On 7/9/20 8:00 AM, Christoph Hellwig wrote: > On Thu, Jul 09, 2020 at 07:58:04AM -0600, Jens Axboe wrote: >>> We don't actually need any new field at all. By the time the write >>> returned ki_pos contains the offset after the write, and the res >>> argument to ->ki_complete contains the amount of bytes written, which >>> allow us to trivially derive the starting position. >> >> Then let's just do that instead of jumping through hoops either >> justifying growing io_rw/io_kiocb or turning kiocb into a global >> completion thing. > > Unfortunately that is a totally separate issue - the in-kernel offset > can be trivially calculated. But we still need to figure out a way to > pass it on to userspace. The current patchset does that by abusing > the flags, which doesn't really work as the flags are way too small. > So we somewhere need to have an address to do the put_user to. Right, we're just trading the 'append_offset' for a 'copy_offset_here' pointer, which are stored in the same spot... -- Jens Axboe
