Share size limited by share type

Add support for limit the size of share through the share type, the
share created by the user shall not be greater than the maximum value
set in the share type and shall not be less than the minimum value set.
Of course, depending on the usage scenario, only a maximum or a minimum
can be set.

Partially-Implements: blueprint share-size-limited-by-share-type
Change-Id: Ie03a4564ddcacd9b084db09b76be55d15080133f

specs/wallaby/share-size-limited-by-share-type.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+===========================================
+The share size can be limited by share type
+===========================================
+
+https://blueprints.launchpad.net/manila/+spec/share-size-limited-by-share-type
+
+Add support for limit the size of share through the share type, the share
+created by the user shall not be greater than the maximum value set in the
+share type and shall not be less than the minimum value set. Of course,
+depending on the usage scenario, only a maximum or a minimum can be set.
+
+Problem description
+===================
+
+In some usage scenarios, we do not want users to create too large share size,
+then affect the number of shares that can be created, maybe limited by project
+quota or backend storage, or in some usage scenarios, creating a share that
+is too small makes no sense. So administrators desperately need a way to limit
+the size of share created by users.
+
+Use Cases
+=========
+
+In scenarios where storage backend capacity is small, or project quota is
+limited and the number of users is high, In order to enable more users to
+create their own share, Administrators need to limit the maximum size of each
+share. In other scenarios, if the share is too small to ensure the normal
+operation of the business, the administrator needs to set the minimum value
+of each share. Administrator can also set the maximum and minimum values of
+share according to actual needs.
+
+Proposed change
+===============
+
+The following changes are proposed:
+
+* Two new extra_specs keys of share type are added for support set the minimum
+  share size and maximum share size.
+
+  * **provisioning:min_share_size** Set the minimum size of share by the
+    share type.
+  * **provisioning:max_share_size** Set the maximum size of share by the
+    share type.
+
+* The value of these keys is a positive integer, the unit defaults to GB.
+* These two extra specifications will be visible to end users. If they're not
+  set, it is assumed that there are no share size limits enforced by the share
+  type, but limits may be enforced by the service and the user's quotas.
+
+Alternatives
+------------
+
+None
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+The size restrictions will be checked at the API level as part of share
+creation, extend, shrink or migration.
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None.
+
+Other end user impact
+---------------------
+
+The size of the share created by the end user will be limited by the share
+type if set specified keys in extra_specs in share type. Operations including
+extend, shrink, and migration operations are also subject to this restriction.
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  haixin<haixin@inspur.com>
+
+
+Work Items
+----------
+
+* Add size check in API level
+* Add related unit and functional tests
+* Add docs update
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+1. Unit test to test whether these keys restrictions are in effect.
+2. Tempest test whether set keys work correctly from API perspective.
+
+Documentation Impact
+====================
+
+1. The manila API documentation will need to be updated to reflect extra_specs
+   of share type support two more keys.
+
+References
+==========
+
+None