linux-kernel - Re: [PATCH 19/21] scsi: sd: Add WRITE_ATOMIC

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Date:   Mon, 2 Oct 2023 12:36:08 +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,
        jejb@...ux.ibm.com, martin.petersen@...cle.com, djwong@...nel.org,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        chandan.babu@...cle.com, dchinner@...hat.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, tytso@....edu, jbongio@...gle.com,
        linux-api@...r.kernel.org
Subject: Re: [PATCH 19/21] scsi: sd: Add WRITE_ATOMIC_16 support

On 29/09/2023 18:59, Bart Van Assche wrote:
> On 9/29/23 03:27, 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;
>> +}
> 
> Please store the 'dld' value in the GROUP NUMBER field. See e.g.
> sd_setup_rw16_cmnd().

Are you sure that WRITE ATOMIC (16) supports dld?

> 
>> @@ -1139,6 +1156,7 @@ 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;
> 
> Please leave out the superfluous "!!".

ok, fine.

Thanks,
John