I wanted this to debug a NVMeoF error I saw in testing, but the error didn't reproduce after this. However, on my test machine, the NVMe drive it uses for its main storage doesn't implement support for flush, so I get an error in dmesg on every reboot and this is the output from that with these two patches applied:

nvme0: FLUSH sqid:1 cid:127 nsid:1
nvme0: INVALID OPCODE (00/01) crd:0 m:0 dnr:0 p:1 sqid:1 cid:127 cdw0:0
(nda0:nvme0:0:0:1): FLUSH. NCB: opc=0 fuse=0 nsid=1 prp1=0 prp2=0 cdw=0 0 0 0 0 0
(nda0:nvme0:0:0:1): CAM status: NVME Status Error
(nda0:nvme0:0:0:1): NVMe status: INVALID_OPCODE
(nda0:nvme0:0:0:1): Error 5, Retries exhausted
(nda0:nvme0:0:0:1): Synchronize cache failed

In D50632#1155884, @imp wrote:

I have some similar changes to do this for devd as well...

Are you good with the earlier change as well (D50631)?

In D50632#1155908, @jhb wrote:

In D50632#1155884, @imp wrote:

I have some similar changes to do this for devd as well...

Are you good with the earlier change as well (D50631)?

Yea. I am. There's no conflicts or other reasons I can think to stop this.. with the proviso we'll likely refactor this and its companion un the fututre