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From: David Sterba <dsterba@suse.cz>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: Re: [PATCH 01/15] btrfs: create a mount option for dax
Date: Thu, 28 Mar 2019 15:49:22 +0100	[thread overview]
Message-ID: <20190328144922.GL29086@twin.jikos.cz> (raw)
In-Reply-To: <20190326190301.32365-2-rgoldwyn@suse.de>

On Tue, Mar 26, 2019 at 02:02:47PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> This sets S_DAX in inode->i_flags, which can be used with
> IS_DAX().

I haven't followed the dax developments recently, IIRC the mount option
'dax' was meant to be a temporary solution. I don't know if this has
stuck, or is discouraged to be added to new code. The replacement is the
per-inode xflag.

> The dax option is restricted to non multi-device mounts.
> dax interacts with the device directly instead of using bio, so
> all bio-hooks which we use for multi-device cannot be performed
> here. While regular read/writes could be manipulated with
> RAID0/1, mmap() is still an issue.
> 
> Auto-setting free space tree, because dealing with free space
> inode (specifically readpages) is a nightmare.
> Auto-setting nodatasum because we don't get callback for writing
> checksums after mmap()s.

As discussed before, mandating free-space-tree for dax is ok and even
more that it does not complicate the space cache v1 code.

> Store the dax_device in fs_info which will be used in iomap code.
> Question: Since we have only one dax device, I thought fs_info is
> the best place. However, should it moved to btrfs_device?

At this point it's probably ok to store it in fs_info as the
multi-device support does not exist. If this changes, then the device is
the right place.

As Adam mentioned, support for the 'single' profile would be nice. It's
the simplest profile that over multiple devices only splits the logical
address space (of btrfs) into more chunks. However I don't know if the
dax side does require something that makes this impossible to coexist.

  parent reply	other threads:[~2019-03-28 14:48 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190326190301.32365-1-rgoldwyn@suse.de>
2019-03-26 19:02 ` [PATCH 01/15] btrfs: create a mount option for dax Goldwyn Rodrigues
2019-03-26 19:10   ` Matthew Wilcox
2019-03-27 11:00     ` Goldwyn Rodrigues
2019-03-27 12:00       ` Matthew Wilcox
2019-03-27 12:26         ` Goldwyn Rodrigues
2019-03-27 23:31         ` Goldwyn Rodrigues
2019-03-27 17:38     ` Adam Borowski
2019-03-28 14:49   ` David Sterba [this message]
2019-03-28 17:28   ` David Sterba
2019-03-28 17:57     ` Darrick J. Wong
2019-04-01 20:43     ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 02/15] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 03/15] btrfs: basic dax read Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 04/15] dax: Introduce IOMAP_F_COW for copy-on-write Goldwyn Rodrigues
2019-03-27 17:54   ` Darrick J. Wong
2019-03-27 18:58     ` Goldwyn Rodrigues
2019-03-28 14:45       ` Darrick J. Wong
2019-04-01  4:38   ` Dave Chinner
2019-04-01 21:41     ` Goldwyn Rodrigues
2019-04-01 23:06       ` Dave Chinner
2019-04-03  1:56         ` Goldwyn Rodrigues
2019-04-03  3:20           ` Dave Chinner
2019-04-07  7:26     ` Christoph Hellwig
2019-03-26 19:02 ` [PATCH 05/15] btrfs: return whether extent is nocow or not Goldwyn Rodrigues
2019-03-31 18:42   ` Nikolay Borisov
2019-03-26 19:02 ` [PATCH 06/15] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 07/15] btrfs: add dax write support Goldwyn Rodrigues
2019-03-28 14:53   ` Darrick J. Wong
2019-04-01 20:39     ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 08/15] dax: add dax_iomap_cow to copy a mmap page before writing Goldwyn Rodrigues
2019-03-28 15:41   ` Darrick J. Wong
2019-03-26 19:02 ` [PATCH 09/15] btrfs: add dax mmap support Goldwyn Rodrigues
2019-03-28 15:45   ` Darrick J. Wong
2019-03-26 19:02 ` [PATCH 10/15] btrfs: Add dax specific address_space_operations Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 11/15] fs: dedup file range to use a compare function Goldwyn Rodrigues
2019-03-28 17:04   ` Darrick J. Wong
2019-04-01 20:36     ` Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 12/15] btrfs: trace functions for btrfs_iomap_begin/end Goldwyn Rodrigues
2019-03-26 19:02 ` [PATCH 13/15] btrfs: handle dax page zeroing Goldwyn Rodrigues
2019-03-26 19:03 ` [PATCH 14/15] btrfs: Disable dax-based defrag and send Goldwyn Rodrigues
2019-03-26 19:03 ` [PATCH 15/15] btrfs: Writeprotect mmap pages on snapshot Goldwyn Rodrigues
2019-03-28 15:48   ` Darrick J. Wong
2019-03-26 19:09 ` [PATCH v2 00/15] btrfs dax support Goldwyn Rodrigues
2019-03-27 20:14   ` Adam Borowski
2019-03-27 23:26     ` Goldwyn Rodrigues
2019-03-28 10:24       ` [PATCH] btrfs: allow MAP_SYNC mmap Adam Borowski
2019-03-28 10:42         ` Adam Borowski
2019-04-01 20:08         ` Goldwyn Rodrigues

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