linux-ext4 - Re: [PATCH 0/3] ext2, ext4, xfs: hard fail dax mount on unsupported devices

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Message-ID: <20181011103636.GC9467@quack2.suse.cz>
Date:   Thu, 11 Oct 2018 12:36:36 +0200
From:   Jan Kara <jack@...e.cz>
To:     Eric Sandeen <sandeen@...deen.net>
Cc:     linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        Ross Zwisler <zwisler@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 0/3] ext2, ext4, xfs: hard fail dax mount on unsupported
 devices

On Mon 08-10-18 14:32:46, Eric Sandeen wrote:
> In response to an earlier xfs patch to change how xfs reacts to
> dax incompatibilities, Dave said:
> 
> > I suspect we need to be more harsh are rejecting mounts with -o dax
> > on devices DAX isn't supported on. This mount option is going into
> > production systems - it's not just for "testing" as the comments all
> > claim. i Things will break in production systems if DAX isn't
> > enabled and they are expecting it to be enabled.
> 
> and I tend to agree, so proposing this change to hard-fail a dax mount if
> the device doesn't support it, instead of silently disabling the
> functionality.  Proposing for ext2, ext4, and xfs to keep behavior in
> sync.

Let me include Dan and Ross into the discussion since they were the ones
proposing the "silent fallback" behavior (ext4 actually did fail the mount
instead not so long ago - see 24f3478d664b "ext4: auto disable dax instead
of failing mount" from December). Guys, why did you choose the fallback
path instead of a failure?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR