On Thu, Mar 09, 2017 at 02:15:01PM -0600, Eric Sandeen wrote:
> There are dueling comments in the xfs code about intent
> for log writes when unmounting a readonly filesystem.
>
> In xfs_mountfs, we see the intent:
>
> /*
> * Now the log is fully replayed, we can transition to full read-only
> * mode for read-only mounts. This will sync all the metadata and clean
> * the log so that the recovery we just performed does not have to be
> * replayed again on the next mount.
> */
>
> and it calls xfs_quiesce_attr(), but by the time we get to
> xfs_log_unmount_write(), it returns early for a RDONLY mount:
>
> * Don't write out unmount record on read-only mounts.
>
> Because of this, sequential ro mounts of a filesystem with
> a dirty log will replay the log each time, which seems odd.
>
> Fix this by writing an unmount record even for RO mounts, as long
> as norecovery wasn't specified (don't write a clean log record
> if a dirty log may still be there!) and the log device is
> writable.
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index b1469f0..62176b8 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -801,11 +801,14 @@
> int error;
>
> /*
> - * Don't write out unmount record on read-only mounts.
> + * Don't write out unmount record on norecovery mounts or ro devices.
> * Or, if we are doing a forced umount (typically because of IO errors).
> */
> - if (mp->m_flags & XFS_MOUNT_RDONLY)
> + if (mp->m_flags & XFS_MOUNT_NORECOVERY ||
> + xfs_readonly_buftarg(log->l_mp->m_logdev_targp)) {
> + ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
> return 0;
> + }
>
> error = _xfs_log_force(mp, XFS_LOG_SYNC, NULL);
> ASSERT(error || !(XLOG_FORCED_SHUTDOWN(log)));
>
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