Does the OS mount command, for a given partition, have smarts to wait for an active fsck, on that partition, to end "gracefully"?

Context:

  • Filesystem has been tagged by tune2fs for auto-trigger of fsck after mount-count "reboots".

  • External USB backup disk is plugged in, but /etc/fstab specifies "no auto-mount" and the mount point is non-standard, namely "/site", specifically to "mask" all such drives from the auto-mounting services.

Anybody know for sure if the fsck triggered by the boot process will

  • [1] allow the OS on the primary boot disk to proceed with the Desktop Manager, allowing a user session login, even if the fsck on the external drive is not finished,      

or

  • [2] even if no auto-mount for that attached external USB drive, the auto-triggered boot-time fsck on the USB will prevent the User from obtaining and performing a login?

If [1], if I enter a separate command to mount the USB-based partition,

  • does the OS handle the process "gracefully", allowing the fsck to finish before mounting, or

  • does it force fsck to abandon by interrupting it, or

  • does the fsck process "break", because the partition is now mounted and being "modified" during the fsck process.