On Thu, Jul 19, 2018 at 05:06:42PM +0200, Jan Kara wrote:

Yeah. Actually previous version of the fix (not posted publicly) submitted
partial bio and then reused the bio to submit more. This is also the way
__blkdev_direct_IO operates. Martin optimized this to fill the bio
completely (as we know we have enough bvecs) before submitting which has
chances to perform better. I'm fine with either approach, just we have to
decide which way to go.

I think this first version is going to be less fragile, so I we should
aim for that.