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

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Date:   Thu, 4 May 2023 09:17:49 +0100
From:   John Garry <john.g.garry@...cle.com>
To:     Bart Van Assche <bvanassche@....org>, 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 03/05/2023 19:48, Bart Van Assche wrote:
> 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.

ok

> 
>> +
>>   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.

So you think that && means that (rq->cmd_flags & REQ_ATOMIC) will be 
auto a bool. Fine, I can change that.

Thanks,
John