Re: [PATCH v2 1/4] blk-flush: flush_rq should inherit first_rq's cmd_flags

[Christoph Hellwig]

On Mon, Jul 31, 2023 at 10:02:39PM +0800, Chengming Zhou wrote:
> The commit 84fca1b0c461 ("block: pass failfast and driver-specific flags to
> flush requests") says:
> If flush requests are being sent to the device we need to inherit the
> failfast and driver-specific flags, too, otherwise I/O will fail.
> 
> 1) REQ_FAILFAST_MASK: agree, shouldn't set to the flush_rq I think?
> 2) REQ_DRV: I don't get why this flag not set would cause I/O fail?

I don't think it would fail I/O by it's own, but it will cause the
nvme driver to not do the correct handling of an error when a flush
is set to multipath setups.