On 1/27/20 3:18 AM, sjpark@amazon.com wrote:

From: SeongJae Park <redacted>

Granting pages consumes backend system memory.  In systems configured
with insufficient spare memory for those pages, it can cause a memory
pressure situation.  However, finding the optimal amount of the spare
memory is challenging for large systems having dynamic resource
utilization patterns.  Also, such a static configuration might lack
flexibility.

To mitigate such problems, this patchset adds a memory reclaim callback
to 'xenbus_driver' (patch 1) and then introduce a lock for race
condition avoidance (patch 2).  After that, patch 3 applies the callback
mechanism to mitigate the problem in 'xen-blkback'.  The fourth and
fifth patches are trivial cleanups; those fix nits we found during the
development of this patchset.

Note that this patch has only trivial changes from v13.  Please refer to
below patch history for the changes.

Applied to for-linus-5.6.

-boris