On Sat, 2017-06-24 at 04:59 -0700, Christoph Hellwig wrote:

On Tue, Jun 20, 2017 at 01:44:44PM -0400, Jeff Layton wrote:

quoted

In order to query for errors with errseq_t, you need a previously-
sampled point from which to check. When you call
filemap_write_and_wait_range though you don't have a struct file and so
no previously-sampled value.

So can we simply introduce variants of them that take a struct file?
That would be:

 a) less churn
 b) less code
 c) less chance to get data integrity wrong

Yeah, I had that thought after I sent the reply to you earlier.

The main reason I didn't do that before was that I had myself convinced
that we needed to do the check_and_advance as late as possible in the
fsync process, after the metadata had been written.

Now that I think about it more, I think you're probably correct. As long
as we do the check and advance at some point after doing the
write_and_wait, we're fine here and shouldn't violate exactly once
semantics on the fsync return.
-- 
Jeff Layton [off-list ref]

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