Huh? Are you thinking dpkg is sending NVMe commands itself or something? No, that's not what that manpage means. dpkg is asking the kernel to write stuff to the page cache, and then asking for a guarantee that the data will continue to exist on next boot. The second half is what fsync does. Without fsync returning success, this is not guaranteed at all. And if you don't understand the point of the guarantee after reading my previous comment...and this is your way of saying so...further conversation will be pointless...
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Writing to disk is none of your business unless you are the kernel itself.
Huh? Are you thinking dpkg is sending NVMe commands itself or something? No, that's not what that manpage means. dpkg is asking the kernel to write stuff to the page cache, and then asking for a guarantee that the data will continue to exist on next boot. The second half is what fsync does. Without fsync returning success, this is not guaranteed at all. And if you don't understand the point of the guarantee after reading my previous comment...and this is your way of saying so...further conversation will be pointless...