On Thu, Sep 09, 2021 at 09:30:03PM -0600, Jens Axboe wrote: > > Again, we should never, ever modify the iovec (or bvec, etc.) array in > > ->read_iter()/->write_iter()/->sendmsg()/etc. instances. If you see > > such behaviour anywhere, report it immediately. Any such is a blatant > > bug. > > Yes that was wrong, the iovec is obviously const. But that really > doesn't change the original point, which was that copying the iov_iter > itself unconditionally would be miserable. Might very well be true, but... won't your patch hit the reimport on every short read? And the cost of uaccess in there is *much* higher than copying of 48 bytes into local variable... Or am I misreading your patch? Note that short reads on reaching EOF are obviously normal - it's not a rare case at all.
