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  1. 27 Feb, 2017 3 commits
    • Nicholas Bellinger's avatar
      target: Add counters for ABORT_TASK success + failure · c87ba9c4
      Nicholas Bellinger authored 
      This patch introduces two counters for ABORT_TASK success +
failure under:

   /sys/kernel/config/target/core/$HBA/$DEV/statistics/scsi_tgt_dev/

that are useful for diagnosing various backend device latency
and front fabric issues.

Normally when folks see alot of aborts_complete happening,
it means the backend device I/O completion latency is high,
and not returning completions fast enough before host side
timeouts trigger.

And normally when folks see alot of aborts_no_task, it means
completions are being posted by target-core into fabric driver
code, but the responses aren't making it back to the host.
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
      c87ba9c4
    • Nicholas Bellinger's avatar
      iscsi-target: Fix early login failure statistics misses · 17c61ad6
      Nicholas Bellinger authored 
      Due to the long standing checks in iscsit_snmp_get_tiqn()
that assume conn->sess->tpg dereference of tpg->tpg_tiqn
for iscsit_collect_login_stats() usage, some of the early
login failure cases like ISCSI_LOGIN_STATUS_TGT_FORBIDDEN
where not getting incremented, due to sess->tpg assignment
happening later in iscsi_login_zero_tsih_s2().

Instead, use the earlier conn->tpg assignment done by
iscsi_target_locate_portal() -> iscsit_get_tpg_from_np()
so the existing counters are incremented correctly for
the various early login failure cases.

Also, go ahead and drop the old rate limiting check in
iscsit_collect_login_stats(), so we get the true number
of failed login attempts in the existing statistics.
Reported-by: default avatarRyan Stiles <ras@datera.io>
Cc: Ryan Stiles <ras@datera.io>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
      17c61ad6
    • Nicholas Bellinger's avatar
      target: Fix NULL dereference during LUN lookup + active I/O shutdown · bd4e2d29
      Nicholas Bellinger authored 
      When transport_clear_lun_ref() is shutting down a se_lun via
configfs with new I/O in-flight, it's possible to trigger a
NULL pointer dereference in transport_lookup_cmd_lun() due
to the fact percpu_ref_get() doesn't do any __PERCPU_REF_DEAD
checking before incrementing lun->lun_ref.count after
lun->lun_ref has switched to atomic_t mode.

This results in a NULL pointer dereference as LUN shutdown
code in core_tpg_remove_lun() continues running after the
existing ->release() -> core_tpg_lun_ref_release() callback
completes, and clears the RCU protected se_lun->lun_se_dev
pointer.

During the OOPs, the state of lun->lun_ref in the process
which triggered the NULL pointer dereference looks like
the following on v4.1.y stable code:

struct se_lun {
  lun_link_magic = 4294932337,
  lun_status = TRANSPORT_LUN_STATUS_FREE,

  .....

  lun_se_dev = 0x0,
  lun_sep = 0x0,

  .....

  lun_ref = {
    count = {
      counter = 1
    },
    percpu_count_ptr = 3,
    release = 0xffffffffa02fa1e0 <core_tpg_lun_ref_release>,
    confirm_switch = 0x0,
    force_atomic = false,
    rcu = {
      next = 0xffff88154fa1a5d0,
      func = 0xffffffff8137c4c0 <percpu_ref_switch_to_atomic_rcu>
    }
  }
}

To address this bug, use percpu_ref_tryget_live() to ensure
once __PERCPU_REF_DEAD is visable on all CPUs and ->lun_ref
has switched to atomic_t, all new I/Os will fail to obtain
a new lun->lun_ref reference.

Also use an explicit percpu_ref_kill_and_confirm() callback
to block on ->lun_ref_comp to allow the first stage and
associated RCU grace period to complete, and then block on
->lun_ref_shutdown waiting for the final percpu_ref_put()
to drop the last reference via transport_lun_remove_cmd()
before continuing with core_tpg_remove_lun() shutdown.
Reported-by: default avatarRob Millner <rlm@daterainc.com>
Tested-by: default avatarRob Millner <rlm@daterainc.com>
Cc: Rob Millner <rlm@daterainc.com>
Tested-by: default avatarVaibhav Tandon <vst@datera.io>
Cc: Vaibhav Tandon <vst@datera.io>
Tested-by: default avatarBryant G. Ly <bryantly@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # v3.14+
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
      bd4e2d29
  3. 20 Feb, 2017 2 commits
  5. 19 Feb, 2017 9 commits
  7. 09 Feb, 2017 26 commits
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