On Thu, Jul 18, 2019 at 04:43:52PM -0700, Bjorn Andersson wrote: > On Thu 18 Jul 16:17 PDT 2019, Al Viro wrote: > > > On Thu, Jul 18, 2019 at 04:10:54PM -0700, Bjorn Andersson wrote: > > > Implement a wrapper for aio_read()/write() to allow async IO on files > > > not implementing the iter version of read/write, such as sysfs. This > > > mimics how readv/writev uses non-iter ops in do_loop_readv_writev(). > > > > IDGI. How would that IO manage to be async? And what's the point > > using aio in such situations in the first place? > > The point is that an application using aio to submit io operations on a > set of files, can use the same mechanism to read/write files that > happens to be implemented by driver only implementing read/write (not > read_iter/write_iter) in the registered file_operations struct, such as > kernfs. > > In this particular case I have a sysfs file that is accessing hardware > and hence will block for a while and using this patch I can io_submit() > a write and handle the completion of this in my normal event loop. > > > Each individual io operation will be just as synchronous as the current > iter-based mechanism - for the drivers that implement that. Just adding the fops is not enough. I have patches floating around at Solace that add thread based fallbacks for files that don't have an aio read / write implementation, but I'm not working on that code any more. The thread based methods were quite useful in applications that had a need for using other kernel infrastructure in their main event loops. -ben > Regards, > Bjorn > -- "Thought is the essence of where you are now."
