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

[Hao Xu <haoxu.linux@gmail.com>]

在 2022/5/12 下午8:23, Jens Axboe 写道:
> 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.

Thanks,
Hao