linux-ext4 - Re: [PATCH v6 12/20] fs: add a new fstype flag to indicate how writeback errors are tracked

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Message-ID: <1497523332.4556.1.camel@redhat.com>
Date:   Thu, 15 Jun 2017 06:42:12 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...IV.linux.org.uk>, Jan Kara <jack@...e.cz>,
        tytso@....edu, axboe@...nel.dk, mawilcox@...rosoft.com,
        ross.zwisler@...ux.intel.com, corbet@....net,
        Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH v6 12/20] fs: add a new fstype flag to indicate how
 writeback errors are tracked

On Thu, 2017-06-15 at 01:22 -0700, Christoph Hellwig wrote:
> On Wed, Jun 14, 2017 at 01:24:43PM -0400, Jeff Layton wrote:
> > In this smaller set, it's only really used for DAX.
> 
> DAX only is implemented by three filesystems, please just fix them
> up in one go.
> 

Ok.

> > sync_file_range: ->fsync isn't called directly there, and I think we
> > probably want similar semantics to fsync() for it
> 
> sync_file_range is only supposed to sync data, so it should not call
> ->fsync.
> 

Correct.

But if there is a data writeback error, should we report an error on all
open fds at that time (like we will for fsync)?

I think we probably do want to do that, but like you say...there is no
file op for sync_file_range. It'll need some way to figure out what sort
of error tracking is in play.

> > JBD2: will try to re-set the error after clearing it with
> > filemap_fdatawait. That's problematic with the new infrastructure so we
> > need some way to avoid it.
> 
> JBD2 only has two users, please fix them up in one go.

I came up with a fix yesterday that makes the flag unnecessary there.

Thanks,
-- 
Jeff Layton <jlayton@...hat.com>