On 5/28/22 3:45 AM, Xiaoguang Wang wrote:
> hi Hao,
>
>> Hi Xiaoguang,
>>
>> On 5/26/22 20:38, Xiaoguang Wang wrote:
>>> One big issue with file registration feature is that it needs user
>>> space apps to maintain free slot info about io_uring's fixed file
>>> table, which really is a burden for development. Now since io_uring
>>> starts to choose free file slot for user space apps by using
>>> IORING_FILE_INDEX_ALLOC flag in accept or open operations, but they
>>> need app to uses direct accept or direct open, which as far as I know,
>>> some apps are not prepared to use direct accept or open yet.
>>>
>>> To support apps, who still need real fds, use registration feature
>>> easier, let IORING_OP_FILES_UPDATE support to choose fixed file slot,
>>> which will return free file slot in cqe->res.
>>>
>>> TODO list:
>>> Need to prepare liburing corresponding helpers.
>>>
>>> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx>
>>> ---
>>> fs/io_uring.c | 50 ++++++++++++++++++++++++++++++++++---------
>>> include/uapi/linux/io_uring.h | 1 +
>>> 2 files changed, 41 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>> index 9f1c682d7caf..d77e6bbec81c 100644
>>> --- a/fs/io_uring.c
>>> +++ b/fs/io_uring.c
>>> @@ -680,6 +680,7 @@ struct io_rsrc_update {
>>> u64 arg;
>>> u32 nr_args;
>>> u32 offset;
>>> + u32 flags;
>>> };
>>> struct io_fadvise {
>>> @@ -7970,14 +7971,23 @@ static int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags)
>>> return 0;
>>> }
>>> +#define IORING_FILES_UPDATE_INDEX_ALLOC 1
>>> +
>>> static int io_rsrc_update_prep(struct io_kiocb *req,
>>> const struct io_uring_sqe *sqe)
>>> {
>>> + u32 flags = READ_ONCE(sqe->files_update_flags);
>>> +
>>> if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
>>> return -EINVAL;
>>> - if (sqe->rw_flags || sqe->splice_fd_in)
>>> + if (sqe->splice_fd_in)
>>> + return -EINVAL;
>>> + if (flags & ~IORING_FILES_UPDATE_INDEX_ALLOC)
>>> + return -EINVAL;
>>> + if ((flags & IORING_FILES_UPDATE_INDEX_ALLOC) && READ_ONCE(sqe->len) != 1)
>>
>> How about allowing multiple fd update in IORING_FILES_UPDATE_INDEX_ALLOC
>> case? For example, using the sqe->addr(the fd array) to store the slots we allocated, and let cqe return the number of slots allocated.
> Good idea, I'll try in patch v2, thanks.
> Jens, any comments about this patch? At least It's really helpful to our
> internal apps based on io_uring :)
I like this suggestion too, other thoughts in reply to the original.
--
Jens Axboe
