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From: Adam Borowski <kilobyte@angband.pl>
To: Nikolay Borisov <nborisov@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 01/10] btrfs: create a mount option for dax
Date: Wed, 5 Dec 2018 15:59:05 +0100	[thread overview]
Message-ID: <20181205145905.xgwjyomiak6r22rs@angband.pl> (raw)
In-Reply-To: <4bf87dcb-dbac-c7ab-800c-98e10157f569@suse.com>

On Wed, Dec 05, 2018 at 02:43:03PM +0200, Nikolay Borisov wrote:
> One question below though .
> 
> > +++ b/fs/btrfs/super.c
> > @@ -739,6 +741,17 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
> >  		case Opt_user_subvol_rm_allowed:
> >  			btrfs_set_opt(info->mount_opt, USER_SUBVOL_RM_ALLOWED);
> >  			break;
> > +#ifdef CONFIG_FS_DAX
> > +		case Opt_dax:
> > +			if (btrfs_super_num_devices(info->super_copy) > 1) {
> > +				btrfs_info(info,
> > +					   "dax not supported for multi-device btrfs partition\n");
> 
> What prevents supporting dax for multiple devices so long as all devices
> are dax?

As I mentioned in a separate mail, most profiles are either redundant
(RAID0), require hardware support (RAID1, DUP) or are impossible (RAID5,
RAID6).

But, "single" profile multi-device would be useful and actually provide
something other dax-supporting filesystems don't have: combining multiple
devices into one logical piece.

On the other hand, DUP profiles need to be banned.  In particular, the
filesystem you mount might have existing DUP block groups.


Meow!
-- 
⢀⣴⠾⠻⢶⣦⠀ 
⣾⠁⢠⠒⠀⣿⡁ Ivan was a worldly man: born in St. Petersburg, raised in
⢿⡄⠘⠷⠚⠋⠀ Petrograd, lived most of his life in Leningrad, then returned
⠈⠳⣄⠀⠀⠀⠀ to the city of his birth to die.

  reply	other threads:[~2018-12-05 14:59 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-05 12:28 [PATCH 00/10] btrfs: Support for DAX devices Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 01/10] btrfs: create a mount option for dax Goldwyn Rodrigues
2018-12-05 12:42   ` Johannes Thumshirn
2018-12-05 12:43   ` Nikolay Borisov
2018-12-05 14:59     ` Adam Borowski [this message]
2018-12-05 12:28 ` [PATCH 02/10] btrfs: basic dax read Goldwyn Rodrigues
2018-12-05 13:11   ` Nikolay Borisov
2018-12-05 13:22   ` Johannes Thumshirn
2018-12-05 12:28 ` [PATCH 03/10] btrfs: dax: read zeros from holes Goldwyn Rodrigues
2018-12-05 13:26   ` Nikolay Borisov
2018-12-05 12:28 ` [PATCH 04/10] Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2018-12-05 13:35   ` Nikolay Borisov
2018-12-05 12:28 ` [PATCH 05/10] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 06/10] btrfs: dax write support Goldwyn Rodrigues
2018-12-05 13:56   ` Johannes Thumshirn
2018-12-05 12:28 ` [PATCH 07/10] dax: export functions for use with btrfs Goldwyn Rodrigues
2018-12-05 13:59   ` Johannes Thumshirn
2018-12-05 14:52   ` Christoph Hellwig
2018-12-06 11:46     ` Goldwyn Rodrigues
2018-12-12  8:07       ` Christoph Hellwig
2019-03-26 19:36   ` Dan Williams
2019-03-27 11:10     ` Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 08/10] btrfs: dax add read mmap path Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 09/10] btrfs: dax support for cow_page/mmap_private and shared Goldwyn Rodrigues
2018-12-05 12:28 ` [PATCH 10/10] btrfs: dax mmap write Goldwyn Rodrigues
2018-12-05 13:03 ` [PATCH 00/10] btrfs: Support for DAX devices Qu Wenruo
2018-12-05 21:36   ` Jeff Mahoney
2018-12-05 13:57 ` Adam Borowski
2018-12-05 21:37 ` Jeff Mahoney
2018-12-06  7:40   ` Robert White
2018-12-06 10:07 ` Johannes Thumshirn
2018-12-06 11:47   ` Goldwyn Rodrigues

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