Re: [Scst-devel] [PATCH v3] SCST User Settable "active" Attribute

[Vladislav B. <vs...@vl...>]

Committed, thanks!

Vlad

Marc Smith wrote on 07/25/2017 08:50 AM:
> In the current implementation of SCST/trunk the recently introduced
> "active" attribute for vdisk_blockio devices is managed by an ALUA
> state change (start/finish), for specific ALUA states (eg,
> active/standby). Relying on ALUA state changes to open/close the
> back-end block device does indeed work for some SCST configurations,
> however, some users desire advanced control over this setting, and
> prefer to handle opening/closing a back-end block device from the
> cluster resource agent (RA) script. Certain ambiguous situations can
> also arise if more than one target group exists per SCST device
> group... in this case, a back-end device may flip/flop (opened/closed)
> and may end up in an inconsistent state if care is not taken in the
> implementation of the cluster RA.
> 
> The patch below makes the "active" sysfs attribute for vdisk_blockio
> readable/writable by a user, thereby giving full control over a
> device's opened/closed state. The default behavior for SCST
> vdisk_blockio devices is to allow ALUA state changes to control the
> opened/closed ("active") state of a back-end device
> (bind_alua_state=1). If the user wishes to handle setting the "active"
> attribute themselves via a script or cluster RA, they would set
> bind_alua_state=0 for the vdisk_blockio device, and the "active"
> attribute would not be modified on ALUA state changes, it is then left
> up to the user to handle this.
> 
> The patch below also fixes a bug where the attribute value is not
> changed when the appropriate ALUA state is set, unless a target
> session exists for the target group target; see here for more
> information: https://sourceforge.net/p/scst/mailman/message/35898014/
> 
> 
> Changes since v2:
> - Rebase against trunk/r7211
> - Added documentation for the active and bind_alua_state attributes in
> the "VDISK device handler" section of README and README_in-tree
> Changes since v1:
> - Added missing 'bind_alua_state' attribute to vdisk_blk_devtype
> member add_device_parameters
> - Parse the 'bind_alua_state' attribute in vdev_parse_add_dev_params()
> - And 'bind_alua_state' is needed in allowed_params[] of
> vdev_blockio_add_device()
> 
> 
> Signed-off-by: Marc A. Smith <mar...@pa...>