From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>, Christoph Hellwig <hch@lst.de>,
Vishal Verma <vishal.l.verma@intel.com>,
Dave Jiang <dave.jiang@intel.com>,
Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
Ira Weiny <ira.weiny@intel.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Matthew Wilcox <willy@infradead.org>,
device-mapper development <dm-devel@redhat.com>,
Linux NVDIMM <nvdimm@lists.linux.dev>,
linux-s390 <linux-s390@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 4/5] dax: remove the copy_from_iter and copy_to_iter methods
Date: Mon, 13 Dec 2021 09:23:18 +0100 [thread overview]
Message-ID: <20211213082318.GB21462@lst.de> (raw)
In-Reply-To: <CAPcyv4g4_yFqDeS+pnAZOxcB=Ua+iArK5mqn0iMG4PX6oL=F_A@mail.gmail.com>
On Sun, Dec 12, 2021 at 06:44:26AM -0800, Dan Williams wrote:
> On Fri, Dec 10, 2021 at 6:17 AM Vivek Goyal <vgoyal@redhat.com> wrote:
> > Going forward, I am wondering should virtiofs use flushcache version as
> > well. What if host filesystem is using DAX and mapping persistent memory
> > pfn directly into qemu address space. I have never tested that.
> >
> > Right now we are relying on applications to do fsync/msync on virtiofs
> > for data persistence.
>
> This sounds like it would need coordination with a paravirtualized
> driver that can indicate whether the host side is pmem or not, like
> the virtio_pmem driver. However, if the guest sends any fsync/msync
> you would still need to go explicitly cache flush any dirty page
> because you can't necessarily trust that the guest did that already.
Do we? The application can't really know what backend it is on, so
it sounds like the current virtiofs implementation doesn't really, does it?
next prev parent reply other threads:[~2021-12-13 8:23 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-09 6:38 devirtualize kernel access to DAX Christoph Hellwig
2021-12-09 6:38 ` [PATCH 1/5] uio: remove copy_from_iter_flushcache() and copy_mc_to_iter() Christoph Hellwig
2021-12-12 14:22 ` Dan Williams
2021-12-13 8:27 ` Christoph Hellwig
2021-12-09 6:38 ` [PATCH 2/5] dax: simplify dax_synchronous and set_dax_synchronous Christoph Hellwig
2021-12-09 21:03 ` Pankaj Gupta
2021-12-12 14:23 ` Dan Williams
2021-12-09 6:38 ` [PATCH 3/5] dax: remove the DAXDEV_F_SYNC flag Christoph Hellwig
2021-12-12 14:24 ` Dan Williams
2021-12-13 8:40 ` Pankaj Gupta
2021-12-09 6:38 ` [PATCH 4/5] dax: remove the copy_from_iter and copy_to_iter methods Christoph Hellwig
2021-12-10 14:16 ` Vivek Goyal
2021-12-12 14:44 ` Dan Williams
2021-12-13 8:23 ` Christoph Hellwig [this message]
2021-12-14 14:22 ` Vivek Goyal
2021-12-14 16:41 ` Dan Williams
2021-12-14 20:32 ` Vivek Goyal
2021-12-14 23:43 ` Dan Williams
2021-12-15 15:52 ` Vivek Goyal
2021-12-15 16:46 ` Dan Williams
2021-12-15 10:30 ` Stefan Hajnoczi
2021-12-15 15:43 ` Vivek Goyal
2021-12-15 17:27 ` Stefan Hajnoczi
2021-12-13 16:17 ` Vivek Goyal
2021-12-12 14:39 ` Dan Williams
2021-12-13 8:24 ` Christoph Hellwig
2021-12-09 6:38 ` [PATCH 5/5] dax: always use _copy_mc_to_iter in dax_copy_to_iter Christoph Hellwig
2021-12-10 14:05 ` Vivek Goyal
2021-12-12 14:48 ` Dan Williams
2021-12-13 8:20 ` Christoph Hellwig
2021-12-13 16:43 ` Dan Williams
2021-12-14 13:59 ` Vivek Goyal
2021-12-12 15:03 ` Dan Williams
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