: <20200205061811.GA2159@nanopsycho>
Date:   Wed, 5 Feb 2020 07:18:11 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     netdev@...r.kernel.org, valex@...lanox.com, parav@...lanox.com
Subject: Re: [net] devlink: report 0 after hitting end in region read

Wed, Feb 05, 2020 at 12:59:50AM CET, jacob.e.keller@...el.com wrote:
>commit fdd41ec21e15 ("devlink: Return right error code in case of errors
>for region read") modified the region read code to report errors
>properly in unexpected cases.
>
>In the case where the start_offset and ret_offset match, it unilaterally
>converted this into an error. This causes an issue for the "dump"
>version of the command. In this case, the devlink region dump will
>always report an invalid argument:
>
>000000000000ffd0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>000000000000ffe0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>devlink answers: Invalid argument
>000000000000fff0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>
>This occurs because the expected flow for the dump is to return 0 after
>there is no further data.
>
>The simplest fix would be to stop converting the error code to -EINVAL
>if start_offset == ret_offset. However, avoid unnecessary work by
>checking for when start_offset is larger than the region size and
>returning 0 upfront.
>
>Fixes: fdd41ec21e15 ("devlink: Return right error code in case of errors for region read")
>Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>

Thanks!