Re: [PATCH] scsi/mvsas/mv_init.c: Use dma_zalloc_coherent

[John Garry]

On 04/01/2019 19:49, Souptick Joarder wrote:
> On Fri, Jan 4, 2019 at 9:34 PM John Garry <john.garry@xxxxxxxxxx> wrote:
> > On 04/01/2019 15:11, Sabyasachi Gupta wrote:
> > > On Fri, Jan 4, 2019 at 6:43 PM John Garry <john.garry@xxxxxxxxxx> wrote:
> > > > On 04/01/2019 12:48, Sabyasachi Gupta wrote:
> > > > > On Wed, Dec 19, 2018 at 6:49 PM Sabyasachi Gupta
> > > > > <sabyasachi.linux@xxxxxxxxx> wrote:
> > > > > > On Sat, Dec 1, 2018 at 6:40 PM Sabyasachi Gupta
> > > > > > <sabyasachi.linux@xxxxxxxxx> wrote:
> > > > > > > On Wed, Nov 21, 2018 at 7:18 PM Sabyasachi Gupta
> > > > > > > <sabyasachi.linux@xxxxxxxxx> wrote:
> > > > > > > > Replace dma_alloc_coherent + memset with dma_zalloc_coherent
> > > >
> > > > If you're going to make this change, then how about change these to the
> > > > managed version, so that we can avoid the explicit free'ing at driver
> > > > removal?
> > >
> > > I can't get it
> >
> > Please see dmam_alloc_coherent(). You can set __GFP_ZERO in the gfp
> > argument to memset(0).
>
> and dma_zalloc_coherent() did the same. So both are same right ? No ?

Firstly I would to say that I am not so keen on changes like this since 
(I assume) it will not be tested at all.

However, having said that, the reason to use dmam_alloc_coherent() is 
that you can also drop the dma_free_coherent() in mvs_free(). But 
changes like that would actually require some code analysis effort...

John

> > I would say that this is a more useful change.
> >
> > > > > > > > Signed-off-by: Sabyasachi Gupta <sabyasachi.linux@xxxxxxxxx>
> > > > > > >
> > > > > > > Any comment on this patch?
> > > > > >
> > > > > > Any comment on this patch?
> > > > >
> > > > > Any comment on this patch?
> > > > >
> > > > > > > > ---
> > > > > > > >  drivers/scsi/mvsas/mv_init.c | 12 ++++--------
> > > > > > > >  1 file changed, 4 insertions(+), 8 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/drivers/scsi/mvsas/mv_init.c b/drivers/scsi/mvsas/mv_init.c
> > > > > > > > index 3ac3437..495bddb 100644
> > > > > > > > --- a/drivers/scsi/mvsas/mv_init.c
> > > > > > > > +++ b/drivers/scsi/mvsas/mv_init.c
> > > > > > > > @@ -253,33 +253,29 @@ static int mvs_alloc(struct mvs_info *mvi, struct Scsi_Host *shost)
> > > > > > > >         /*
> > > > > > > >          * alloc and init our DMA areas
> > > > > > > >          */
> > > > > > > > -       mvi->tx = dma_alloc_coherent(mvi->dev,
> > > > > > > > +       mvi->tx = dma_zalloc_coherent(mvi->dev,
> > > > > > > >                                      sizeof(*mvi->tx) * MVS_CHIP_SLOT_SZ,
> > > > > > > >                                      &mvi->tx_dma, GFP_KERNEL);
> > > >
> > > > I'm guessing that this does not pass checkpatch with --strict option.
> > > >
> > > > Thanks,
> > > > John
> > >
> > > I have not not checked with --strict option
> >
> > It may warn that you're not maintaining alignment.
> >
> > > > > > > >         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_zalloc_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,
> > > > > > > > +       mvi->rx = dma_zalloc_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;
> > > > > > > >
> > > > > > > > -       mvi->slot = dma_alloc_coherent(mvi->dev,
> > > > > > > > +       mvi->slot = dma_zalloc_coherent(mvi->dev,
> > > > > > > >                                        sizeof(*mvi->slot) * slot_nr,
> > > > > > > >                                        &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,
> > > > > > > > --
> > > > > > > > 2.7.4
> > > > >
> > > > > .
> > >
> > > .
>
> .