From: Jan Kara <jack@suse.cz>
To: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
linux-btrfs@vger.kernel.org, kilobyte@angband.pl,
linux-fsdevel@vger.kernel.org, jack@suse.cz, david@fromorbit.com,
willy@infradead.org, hch@lst.de, dsterba@suse.cz,
nborisov@suse.com, linux-nvdimm@lists.01.org
Subject: Re: [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes
Date: Tue, 28 May 2019 11:17:29 +0200 [thread overview]
Message-ID: <20190528091729.GD9607@quack2.suse.cz> (raw)
In-Reply-To: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com>
On Mon 27-05-19 16:25:41, Shiyang Ruan wrote:
> On 5/23/19 7:51 PM, Goldwyn Rodrigues wrote:
> > >
> > > Hi,
> > >
> > > I'm working on reflink & dax in XFS, here are some thoughts on this:
> > >
> > > As mentioned above: the second iomap's offset and length must match the
> > > first. I thought so at the beginning, but later found that the only
> > > difference between these two iomaps is @addr. So, what about adding a
> > > @saddr, which means the source address of COW extent, into the struct iomap.
> > > The ->iomap_begin() fills @saddr if the extent is COW, and 0 if not. Then
> > > handle this @saddr in each ->actor(). No more modifications in other
> > > functions.
> >
> > Yes, I started of with the exact idea before being recommended this by Dave.
> > I used two fields instead of one namely cow_pos and cow_addr which defined
> > the source details. I had put it as a iomap flag as opposed to a type
> > which of course did not appeal well.
> >
> > We may want to use iomaps for cases where two inodes are involved.
> > An example of the other scenario where offset may be different is file
> > comparison for dedup: vfs_dedup_file_range_compare(). However, it would
> > need two inodes in iomap as well.
> >
> Yes, it is reasonable. Thanks for your explanation.
>
> One more thing RFC:
> I'd like to add an end-io callback argument in ->dax_iomap_actor() to update
> the metadata after one whole COW operation is completed. The end-io can
> also be called in ->iomap_end(). But one COW operation may call
> ->iomap_apply() many times, and so does the end-io. Thus, I think it would
> be nice to move it to the bottom of ->dax_iomap_actor(), called just once in
> each COW operation.
I'm sorry but I don't follow what you suggest. One COW operation is a call
to dax_iomap_rw(), isn't it? That may call iomap_apply() several times,
each invocation calls ->iomap_begin(), ->actor() (dax_iomap_actor()),
->iomap_end() once. So I don't see a difference between doing something in
->actor() and ->iomap_end() (besides the passed arguments but that does not
seem to be your concern). So what do you exactly want to do?
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2019-05-28 9:17 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-29 17:26 [PATCH v4 00/18] btrfs dax support Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 01/18] btrfs: create a mount option for dax Goldwyn Rodrigues
2019-05-21 18:02 ` Darrick J. Wong
2019-04-29 17:26 ` [PATCH 02/18] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 03/18] btrfs: basic dax read Goldwyn Rodrigues
2019-05-21 15:14 ` Darrick J. Wong
2019-05-22 21:50 ` Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes Goldwyn Rodrigues
2019-05-21 16:51 ` Darrick J. Wong
2019-05-22 20:14 ` Goldwyn Rodrigues
2019-05-23 2:10 ` Dave Chinner
2019-05-23 9:05 ` Shiyang Ruan
2019-05-23 11:51 ` Goldwyn Rodrigues
2019-05-27 8:25 ` Shiyang Ruan
2019-05-28 9:17 ` Jan Kara [this message]
2019-05-29 2:01 ` Shiyang Ruan
2019-05-29 2:47 ` Dave Chinner
2019-05-29 4:02 ` Shiyang Ruan
2019-05-29 4:07 ` Darrick J. Wong
2019-05-29 4:46 ` Dave Chinner
2019-05-29 13:46 ` Jan Kara
2019-05-29 22:14 ` Dave Chinner
2019-05-30 11:16 ` Jan Kara
2019-05-30 22:59 ` Dave Chinner
2019-04-29 17:26 ` [PATCH 05/18] btrfs: return whether extent is nocow or not Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 06/18] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 07/18] btrfs: add dax write support Goldwyn Rodrigues
2019-05-21 17:08 ` Darrick J. Wong
2019-04-29 17:26 ` [PATCH 08/18] dax: memcpy page in case of IOMAP_DAX_COW for mmap faults Goldwyn Rodrigues
2019-05-21 17:46 ` Darrick J. Wong
2019-05-22 19:11 ` Goldwyn Rodrigues
2019-05-23 4:02 ` Darrick J. Wong
2019-05-23 12:10 ` Jan Kara
2019-04-29 17:26 ` [PATCH 09/18] btrfs: Add dax specific address_space_operations Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 10/18] dax: replace mmap entry in case of CoW Goldwyn Rodrigues
2019-05-21 17:35 ` Darrick J. Wong
2019-05-23 13:38 ` Jan Kara
2019-04-29 17:26 ` [PATCH 11/18] btrfs: add dax mmap support Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 12/18] btrfs: allow MAP_SYNC mmap Goldwyn Rodrigues
2019-05-10 15:32 ` [PATCH for-goldwyn] btrfs: disallow MAP_SYNC outside of DAX mounts Adam Borowski
2019-05-10 15:41 ` Dan Williams
2019-05-10 15:59 ` Pankaj Gupta
2019-05-23 13:44 ` [PATCH 12/18] btrfs: allow MAP_SYNC mmap Jan Kara
2019-05-23 16:19 ` Adam Borowski
2019-04-29 17:26 ` [PATCH 13/18] fs: dedup file range to use a compare function Goldwyn Rodrigues
2019-05-21 18:17 ` Darrick J. Wong
2019-04-29 17:26 ` [PATCH 14/18] dax: memcpy before zeroing range Goldwyn Rodrigues
2019-05-21 17:27 ` Darrick J. Wong
2019-04-29 17:26 ` [PATCH 15/18] btrfs: handle dax page zeroing Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 16/18] btrfs: Writeprotect mmap pages on snapshot Goldwyn Rodrigues
2019-05-23 14:04 ` Jan Kara
2019-05-23 15:27 ` Goldwyn Rodrigues
2019-05-23 19:07 ` Jan Kara
2019-05-23 21:22 ` Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 17/18] btrfs: Disable dax-based defrag and send Goldwyn Rodrigues
2019-04-29 17:26 ` [PATCH 18/18] btrfs: trace functions for btrfs_iomap_begin/end Goldwyn Rodrigues
-- strict thread matches above, loose matches on Subject: below --
2019-04-16 16:41 [PATCH v3 00/18] btrfs dax support Goldwyn Rodrigues
2019-04-16 16:41 ` [PATCH 04/18] dax: Introduce IOMAP_DAX_COW to CoW edges during writes Goldwyn Rodrigues
2019-04-17 16:46 ` Darrick J. Wong
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