Re: [PATCH v4 5/7] fs: prioritize and separate direct_io from dax_io

From: Boaz Harrosh
Date: Mon May 02 2016 - 14:33:06 EST

On 05/02/2016 09:10 PM, Dan Williams wrote:
> The semantic I am talking about preserving is:
> buffered / unaligned write of a bad sector => -EIO on reading into the
> page cache

What about aligned buffered write? like write 0-to-eof
This still broken? (and is what restore apps do)

> ...and that the only guaranteed way to clear an error (assuming the
> block device supports it) is an O_DIRECT write.

Sure fixing dax_do_io will guaranty that.

> I still think we're talking past each other on this point.

Yes we are!

> This patch
> set is not overloading error semantics, it's fixing the error handling
> problem that was introduced in this commit:
> d475c6346a38 dax,ext2: replace XIP read and write with DAX I/O
> ...where we started overloading O_DIRECT and dax_do_io() semantics.

But above does not fix them does it? it just completely NULLs DAX for
O_DIRECT which is a great pity, why did we do all this work in the first

And then it keeps broken the aligned buffered writes, which are still
broken after this set.

I have by now read the v2 patches. And I think you guys did not yet try
the proper fix for dax_do_io. I think you need to go deeper into the loops
and selectively call bdev_* when error on a specific page copy. No need to
go through direct_IO path at all.
Do you need that I send you a patch to demonstrate what I mean?

But yes I feel too that "we're talking past each other". I did want
to come to LSF and talk to you, but was not invited. Should I call you?