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

[Ross Zwisler]

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@xxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-and-Tested-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>

Re-tested this version of the series with some injected DAX errors, and it
looks good.