Re: [PATCH 1/2] ublk: reset per-IO canceled flag on each fetch

[Ming Lei]

On Fri, Apr 03, 2026 at 09:23:55PM -0600, Uday Shankar wrote:
> If a ublk server starts recovering devices but dies before issuing fetch
> commands for all IOs, cancellation of the fetch commands that were
> successfully issued may never complete. This is because the per-IO
> canceled flag can remain set even after the fetch for that IO has been
> submitted - the per-IO canceled flags for all IOs in a queue are reset
> together only once all IOs for that queue have been fetched. So if a
> nonempty proper subset of the IOs for a queue are fetched when the ublk
> server dies, the IOs in that subset will never successfully be canceled,
> as their canceled flags remain set, and this prevents ublk_cancel_cmd
> from actually calling io_uring_cmd_done on the commands, despite the
> fact that they are outstanding.
> 
> Fix this by resetting the per-IO cancel flags immediately when each IO
> is fetched instead of waiting for all IOs for the queue (which may never
> happen).
> 
> Signed-off-by: Uday Shankar <ushankar@xxxxxxxxxxxxxxx>

Fixes: 728cbac5fe21 ("ublk: move device reset into ublk_ch_release()")

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


thanks,
Ming