linux-ext4 - Re: [PATCH v5 08/17] dax: set errors in mapping when writeback fails

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Date:   Mon, 05 Jun 2017 21:08:26 -0400
From:   Jeff Layton <jlayton@...hat.com>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
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,
        corbet@....net, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 08/17] dax: set errors in mapping when writeback fails

On Mon, 2017-06-05 at 19:01 -0600, Ross Zwisler wrote:
> On Wed, May 31, 2017 at 08:45:31AM -0400, Jeff Layton wrote:
> > Jan's description for this patch is much better than mine, so I'm
> > quoting it verbatim here:
> > 
> > -----------------8<-----------------
> > DAX currently doesn't set errors in the mapping when cache flushing
> > fails in dax_writeback_mapping_range(). Since this function can get
> > called only from fsync(2) or sync(2), this is actually as good as it can
> > currently get since we correctly propagate the error up from
> > dax_writeback_mapping_range() to filemap_fdatawrite()
> > 
> > However, in the future better writeback error handling will enable us to
> > properly report these errors on fsync(2) even if there are multiple file
> > descriptors open against the file or if sync(2) gets called before
> > fsync(2). So convert DAX to using standard error reporting through the
> > mapping.
> > -----------------8<-----------------
> > 
> > For now, only do this when the FS_WB_ERRSEQ flag is set. The
> > AS_EIO/AS_ENOSPC flags are not currently cleared in the older code when
> > writeback initiation fails, only when we discover an error after waiting
> > on writeback to complete, so we only want to do this with errseq_t based
> > error handling to prevent seeing duplicate errors on fsync.
> > 
> > Signed-off-by: Jeff Layton <jlayton@...hat.com>
> > Reviewed-by: Jan Kara <jack@...e.cz>
> > Reviewed-by: Christoph Hellwig <hch@....de>
> > Reviewed-and-Tested-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> 
> Re-tested this version of the series with some injected DAX errors, and it
> looks good.

Excellent! Thanks very much for helping test it.

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