[dm-devel] [PATCH 0/3] poll()able DM events

[Mike Snitzer]

On Tue, May 09 2017 at  3:10pm -0400,
Andy Grover <agrover at redhat.com> wrote:

> Hi Mike,
> 
> We've been working off-list to develop a method of getting DM events
> that is reliable, and also can monitor events from multiple DM devices
> from a single thread.
> 
> In short, these enable an open file descriptor to /dev/mapper/control
> to be polled. If the fd indicates POLLIN, some DM device has
> experienced an event. Figuring out which is made easier by adding
> event_nr in a backwards-compatible way to DM_LIST_DEVICES, so
> userspace can compare against previously seen per-device
> event_nrs. A new ioctl is also added, to rearm the fd so it may be
> re-poll()ed. See individual patch commitlogs for more details.
> 
> Thanks to Mikulas for redeveloping earlier versions into this patchset,
> as well as the other RH LVM devs who provided early internal feedback!

I've picked this patchset up for 4.13 but this branch will likely see
quite a few more rebases until 4.12-rcX stabilizes:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=for-4.13/dm

I tweaked headers slightly and move the declaration of the variable used
in the last commit to be outside the loop.

Thought about splitting the additional 'struct file *filp' arg being
sprinkled all over in the 2nd commit, into a separate earlier commit,
but just left it as is in the end.

Mike