Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file table

On 8/17/21 3:33 AM, Pavel Begunkov wrote:

On 8/16/21 4:45 PM, Stefan Metzmacher wrote:

quoted

Hi Pavel,

quoted

The behaviour is controlled by setting sqe->file_index, where 0 implies
the old behaviour. If non-zero value is specified, then it will behave
as described and place the file into a fixed file slot
sqe->file_index - 1. A file table should be already created, the slot
should be valid and empty, otherwise the operation will fail.

Note 1: we can't use IOSQE_FIXED_FILE to switch between modes, because
accept takes a file, and it already uses the flag with a different
meaning.

Would it be hard to support IOSQE_FIXED_FILE for the dirfd of openat*, renameat, unlinkat, statx?
(And mkdirat, linkat, symlinkat when they arrive)
renameat and linkat might be trickier as they take two dirfds, but it
would make the feature more complete and useful.

Good idea. There is nothing blocking on the io_uring side, but
the fs part may get ugly, e.g. too intrusive. We definitely need
to take a look

Indeed, the io_uring side is trivial, but the VFS interface would
require a lot of man handling... That's why I didn't add support for
fixed files originally.

-- 
Jens Axboe