Re: [PATCHSET 0/4] Allow allocated direct descriptors

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

在 2022/5/9 上午7:49, Jens Axboe 写道:
> 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 UINT_MAX as the fixed slot, which otherwise has a limit
> of INT_MAX like any file descriptor does.
> 
>   fs/io_uring.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++---
>    1 file changed, 94 insertions(+), 6 deletions(-)
> 
Hi Jens,
I've read this idea of leveraging bitmap, it looks great. a small flaw
of it is that when the file_table is very long, the bitmap searching
seems to be O({length of table}/BITS_PER_LONG), to make the time
complexity stable, I did a linked list version, could you have a look
when you're avalible. totally untested, just to show my idea. Basically
I use a list to link all the free slots, when we need a slot, just get
the head of it.
https://github.com/HowHsu/linux/commits/for-5.19/io_uring_multishot_accept_v5

(borrowed some commit message from your patches)

Thanks,
Hao