What commit do you refer here to? From googling the hash I guess it is some kind of a kernel patch, but maybe you can clarify a little?
I just searched the kernel git source - so this git commit was accepted into kernel source in 2014. A quick look at diff it refers to a file in drivers/block/nvme-core.c which no longer exists. Looks like code was moved and plenty of changes. I find in drivers/nvme that : host/core.c:static unsigned char shutdown_timeout = 5; host/core.c:MODULE_PARM_DESC(shutdown_timeout, "timeout in seconds for controller shutdown"); which suggests the current default is 5 seconds to wait for h/w to ack - maybe some h/w needs more than 5 secs ... As I said, not an expert, but I'm definitely curious but not concerned. I have no actual evidence of cache flushes not being on disk. Not saying there are none - just I've not been aware of any. About all I know at this point :) gene