Hi, I am unmounting an ext4 filesystem (Ubuntu 16.04), fuser shows that no user-space processes are holding a handle to it: > root@kakhan-ubuntu:/# fuser -vm /oldroot > USER PID ACCESS COMMAND > /oldroot: root kernel mount /oldroot lsof gives this: > root@kakhan-ubuntu:/# lsof | grep sda > jbd2/sda1 368 root cwd DIR 0,20 340 2 / > jbd2/sda1 368 root rtd DIR 0,20 340 2 / > jbd2/sda1 368 root txt unknown /proc/368/exe If I look into /proc/../mounts I see lots of kernel specific processes which have /dev/sda1 listed in their mounts: > root@kakhan-ubuntu:/# find /proc -name mounts | xargs grep /dev/sda1 > /proc/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/1/task/1/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/1/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/2/task/2/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/2/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/3/task/3/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/3/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/5/task/5/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/5/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > /proc/7/task/7/mounts:/dev/sda1 /oldroot ext4 rw,relatime,errors=remount-ro,data=ordered 0 0 > # and whole bunch of others ...) I am unable to unmount the filesystem: > root@kakhan-ubuntu:/# umount /oldroot > umount: /oldroot: target is busy > (In some cases useful info about processes that > use the device is found by lsof(8) or fuser(1).) Can anyone please provide some pointers on how should I proceed with unmounting the filesystem? (Context: I copied binaries into a tmpfs and did a pivot_root to it, i.e., the opposite of what happens from initramfs during boot. I killed all the userspace processes holding a handle to the oldroot. This issue is different than the one I faced a couple of months ago during the same exercise on CentOS [1], where systemd-udevd needed a restart to release the handle to the old filesystem. In this case there's no userspace procs accessing the mountpoint.) [1] http://permalink.gmane.org/gmane.comp.file-systems.ext4/53314 -- Kamran. http://inspirated.com/ -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
