Where there's visible drive activity – for example, the flashing light of a USB flash drive or mobile hard disk drive – for some time after completion of a
Originally, I wondered whether post-
Where VFS_UNMOUNT(9) <https://www.freebsd.org/cgi/man.cgi?query=VFS_UNMOUNT&sektion=9&manpath=FreeBSD+13.0-RELEASE> lacks detail, <https://cgit.freebsd.org/src/commit/?id=bbb1e07d65242f6aaab7941c1e61a676eaec37b4> (2020-01-15) is helpful:
So, if I understand correctly, flushing can not be the explanation.
umount ⋯
command: - what are likely explanations for the activity?
Originally, I wondered whether post-
umount
activity is sometimes completion of pending disk writes (a flush).Where VFS_UNMOUNT(9) <https://www.freebsd.org/cgi/man.cgi?query=VFS_UNMOUNT&sektion=9&manpath=FreeBSD+13.0-RELEASE> lacks detail, <https://cgit.freebsd.org/src/commit/?id=bbb1e07d65242f6aaab7941c1e61a676eaec37b4> (2020-01-15) is helpful:
… Unlike VFS_SYNC(), the VFS_UNMOUNT() routine can suspend all processes when they request to do a write thus having a finite number of dirty buffers to write that cannot be expanded. There is no need to call VFS_SYNC() before calling VFS_UNMOUNT(), because VFS_UNMOUNT() needs to flush everything again anyway after suspending writes, to catch anything that was dirtied between the VFS_SYNC() and writes being suspended. …
So, if I understand correctly, flushing can not be the explanation.