linux-kernel - Re: [PATCH 0/9] add ext4 per-inode DAX flag

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Date:   Tue, 5 Sep 2017 21:12:35 -0500
From:   Eric Sandeen <esandeen@...hat.com>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Cc:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
        linux-ext4@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-xfs@...r.kernel.org
Subject: Re: [PATCH 0/9] add ext4 per-inode DAX flag

On 9/5/17 5:35 PM, Ross Zwisler wrote:
> The original intent of this series was to add a per-inode DAX flag to ext4
> so that it would be consistent with XFS.  In my travels I found and fixed
> several related issues in both ext4 and XFS.

Hi Ross -

hch had a lot of reasons to nuke the dax flag from orbit, and we just
/disabled/ it in xfs due to its habit of crashing the kernel...
so a couple questions:

1) does this series pass hch's "test the per-inode DAX flag" fstest?
2) do we have an agreement that we need this flag at all, or is this
   just a parity item because xfs has^whad a per-inode flag?

Thanks,
-Eric

> I'm not fully happy with the ways that ext4 DAX interacts with conflicting
> features (journaling, inline data and encryption).  My goal with this
> series was to make all these interactions as consistent as possilble, and
> of course to make them safe.  If anyone has ideas for improvements, I'm
> very open.
> 
> Ross Zwisler (9):
>   ext4: remove duplicate extended attributes defs
>   xfs: always use DAX if mount option is used
>   xfs: validate bdev support for DAX inode flag
>   ext4: add ext4_should_use_dax()
>   ext4: ext4_change_inode_journal_flag error handling
>   ext4: safely transition S_DAX on journaling changes
>   ext4: prevent data corruption with inline data + DAX
>   ext4: add sanity check for encryption + DAX
>   ext4: add per-inode DAX flag
> 
>  fs/ext4/ext4.h      | 47 ++++++---------------------------------------
>  fs/ext4/ext4_jbd2.h | 16 ++++++++++++++++
>  fs/ext4/inline.c    | 10 ----------
>  fs/ext4/inode.c     | 45 ++++++++++++++++++++++++-------------------
>  fs/ext4/ioctl.c     | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>  fs/ext4/super.c     |  8 ++++++++
>  fs/xfs/xfs_ioctl.c  | 14 +++++++++++---
>  7 files changed, 119 insertions(+), 76 deletions(-)
>