From: Jan Kara <jack@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Miklos Szeredi <miklos@szeredi.hu>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
virtio-fs@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 01/19] dax: remove block device dependencies
Date: Thu, 9 Jan 2020 12:24:47 +0100 [thread overview]
Message-ID: <20200109112447.GG27035@quack2.suse.cz> (raw)
In-Reply-To: <CAPcyv4ggoS4dWjq-1KbcuaDtroHKEi5Vu19ggJ-qgycs6w1eCA@mail.gmail.com>
On Tue 07-01-20 10:49:55, Dan Williams wrote:
> On Tue, Jan 7, 2020 at 10:33 AM Vivek Goyal <vgoyal@redhat.com> wrote:
> > W.r.t partitioning, bdev_dax_pgoff() seems to be the pain point where
> > dax code refers back to block device to figure out partition offset in
> > dax device. If we create a dax object corresponding to "struct block_device"
> > and store sector offset in that, then we could pass that object to dax
> > code and not worry about referring back to bdev. I have written some
> > proof of concept code and called that object "dax_handle". I can post
> > that code if there is interest.
>
> I don't think it's worth it in the end especially considering
> filesystems are looking to operate on /dev/dax devices directly and
> remove block entanglements entirely.
>
> > IMHO, it feels useful to be able to partition and use a dax capable
> > block device in same way as non-dax block device. It will be really
> > odd to think that if filesystem is on /dev/pmem0p1, then dax can't
> > be enabled but if filesystem is on /dev/mapper/pmem0p1, then dax
> > will work.
>
> That can already happen today. If you do not properly align the
> partition then dax operations will be disabled. This proposal just
> extends that existing failure domain to make all partitions fail to
> support dax.
Well, I have some sympathy with the sysadmin that has /dev/pmem0 device,
decides to create partitions on it for whatever (possibly misguided)
reason and then ponders why the hell DAX is not working? And PAGE_SIZE
partition alignment is so obvious and widespread that I don't count it as a
realistic error case sysadmins would be pondering about currently.
So I'd find two options reasonably consistent:
1) Keep status quo where partitions are created and support DAX.
2) Stop partition creation altogether, if anyones wants to split pmem
device further, he can use dm-linear for that (i.e., kpartx).
But I'm not sure if the ship hasn't already sailed for option 2) to be
feasible without angry users and Linus reverting the change.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-01-09 11:25 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 17:57 [PATCH v3 00/19][RFC] virtio-fs: Enable DAX support Vivek Goyal
2019-08-21 17:57 ` [PATCH 01/19] dax: remove block device dependencies Vivek Goyal
2019-08-26 11:51 ` Christoph Hellwig
2019-08-27 16:38 ` Vivek Goyal
2019-08-28 6:58 ` Christoph Hellwig
2019-08-28 17:58 ` Vivek Goyal
2019-08-28 22:53 ` Dave Chinner
2019-08-29 0:04 ` Dan Williams
2019-08-29 9:32 ` Christoph Hellwig
2019-12-16 18:10 ` Vivek Goyal
2020-01-07 12:51 ` Christoph Hellwig
2020-01-07 14:22 ` Dan Williams
2020-01-07 17:07 ` Darrick J. Wong
2020-01-07 17:29 ` Dan Williams
2020-01-07 18:01 ` Vivek Goyal
2020-01-07 18:07 ` Dan Williams
2020-01-07 18:33 ` Vivek Goyal
2020-01-07 18:49 ` Dan Williams
2020-01-07 19:02 ` Darrick J. Wong
2020-01-07 19:46 ` Dan Williams
2020-01-07 23:38 ` Dan Williams
2020-01-09 11:24 ` Jan Kara [this message]
2020-01-09 20:03 ` Dan Williams
2020-01-10 12:36 ` Christoph Hellwig
2020-01-14 20:31 ` Vivek Goyal
2020-01-14 20:39 ` Dan Williams
2020-01-14 21:28 ` Vivek Goyal
2020-01-14 22:23 ` Dan Williams
2020-01-15 19:56 ` Vivek Goyal
2020-01-15 20:17 ` Dan Williams
2020-01-15 21:08 ` Jeff Moyer
2020-01-16 18:09 ` Dan Williams
2020-01-16 18:39 ` Vivek Goyal
2020-01-16 19:09 ` Dan Williams
2020-01-16 19:23 ` Vivek Goyal
2020-02-11 17:33 ` Vivek Goyal
2020-01-15 9:03 ` Jan Kara
2019-08-21 17:57 ` [PATCH 02/19] dax: Pass dax_dev to dax_writeback_mapping_range() Vivek Goyal
2019-08-26 11:53 ` Christoph Hellwig
2019-08-26 20:33 ` Vivek Goyal
2019-08-26 20:58 ` Vivek Goyal
2019-08-26 21:33 ` Dan Williams
2019-08-28 6:58 ` Christoph Hellwig
2020-01-03 14:12 ` Vivek Goyal
2020-01-03 18:12 ` Dan Williams
2020-01-03 18:18 ` Dan Williams
2020-01-03 18:33 ` Vivek Goyal
2020-01-03 19:30 ` Dan Williams
2020-01-03 18:43 ` Vivek Goyal
2019-08-27 13:45 ` Jan Kara
2019-08-21 17:57 ` [PATCH 03/19] virtio: Add get_shm_region method Vivek Goyal
2019-08-21 17:57 ` [PATCH 04/19] virtio: Implement get_shm_region for PCI transport Vivek Goyal
2019-08-26 1:43 ` [Virtio-fs] " piaojun
2019-08-26 13:06 ` Vivek Goyal
2019-08-27 9:41 ` piaojun
2019-08-27 8:34 ` Cornelia Huck
2019-08-27 8:46 ` Cornelia Huck
2019-08-27 11:53 ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 05/19] virtio: Implement get_shm_region for MMIO transport Vivek Goyal
2019-08-27 8:39 ` Cornelia Huck
2019-08-27 11:54 ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 06/19] fuse, dax: add fuse_conn->dax_dev field Vivek Goyal
2019-08-21 17:57 ` [PATCH 07/19] virtio_fs, dax: Set up virtio_fs dax_device Vivek Goyal
2019-08-21 17:57 ` [PATCH 08/19] fuse: Keep a list of free dax memory ranges Vivek Goyal
2019-08-21 17:57 ` [PATCH 09/19] fuse: implement FUSE_INIT map_alignment field Vivek Goyal
2019-08-21 17:57 ` [PATCH 10/19] fuse: Introduce setupmapping/removemapping commands Vivek Goyal
2019-08-21 17:57 ` [PATCH 11/19] fuse, dax: Implement dax read/write operations Vivek Goyal
2019-08-21 19:49 ` Liu Bo
2019-08-22 12:59 ` Vivek Goyal
2019-08-21 17:57 ` [PATCH 12/19] fuse, dax: add DAX mmap support Vivek Goyal
2019-08-21 17:57 ` [PATCH 13/19] fuse: Define dax address space operations Vivek Goyal
2019-08-21 17:57 ` [PATCH 14/19] fuse, dax: Take ->i_mmap_sem lock during dax page fault Vivek Goyal
2019-08-21 17:57 ` [PATCH 15/19] fuse: Maintain a list of busy elements Vivek Goyal
2019-08-21 17:57 ` [PATCH 16/19] dax: Create a range version of dax_layout_busy_page() Vivek Goyal
2019-08-21 17:57 ` [PATCH 17/19] fuse: Add logic to free up a memory range Vivek Goyal
2019-08-21 17:57 ` [PATCH 18/19] fuse: Release file in process context Vivek Goyal
2019-08-21 17:57 ` [PATCH 19/19] fuse: Take inode lock for dax inode truncation Vivek Goyal
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