linux-kernel - Re: [PATCH v2] scsi: Don't call memset after dma_alloc

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Message-ID: <8f829bd7-fb2b-44af-44ea-130b08c1fd70@gmail.com>
Date:   Mon, 24 Aug 2020 22:52:52 +0100
From:   Alex Dewar <alex.dewar90@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     GR-QLogic-Storage-Upstream@...vell.com, jejb@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        martin.petersen@...cle.com, njavali@...vell.com
Subject: Re: [PATCH v2] scsi: Don't call memset after dma_alloc_coherent()

On 2020-08-21 00:49, Alex Dewar wrote:
> dma_alloc_coherent() already zeroes memory, so the extra call to
> memset() is unnecessary.
>
> Issue identified with Coccinelle.
>
> Signed-off-by: Alex Dewar <alex.dewar90@...il.com>
Gentle ping? I've just realised that this is the one we want, not the v1 
I just replied to.
> ---
> v2: I've noticed a few other places in the scsi subsystem with this
> pattern, so lets fix them all with one patch.
> ---
>   drivers/scsi/mpt3sas/mpt3sas_base.c | 1 -
>   drivers/scsi/mvsas/mv_init.c        | 4 ----
>   drivers/scsi/pmcraid.c              | 1 -
>   drivers/scsi/qla2xxx/qla_mbx.c      | 2 --
>   4 files changed, 8 deletions(-)
>
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
> index b66d3f9b717f..36b6c0d67353 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_base.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
> @@ -5259,7 +5259,6 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc)
>   		_base_release_memory_pools(ioc);
>   		goto retry_allocation;
>   	}
> -	memset(ioc->request, 0, sz);
>   
>   	if (retry_sz)
>   		ioc_err(ioc, "request pool: dma_alloc_coherent succeed: hba_depth(%d), chains_per_io(%d), frame_sz(%d), total(%d kb)\n",
> diff --git a/drivers/scsi/mvsas/mv_init.c b/drivers/scsi/mvsas/mv_init.c
> index 978f5283c883..6aa2697c4a15 100644
> --- a/drivers/scsi/mvsas/mv_init.c
> +++ b/drivers/scsi/mvsas/mv_init.c
> @@ -246,19 +246,16 @@ static int mvs_alloc(struct mvs_info *mvi, struct Scsi_Host *shost)
>   				     &mvi->tx_dma, GFP_KERNEL);
>   	if (!mvi->tx)
>   		goto err_out;
> -	memset(mvi->tx, 0, sizeof(*mvi->tx) * MVS_CHIP_SLOT_SZ);
>   	mvi->rx_fis = dma_alloc_coherent(mvi->dev, MVS_RX_FISL_SZ,
>   					 &mvi->rx_fis_dma, GFP_KERNEL);
>   	if (!mvi->rx_fis)
>   		goto err_out;
> -	memset(mvi->rx_fis, 0, MVS_RX_FISL_SZ);
>   
>   	mvi->rx = dma_alloc_coherent(mvi->dev,
>   				     sizeof(*mvi->rx) * (MVS_RX_RING_SZ + 1),
>   				     &mvi->rx_dma, GFP_KERNEL);
>   	if (!mvi->rx)
>   		goto err_out;
> -	memset(mvi->rx, 0, sizeof(*mvi->rx) * (MVS_RX_RING_SZ + 1));
>   	mvi->rx[0] = cpu_to_le32(0xfff);
>   	mvi->rx_cons = 0xfff;
>   
> @@ -267,7 +264,6 @@ static int mvs_alloc(struct mvs_info *mvi, struct Scsi_Host *shost)
>   				       &mvi->slot_dma, GFP_KERNEL);
>   	if (!mvi->slot)
>   		goto err_out;
> -	memset(mvi->slot, 0, sizeof(*mvi->slot) * slot_nr);
>   
>   	mvi->bulk_buffer = dma_alloc_coherent(mvi->dev,
>   				       TRASH_BUCKET_SIZE,
> diff --git a/drivers/scsi/pmcraid.c b/drivers/scsi/pmcraid.c
> index aa9ae2ae8579..d99568fdf4af 100644
> --- a/drivers/scsi/pmcraid.c
> +++ b/drivers/scsi/pmcraid.c
> @@ -4716,7 +4716,6 @@ static int pmcraid_allocate_host_rrqs(struct pmcraid_instance *pinstance)
>   			return -ENOMEM;
>   		}
>   
> -		memset(pinstance->hrrq_start[i], 0, buffer_size);
>   		pinstance->hrrq_curr[i] = pinstance->hrrq_start[i];
>   		pinstance->hrrq_end[i] =
>   			pinstance->hrrq_start[i] + PMCRAID_MAX_CMD - 1;
> diff --git a/drivers/scsi/qla2xxx/qla_mbx.c b/drivers/scsi/qla2xxx/qla_mbx.c
> index 226f1428d3e5..e00f604bbf7a 100644
> --- a/drivers/scsi/qla2xxx/qla_mbx.c
> +++ b/drivers/scsi/qla2xxx/qla_mbx.c
> @@ -4925,8 +4925,6 @@ qla25xx_set_els_cmds_supported(scsi_qla_host_t *vha)
>   		return QLA_MEMORY_ALLOC_FAILED;
>   	}
>   
> -	memset(els_cmd_map, 0, ELS_CMD_MAP_SIZE);
> -
>   	/* List of Purex ELS */
>   	cmd_opcode[0] = ELS_FPIN;
>   	cmd_opcode[1] = ELS_RDP;