linux-kernel - Re: [PATCH v10 4/7] dm: enable synchronous dax

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Date:   Mon, 10 Jun 2019 01:08:20 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        KVM list <kvm@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Qemu Developers <qemu-devel@...gnu.org>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        device-mapper development <dm-devel@...hat.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Christoph Hellwig <hch@...radead.org>,
        Len Brown <lenb@...nel.org>, Jan Kara <jack@...e.cz>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        lcapitulino@...hat.com, Kevin Wolf <kwolf@...hat.com>,
        Igor Mammedov <imammedo@...hat.com>,
        jmoyer <jmoyer@...hat.com>,
        Nitesh Narayan Lal <nilal@...hat.com>,
        Rik van Riel <riel@...riel.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        david <david@...morbit.com>, cohuck@...hat.com,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        yuval shaia <yuval.shaia@...cle.com>,
        Adam Borowski <kilobyte@...band.pl>, jstaron@...gle.com,
        Randy Dunlap <rdunlap@...radead.org>,
        Mike Snitzer <snitzer@...hat.com>
Subject: Re: [PATCH v10 4/7] dm: enable synchronous dax


> On Tue, May 21, 2019 at 6:43 AM Pankaj Gupta <pagupta@...hat.com> wrote:
> >
> >  This patch sets dax device 'DAXDEV_SYNC' flag if all the target
> >  devices of device mapper support synchrononous DAX. If device
> >  mapper consists of both synchronous and asynchronous dax devices,
> >  we don't set 'DAXDEV_SYNC' flag.
> >
> > Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
> > ---
> >  drivers/md/dm-table.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> > index cde3b49b2a91..1cce626ff576 100644
> > --- a/drivers/md/dm-table.c
> > +++ b/drivers/md/dm-table.c
> > @@ -886,10 +886,17 @@ static int device_supports_dax(struct dm_target *ti,
> > struct dm_dev *dev,
> >         return bdev_dax_supported(dev->bdev, PAGE_SIZE);
> >  }
> >
> > +static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
> > +                              sector_t start, sector_t len, void *data)
> > +{
> > +       return dax_synchronous(dev->dax_dev);
> > +}
> > +
> >  static bool dm_table_supports_dax(struct dm_table *t)
> >  {
> >         struct dm_target *ti;
> >         unsigned i;
> > +       bool dax_sync = true;
> >
> >         /* Ensure that all targets support DAX. */
> >         for (i = 0; i < dm_table_get_num_targets(t); i++) {
> > @@ -901,7 +908,14 @@ static bool dm_table_supports_dax(struct dm_table *t)
> >                 if (!ti->type->iterate_devices ||
> >                     !ti->type->iterate_devices(ti, device_supports_dax,
> >                     NULL))
> >                         return false;
> > +
> > +               /* Check devices support synchronous DAX */
> > +               if (dax_sync &&
> > +                   !ti->type->iterate_devices(ti, device_synchronous,
> > NULL))
> > +                       dax_sync = false;
> 
> Looks like this needs to be rebased on the current state of v5.2-rc,
> and then we can nudge Mike for an ack.

Sorry! for late reply due to vacations. I will rebase the series on v5.2-rc4 and
send a v11.

Thanks,
Pankaj
Yes, 
>