Re: [PATCH 3/6] io_uring: allow allocated fixed files for openat/openat2

[Jens Axboe <axboe@kernel.dk>]

On 5/12/22 11:28 PM, Hao Xu wrote:
> ? 2022/5/12 ??8:23, Jens Axboe ??:
>> On 5/12/22 2:21 AM, Hao Xu wrote:
>>> ? 2022/5/9 ??11:50, Jens Axboe ??:
>>>> If the application passes in IORING_FILE_INDEX_ALLOC as the file_slot,
>>>> then that's a hint to allocate a fixed file descriptor rather than have
>>>> one be passed in directly.
>>>>
>>>> This can be useful for having io_uring manage the direct descriptor space.
>>>>
>>>> Normal open direct requests will complete with 0 for success, and < 0
>>>> in case of error. If io_uring is asked to allocated the direct descriptor,
>>>> then the direct descriptor is returned in case of success.
>>>>
>>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>> ---
>>>>    fs/io_uring.c                 | 32 +++++++++++++++++++++++++++++---
>>>>    include/uapi/linux/io_uring.h |  9 +++++++++
>>>>    2 files changed, 38 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>>> index 8c40411a7e78..ef999d0e09de 100644
>>>> --- a/fs/io_uring.c
>>>> +++ b/fs/io_uring.c
>>>> @@ -4697,7 +4697,7 @@ static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>>        return __io_openat_prep(req, sqe);
>>>>    }
>>>>    -static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
>>>> +static int io_file_bitmap_get(struct io_ring_ctx *ctx)
>>>>    {
>>>>        struct io_file_table *table = &ctx->file_table;
>>>>        unsigned long nr = ctx->nr_user_files;
>>>> @@ -4722,6 +4722,32 @@ static int __maybe_unused io_file_bitmap_get(struct io_ring_ctx *ctx)
>>>>        return -ENFILE;
>>>>    }
>>>>    +static int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
>>>> +                   struct file *file, unsigned int file_slot)
>>>> +{
>>>> +    int alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;
>>>> +    struct io_ring_ctx *ctx = req->ctx;
>>>> +    int ret;
>>>> +
>>>> +    if (alloc_slot) {
>>>> +        io_ring_submit_lock(ctx, issue_flags);
>>>> +        file_slot = io_file_bitmap_get(ctx);
>>>> +        if (unlikely(file_slot < 0)) {
>>>> +            io_ring_submit_unlock(ctx, issue_flags);
>>>> +            return file_slot;
>>>> +        }
>>>> +    }
>>>
>>> if (alloc_slot) {
>>>   ...
>>> } else {
>>>          file_slot -= 1;
>>> }
>>>
>>> Otherwise there is off-by-one error.
>>>
>>> Others looks good,
>>>
>>> Reviewed-by: Hao Xu <howeyxu@tencent.com>
>>
>> Thanks, you are correct, I've folded that in.
>>
> 
> Hi Jens,
> I've rebased multishot accept based on your fixed-alloc branch:
> 
> https://github.com/HowHsu/linux/commits/for-5.19/io_uring_multishot_accept_v6
> 
> Let me know when ixed-alloc is ready, then I'll do the final rebase
> for multishot accept and send it to the list, including the liburing
> change.

Just base it against for-5.19/io_uring, I'm fixing the one-off and
pushing it out.

-- 
Jens Axboe