On 8/29/20 9:32 PM, Shuveb Hussain wrote: > Jens, > > I'm coming up the the man page for io_uring(7) and I noticed that the > existing man page or other available documentation does not make it > clear about offset (off in the SQE) being a mandatory parameter for > the following operations: > IORING_OP_READ > IORING_OP_WRITE > IORING_OP_READV > IORING_OP_WRITEV > > Regular UNIX developers will expect subsequent read/write operations > on the same file descriptor to remember the file offset for files that > continue to be open. Is this the intended behavior or is it just that > it is not documented? If it is the latter, I'll clearly call it out in > the documentation. This is intended behavior, you should consider the READV to be just like preadv2() in that it takes the offset/iov/flags, and ditto on the write side. READ is basically what a pread2 would be, if it existed. That said, you can use off == -1 if IORING_FEAT_RW_CUR_POS is set in the feature flags upon ring creation, and that'll use (and updated) the current file offset. This works for any non-stream/pipe file type. -- Jens Axboe
