From: Dan Williams <dan.j.williams@intel.com>
To: Pankaj Gupta <pagupta@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>,
Qemu Developers <qemu-devel@nongnu.org>,
linux-nvdimm <linux-nvdimm@ml01.01.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
virtualization@lists.linux-foundation.org,
Linux ACPI <linux-acpi@vger.kernel.org>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-xfs <linux-xfs@vger.kernel.org>, Jan Kara <jack@suse.cz>,
Stefan Hajnoczi <stefanha@redhat.com>,
Rik van Riel <riel@surriel.com>,
Nitesh Narayan Lal <nilal@redhat.com>,
Kevin Wolf <kwolf@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Ross Zwisler <zwisler@kernel.org>,
Vishal L Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
David Hildenbrand <david@redhat.com>, jmoyer <jmoyer@redhat.com>,
Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
lcapitulino@redhat.com, Igor Mammedov <imammedo@redhat.com>,
Eric Blake <eblake@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag
Date: Wed, 9 Jan 2019 09:02:07 -0800 [thread overview]
Message-ID: <CAPcyv4jsa709BVPAx_BT5eFrODf-PUPOZ4aguDsjZVawVXTVHQ@mail.gmail.com> (raw)
In-Reply-To: <20190109135024.14093-4-pagupta@redhat.com>
On Wed, Jan 9, 2019 at 5:53 AM Pankaj Gupta <pagupta@redhat.com> wrote:
>
> This patch adds 'DAXDEV_BUFFERED' flag which is set
> for virtio pmem corresponding nd_region. This later
> is used to disable MAP_SYNC functionality for ext4
> & xfs filesystem.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
> drivers/dax/super.c | 17 +++++++++++++++++
> drivers/nvdimm/pmem.c | 3 +++
> drivers/nvdimm/region_devs.c | 7 +++++++
> drivers/virtio/pmem.c | 1 +
> include/linux/dax.h | 9 +++++++++
> include/linux/libnvdimm.h | 6 ++++++
> 6 files changed, 43 insertions(+)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f3..9128740 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -167,6 +167,8 @@ enum dax_device_flags {
> DAXDEV_ALIVE,
> /* gate whether dax_flush() calls the low level flush routine */
> DAXDEV_WRITE_CACHE,
> + /* flag to disable MAP_SYNC for virtio based host page cache flush */
> + DAXDEV_BUFFERED,
> };
>
> /**
> @@ -335,6 +337,21 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
> }
> EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
>
> +void virtio_pmem_host_cache(struct dax_device *dax_dev, bool wc)
> +{
> + if (wc)
> + set_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> + else
> + clear_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache);
The "write_cache" property was structured this way because it can
conceivably change at runtime. The MAP_SYNC capability should be
static and never changed after init.
> +bool virtio_pmem_host_cache_enabled(struct dax_device *dax_dev)
> +{
> + return test_bit(DAXDEV_BUFFERED, &dax_dev->flags);
> +}
> +EXPORT_SYMBOL_GPL(virtio_pmem_host_cache_enabled);
Echoing Darrick and Jan this is should be a generic property of a
dax_device and not specific to virtio. I don't like the "buffered"
designation as that's not accurate. There may be hardware reasons why
a dax_device is not synchronous, like a requirement to flush a
write-pending queue or otherwise notify the device of new writes.
I would just have a dax_synchronous() helper and a DAXDEV_SYNC flag. I
would also modify alloc_dax() to take a flags argument so that the
capability can be instantiated when the dax_device is allocated.
next prev parent reply other threads:[~2019-01-09 17:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 13:50 [PATCH v3 0/5] kvm "virtio pmem" device Pankaj Gupta
2019-01-09 13:50 ` [PATCH v3 1/5] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-01-09 13:50 ` [PATCH v3 2/5] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-01-09 13:50 ` [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag Pankaj Gupta
2019-01-09 17:02 ` Dan Williams [this message]
2019-01-09 18:21 ` Pankaj Gupta
2019-01-09 14:46 ` [Qemu-devel] [PATCH v3 0/5] kvm "virtio pmem" device Pankaj Gupta
2019-01-09 14:47 Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag Pankaj Gupta
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