On 2/8/19 6:34 PM, Jens Axboe wrote:

We normally have to fget/fput for each IO we do on a file. Even with
the batching we do, the cost of the atomic inc/dec of the file usage
count adds up.

This adds IORING_REGISTER_FILES, and IORING_UNREGISTER_FILES opcodes
for the io_uring_register(2) system call. The arguments passed in must
be an array of __s32 holding file descriptors, and nr_args should hold
the number of file descriptors the application wishes to pin for the
duration of the io_uring instance (or until IORING_UNREGISTER_FILES is
called).

When used, the application must set IOSQE_FIXED_FILE in the sqe->flags
member. Then, instead of setting sqe->fd to the real fd, it sets sqe->fd
to the index in the array passed in to IORING_REGISTER_FILES.

Files are automatically unregistered when the io_uring instance is torn
down. An application need only unregister if it wishes to register a new
set of fds.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
  fs/io_uring.c                 | 256 ++++++++++++++++++++++++++++++----
  include/uapi/linux/io_uring.h |   9 +-
  2 files changed, 235 insertions(+), 30 deletions(-)

Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes


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