I'm trying to understand the difference in jbd2 behavior across Ubuntu 14.04 and Centos 7.1. Will appreciate any help. The uber goal is to resize the root filesystem without a reboot. Basically, all the necessary files are copied to a tmpfs, a pivot_root is performed then the old root is unmounted. On Ubuntu 14.04, after the old processes are killed I verify that no processes are holding handles to oldroot. > root@kakhan-ubuntu:~# fuser -vm /oldroot > USER PID ACCESS COMMAND > /oldroot: root kernel mount /oldroot jbd2 is still running: > root@kakhan-ubuntu:~# lsof | grep sda1 > jbd2/sda1 176 root cwd DIR 0,19 340 2 / > jbd2/sda1 176 root rtd DIR 0,19 340 2 / > jbd2/sda1 176 root txt unknown /proc/176/exe > root@kakhan-ubuntu:~# ps -f -p 176 > UID PID PPID C STIME TTY TIME CMD > root 176 2 0 17:19 ? 00:00:00 [jbd2/sda1-8] I can unmount the filesystem and do an fsck: > root@kakhan-ubuntu:~# umount /oldroot > root@kakhan-ubuntu:~# e2fsck -yf /dev/sda1 > ... > /dev/sda1: 64967/1831424 files (0.1% non-contiguous), 480018/7323904 blocks jbd2 does *not* hold a handle to the now unmounted filesystem: > root@kakhan-ubuntu:~# lsof | grep sda1 > root@kakhan-ubuntu:~# All good. On CentOS 7.1, I verify that no processed are holding handle to oldroot. > [root@kakhan-centos ~]# fuser -vm /oldroot > USER PID ACCESS COMMAND > /oldroot: root kernel mount /oldroot I can successfully unmount the filesystem but can't fsck it: > [root@kakhan-centos ~]# umount /oldroot > [root@kakhan-centos ~]# e2fsck -yf /dev/sda1 > e2fsck 1.42.9 (28-Dec-2013) > /dev/sda1 is in use. > e2fsck: Cannot continue, aborting. /dev/sda1 does not appear in /proc/mounts. Looks like jbd2 is the only thing that looks like it still cares about sda1: > [root@kakhan-centos ~]# lsof | grep sda1 > jbd2/sda1 394 root cwd DIR 0,14 340 22591 / > jbd2/sda1 394 root rtd DIR 0,14 340 22591 / > jbd2/sda1 394 root txt unknown /proc/394/exe > [root@kakhan-centos ~]# ps -f -p 394 > UID PID PPID C STIME TTY TIME CMD > root 394 2 0 00:15 ? 00:00:00 [jbd2/sda1-8] What I'm confused about is, why is the behavior different even though journaling is _enabled_ in *both* cases? On Ubuntu: > root@kakhan-ubuntu:~# dumpe2fs /dev/sda1 | grep features > dumpe2fs 1.42.9 (4-Feb-2014) > Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize > Journal features: journal_incompat_revoke On CentOS: > [root@kakhan-centos ~]# dumpe2fs /dev/sda1 | grep features > dumpe2fs 1.42.9 (28-Dec-2013) > Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize > Journal features: journal_incompat_revoke journal_64bit Any ideas? Thanks, -- 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
