From: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: "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: Mon, 27 May 2019 16:25:41 +0800 [thread overview]
Message-ID: <1620c513-4ce2-84b0-33dc-2675246183ea@cn.fujitsu.com> (raw)
In-Reply-To: <20190523115109.2o4txdjq2ft7fzzc@fiona>
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.
--
Thanks,
Shiyang Ruan.
>>
>> My RFC patchset[1] is implemented in this way and works for me, though it is
>> far away from perfectness.
>>
>> [1]: https://patchwork.kernel.org/cover/10904307/
>>
>
next prev parent reply other threads:[~2019-05-27 8:25 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 [this message]
2019-05-28 9:17 ` Jan Kara
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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