On Tue, Jul 21, 2020 at 05:42:40PM +0200, Christoph Hellwig wrote:

On Tue, Jul 21, 2020 at 04:31:36PM +0100, Matthew Wilcox wrote:

quoted

quoted

Umm, no.  -ENOTBLK is internal - the file systems will retry using
buffered I/O and the error shall never escape to userspace (or even the
VFS for that matter).

Ah, I made the mistake of believing the comments that I could see in
your patch instead of reading the code.

Can I suggest deleting this comment:

        /*
         * No fallback to buffered IO on errors for XFS, direct IO will either
         * complete fully or fail.
         */

and rewording this one:

                /*
                 * Allow a directio write to fall back to a buffered
                 * write *only* in the case that we're doing a reflink
                 * CoW.  In all other directio scenarios we do not
                 * allow an operation to fall back to buffered mode.
                 */

as part of your revised patchset?

That isn't actually true.  In current mainline we only fallback on
reflink RMW cases, but with this series we also fall back for
invalidation failures.

... that's why I'm suggesting that you delete the first one and rewrite
the second one.  Because they aren't true.