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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: Or Gerlitz <ogerlitz@voltaire.com> Signed-off-by: Roland Dreier <rolandd@cisco.com> |
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| .. | ||
| iscsi_iser.c | ||
| iscsi_iser.h | ||
| iser_initiator.c | ||
| iser_memory.c | ||
| iser_verbs.c | ||
| Kconfig | ||
| Makefile | ||