linux-kernel - Re: [PATCH RFC 14/16] scsi: sd: Add WRITE_ATOMIC

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Message-ID: <81ce524d-6186-e016-f597-153d214036bf@acm.org>
Date:   Wed, 3 May 2023 11:48:41 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     John Garry <john.g.garry@...cle.com>, axboe@...nel.dk,
        kbusch@...nel.org, hch@....de, sagi@...mberg.me,
        martin.petersen@...cle.com, djwong@...nel.org,
        viro@...iv.linux.org.uk, brauner@...nel.org, dchinner@...hat.com,
        jejb@...ux.ibm.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, paul@...l-moore.com,
        jmorris@...ei.org, serge@...lyn.com
Subject: Re: [PATCH RFC 14/16] scsi: sd: Add WRITE_ATOMIC_16 support

On 5/3/23 11:38, John Garry wrote:
> +static blk_status_t sd_setup_atomic_cmnd(struct scsi_cmnd *cmd,
> +					sector_t lba, unsigned int nr_blocks,
> +					unsigned char flags)
> +{
> +	cmd->cmd_len  = 16;
> +	cmd->cmnd[0]  = WRITE_ATOMIC_16;
> +	cmd->cmnd[1]  = flags;
> +	put_unaligned_be64(lba, &cmd->cmnd[2]);
> +	cmd->cmnd[10] = 0;
> +	cmd->cmnd[11] = 0;
> +	put_unaligned_be16(nr_blocks, &cmd->cmnd[12]);
> +	cmd->cmnd[14] = 0;
> +	cmd->cmnd[15] = 0;
> +
> +	return BLK_STS_OK;
> +}

A single space in front of the assignment operator please.

> +
>   static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>   {
>   	struct request *rq = scsi_cmd_to_rq(cmd);
> @@ -1149,6 +1166,7 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
>   	unsigned int nr_blocks = sectors_to_logical(sdp, blk_rq_sectors(rq));
>   	unsigned int mask = logical_to_sectors(sdp, 1) - 1;
>   	bool write = rq_data_dir(rq) == WRITE;
> +	bool atomic_write = !!(rq->cmd_flags & REQ_ATOMIC) && write;

Isn't the !! superfluous in the above expression? I have not yet seen 
any other kernel code where a flag test is used in a boolean expression 
and where !! occurs in front of the flag test.

Thanks,

Bart.