[dm-devel] [PATCH v2 01/17] multipathd: warn when configuration has been changed.

[Martin Wilck]

On Wed, 2020-02-05 at 12:58 -0600, Benjamin Marzinski wrote:
> It would be helpful if multipathd could log a message when
> multipath.conf or files in the config_dir have been written to, both
> so
> that it can be used to send a notification to users, and to help with
> determining after the fact if multipathd was running with an older
> config, when the logs of multipathd's behaviour don't match with the
> current multipath.conf.
> 
> To do this, the multipathd uxlsnr thread now sets up inotify watches
> on
> both /etc/multipath.conf and the config_dir to watch if the files are
> deleted or closed after being opened for writing.  In order to keep
> uxlsnr from polling repeatedly if the multipath.conf or the
> config_dir
> aren't present, it will only set up the watches once per reconfigure.
> However, since multipath.conf is far more likely to be replaced by a
> text editor than modified in place, if it gets removed, multipathd
> will
> immediately try to restart the watch on it (which will succeed if the
> file was simply replaced by a new copy).  This does mean that if
> multipath.conf or the config_dir are actually removed and then later
> re-added, multipathd won't log any more messages for changes until
> the
> next reconfigure. But that seems like a fair trade-off to avoid
> repeatedly polling for files that aren't likely to appear.
> 
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  libmultipath/config.h |   1 +
>  multipathd/main.c     |   1 +
>  multipathd/uxlsnr.c   | 138
> ++++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 134 insertions(+), 6 deletions(-)

Reviewed-by: Martin Wilck <mwilck at suse.com>