Re: [PATCH 1/2] selftests: ublk: don't keep the fault_inject timespec on the stack

[Ming Lei <tom.leiming@gmail.com>]

On Thu, Oct 08, 2026 at 10:45:39PM +0800, Qiliang Yuan wrote:
> The fault_inject target delays each I/O with an IORING_OP_TIMEOUT, and
> generic_06 relies on the delay to kill the server while an I/O is still
> outstanding.
> 
> The timespec of the timeout is a local variable of
> ublk_fault_inject_queue_io(). The SQE only records its address, and
> io_uring reads it when the SQE is submitted, after the function has
> returned. The timeout gets whatever the stack holds by then and expires
> almost at once, so --delay_us has no effect, and generic_06 fails
> because dd completes before the server is killed.
> 
> Store the timespec in the per-device fi_opts, and split the delay into
> seconds and nanoseconds so that delays of a second or more give a valid
> timespec.
> 
> fio 4k random reads for 10 s at queue depth 1 on a fault_inject device
> with --delay_us 1000000:
> 
>                   before      after   expected
>   I/Os            446927         10         10
>   mean latency   18.3 us    1.000 s        1 s
> 
> Fixes: 81586652bb1f ("selftests: ublk: add generic_06 for covering fault inject")
> Signed-off-by: Qiliang Yuan <odys.yuan@gmail.com>

Reviewed-by: Ming Lei <tom.leiming@gmail.com>

Thanks, 
Ming