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  1. 12 May, 2010 3 commits
    • Or Gerlitz's avatar
      IB/iser: Enhance disconnection logic for multi-pathing · 39ff05db
      Or Gerlitz authored 
      The iser connection teardown flow isn't over until the underlying
Connection Manager (e.g the IB CM) delivers a disconnected or timeout
event through the RDMA-CM.  When the remote (target) side isn't
reachable, e.g when some HW e.g port/hca/switch isn't functioning or
taken down administratively, the CM timeout flow is used and the event
may be generated only after relatively long time -- on the order of
tens of seconds.

The current iser code exposes this possibly long delay to higher
layers, specifically to the iscsid daemon and iscsi kernel stack. As a
result, the iscsi stack doesn't respond well: this low-level CM delay
is added to the fail-over time under HA schemes such as the one
provided by DM multipath through the multipathd(8) service.

This patch enhances the reference counting scheme on iser's IB
connections so that the disconnect flow initiated by iscsid from user
space (ep_disconnect) doesn't wait for the CM to deliver the
disconnect/timeout event.  (The connection teardown isn't done from
iser's view point until the event is delivered)

The iser ib (rdma) connection object is destroyed when its reference
count reaches zero.  When this happens on the RDMA-CM callback
context, extra care is taken so that the RDMA-CM does the actual
destroying of the associated ID, since doing it in the callback is
prohibited.

The reference count of iser ib connection normally reaches three,
where the <ref, deref> relations are

 1. conn <init, terminate>
 2. conn <bind, stop/destroy>
 3. cma id <create, disconnect/error/timeout callbacks>

With this patch, multipath fail-over time is about 30 seconds, while
without this patch, multipath fail-over time is about 130 seconds.
Signed-off-by: default avatarOr Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      39ff05db
    • Or Gerlitz's avatar
      IB/iser: Remove buggy back-pointer setting · d265b980
      Or Gerlitz authored 
      The iscsi connection object life cycle includes binding and unbinding
(conn_stop) to/from the iscsi transport connection object.  Since
iscsi connection objects are recycled, at the time the transport
connection (e.g iser's IB connection) is released, it is not valid to
touch the iscsi connection tied to the transport back-pointer since it
may already point to a different transport connection.
Signed-off-by: default avatarOr Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      d265b980
    • Or Gerlitz's avatar
      IB/iser: Add asynchronous event handler · 2110f9bf
      Or Gerlitz authored 
      Add handler to handle events such as port up and down.  This is useful
when testing high-availability schemes such as multi-pathing.
Signed-off-by: default avatarOr Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
      2110f9bf
  3. 09 Apr, 2010 37 commits
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