On Sat, Mar 19, 2016 at 06:20:24PM -0700, Linus Torvalds wrote: > On Mon, Mar 14, 2016 at 10:17 AM, Benjamin LaHaise <[email protected]> wrote: > > > > I had some time last week to make an aio openat do what it can in > > submit context. The results are an improvement: when openat is handled > > in submit context it completes in about half the time it takes compared > > to the round trip via the work queue, and it's not terribly much code > > either. > > This looks good to me, and I do suspect that any of these aio paths > should strive to have a synchronous vs threaded model. I think that > makes the whole thing much more interesting from a performance > standpoint.
Umm... You do realize that LOOKUP_RCU in flags does *NOT* guarantee that it won't block, right? At the very least one would need to refuse to fall back on non-RCU mode without a full restart. Furthermore, vfs_open() itself can easily block. So this new LOOKUP flag makes no sense, and it's in the just about _the_ worst place possible for adding special cases with ill-defined semantics - do_last() is already far too convoluted and needs untangling, not adding half-assed kludges.
