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References: <20190506182736.21064-1-evgreen@chromium.org> <20190506182736.21064-2-evgreen@chromium.org>
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From:   Gwendal Grignou <gwendal@chromium.org>
Date:   Tue, 7 May 2019 09:46:53 -0700
Message-ID: <CAPUE2utMUPmOntOsgV5+dOeQtVPu_LJ4vJCHD=G6L=h3cgakvA@mail.gmail.com>
Subject: Re: [PATCH v5 1/2] loop: Report EOPNOTSUPP properly
To:     Evan Green <evgreen@chromium.org>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Martin K Petersen <martin.petersen@oracle.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Alexis Savery <asavery@chromium.org>,
        Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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Reviewed-by: Gwendal Grignou <gwendal@chromium.org>

On Mon, May 6, 2019 at 11:30 AM Evan Green <evgreen@chromium.org> wrote:
>
> Properly plumb out EOPNOTSUPP from loop driver operations, which may
> get returned when for instance a discard operation is attempted but not
> supported by the underlying block device. Before this change, everything
> was reported in the log as an I/O error, which is scary and not
> helpful in debugging.
>
> Signed-off-by: Evan Green <evgreen@chromium.org>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>
> Changes in v5: None
> Changes in v4: None
> Changes in v3:
> - Updated tags
>
> Changes in v2:
> - Unnested error if statement (Bart)
>
>  drivers/block/loop.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index bf1c61cab8eb..bbf21ebeccd3 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -458,7 +458,9 @@ static void lo_complete_rq(struct request *rq)
>
>         if (!cmd->use_aio || cmd->ret < 0 || cmd->ret == blk_rq_bytes(rq) ||
>             req_op(rq) != REQ_OP_READ) {
> -               if (cmd->ret < 0)
> +               if (cmd->ret == -EOPNOTSUPP)
> +                       ret = BLK_STS_NOTSUPP;
> +               else if (cmd->ret < 0)
>                         ret = BLK_STS_IOERR;
>                 goto end_io;
>         }
> @@ -1892,7 +1894,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
>   failed:
>         /* complete non-aio request */
>         if (!cmd->use_aio || ret) {
> -               cmd->ret = ret ? -EIO : 0;
> +               if (ret == -EOPNOTSUPP)
> +                       cmd->ret = ret;
> +               else
> +                       cmd->ret = ret ? -EIO : 0;
>                 blk_mq_complete_request(rq);
>         }
>  }
> --
> 2.20.1
>