IO_uring Has Many Improvements Set To Go Into Linux 5.9

In addition to the many outlined changes expected for Linux 5.9, here's another big one: lots of IO_uring work for enhancing this modern Linux I/O interface.

Facebook's Jens Axboe who oversees the Linux storage/block code and leads the IO_uring efforts summed up the changes for Linux 5.9 as "hardening the code and/or making it easier to read and fixing [bits]." There is though a big change and that is proper async buffered reads support. That work was previously covered but didn't end up getting pulled into Linux 5.8 due to a branching difference but is now ready to go with Linux 5.9. The async buffered reads support for IO_uring has some nice performance advantages and lower CPU usage while also working its way off KThreads for the fast code path once the async buffered write support is in place.

Other IO_uring changes for Linux 5.9 also has cleaned up memory accounting in some areas, I/O completion optimizations, support for EPOLLEXCLUSIVE with IO_uring, and a variety of other fixes and minor improvements. More details via the IO_uring pull request sent out just minutes after the Linux 5.8 stable release.