[PATCHSET v2 0/6] Allow allocated direct descriptors

[Jens Axboe <axboe@kernel.dk>]

Hi,

Currently using direct descriptors with open or accept requires the
application to manage the descriptor space, picking which slot to use
for any given file. However, there are cases where it's useful to just
get a direct descriptor and not care about which value it is, instead
just return it like a normal open or accept would.

This will also be useful for multishot accept support, where allocated
direct descriptors are a requirement to make that feature work with
these kinds of files.

This adds support for allocating a new fixed descriptor. This is chosen
by passing in IORING_FILE_INDEX_ALLOC as the fixed slot, which is beyond
any valid value for the file_index.

Can also be found here:

https://git.kernel.dk/cgit/linux-block/log/?h=for-5.19/io_uring-fixed-alloc

 fs/io_uring.c                 | 113 +++++++++++++++++++++++++++++++---
 include/uapi/linux/io_uring.h |  17 ++++-
 2 files changed, 120 insertions(+), 10 deletions(-)

v2:	- Fix unnecessary clear (Hao)
	- Add define for allocating a descriptor rather than use
	  UINT_MAX.
	- Add patch bumping max file table size to 1M (from 32K)
	- Add ability to register a sparse file table upfront rather
	  then have the application pass in a big array of -1.

-- 
Jens Axboe