Re: [PATCH] ublk: remove io_cmds list in ublk_queue

[Ming Lei <ming.lei@redhat.com>]

On Tue, Mar 18, 2025 at 12:14:17PM -0600, Uday Shankar wrote:
> The current I/O dispatch mechanism - queueing I/O by adding it to the
> io_cmds list (and poking task_work as needed), then dispatching it in
> ublk server task context by reversing io_cmds and completing the
> io_uring command associated to each one - was introduced by commit
> 7d4a93176e014 ("ublk_drv: don't forward io commands in reserve order")
> to ensure that the ublk server received I/O in the same order that the
> block layer submitted it to ublk_drv. This mechanism was only needed for
> the "raw" task_work submission mechanism, since the io_uring task work
> wrapper maintains FIFO ordering (using quite a similar mechanism in
> fact). The "raw" task_work submission mechanism is no longer supported
> in ublk_drv as of commit 29dc5d06613f2 ("ublk: kill queuing request by
> task_work_add"), so the explicit llist/reversal is no longer needed - it
> just duplicates logic already present in the underlying io_uring APIs.
> Remove it.
> 
> Signed-off-by: Uday Shankar <ushankar@purestorage.com>

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming