1. Check the processes that are accessing the mount point.
2. Request the process/application owner to stop the processes that are accessing the mount point.
3. Try to un-mount the filesystem (without any option).
4. Mount the file-system back on its mount point.
5. If Step 4 didn't work, run a fsck on the un-mounted file-system (without any option).Otherwise continue Step 6.
6. Verify the mounted file-system is in Read-Write mode.
i) Check the processes again that are accessing the mount point and ask the Application owner to confirm that the stopped the services properly and ask them to kill any hung sessions.
ii) Try to unmount again without any option.
iii) If it still didn’t work, use lazy option “umount -l” (if this works, continue from Step 4).
iv) If lazy option didn’t work, we are in a chaotic situation. Try Forced un-mount by using “umount -f” & continue from Step 4.
v) After the above step, incase you couldn’t mount the file-system back, the best choice would be to go for a System reboot. (I’m not sure in this situation, forced Mount using ‘mount -f’ will work).
PS: Please note this procedure will not be applicable for OS file-systems such as /, /var, /opt etc. In that case, a system reboot would be the only solution, if the remount doesn't work.