Comment 4 for bug 1694596

I'm adding the actual errors I saw, just for the record.

What happens is that the root file system becomes read-only due to errors on the drive. My root file system is a logical volume on an encrypted partition (LVM with LUKS encryption), mounted and encrypted with the following options:

$ mount | grep ubuntu
/dev/mapper/ubuntu--vg-root on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)

$ sudo cryptsetup status nvme0n1p3_crypt
/dev/mapper/nvme0n1p3_crypt is active and is in use.
  type: LUKS1
  cipher: aes-xts-plain64
  keysize: 512 bits
  device: /dev/nvme0n1p3
  offset: 4096 sectors
  size: 498063360 sectors
  mode: read/write
  flags: discards

When the file system was re-mounted read-only due to errors, I booted Ubuntu 16.04.2 from a USB flash drive and ran "e2fsck" to repair the file system:

ubuntu@ubuntu:~$ sudo e2fsck -pfv /dev/mapper/ubuntu--vg-root
/dev/mapper/ubuntu--vg-root: recovering journal
/dev/mapper/ubuntu--vg-root: Inodes that were part of a corrupted orphan linked list found.

/dev/mapper/ubuntu--vg-root: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
        (i.e., without -a or -p options)

So then I ran the command again without the "-p" option, but with the "-y" option to answer "yes" to all questions, and the command fixed 329 errors:

ubuntu@ubuntu:~$ sudo e2fsck -fvy /dev/mapper/ubuntu--vg-root
e2fsck 1.42.13 (17-May-2015)
Pass 1: Checking inodes, blocks, and sizes
Inodes that were part of a corrupted orphan linked list found. Fix? yes

[ ... 327 errors not shown ...]

Free inodes count wrong (13486735, counted=13478898).
Fix? yes

/dev/mapper/ubuntu--vg-root: ***** FILE SYSTEM WAS MODIFIED *****

     1045518 inodes used (7.20%, out of 14524416)
        2413 non-contiguous files (0.2%)
         851 non-contiguous directories (0.1%)
             # of inodes with ind/dind/tind blocks: 27/27/27
             Extent depth histogram: 975523/235
    30224290 blocks used (52.03%, out of 58093568)
           0 bad blocks
           6 large files

      838712 regular files
      113346 directories
          67 character device files
          29 block device files
           3 fifos
          28 links
       93308 symbolic links (69609 fast symbolic links)
          44 sockets
------------
     1045537 files

This is the second day I'm running with the Ubuntu 16.04 GA Linux kernel version 4.4.0-78 (instead of the HWE Linux kernel), and it still seems to be okay, but the problem can take a few days to appear.