[PATCH 0/2] scsi: target: alua: Skip grace periods on LUN add and remove

[Qiliang Yuan <qiliang.yuan@linux.dev>]

Creating or removing a LUN through configfs attaches it to, or detaches
it from, its ALUA target port group, and both helpers wait for an RCU
grace period afterwards.

Neither wait protects anything, yet each costs one grace period per
LUN, which adds up to seconds when exporting or tearing down many LUNs,
e.g. when targetcli restores a saved configuration.

Drop the wait on attach (patch 1) and on detach (patch 2).

Adding and removing 256 LUNs of an iSCSI TPG through configfs, five
rounds alternating with and without the series, takes (median, min-max
in parentheses):

  256 LUNs  before (ms)       after (ms)        change
  add       3144 (3104-3175)  1379 (1277-1393)    -56%
  remove    5222 (5165-5244)  3551 (3436-3810)    -32%

Signed-off-by: Qiliang Yuan <qiliang.yuan@linux.dev>
---
Qiliang Yuan (2):
      scsi: target: alua: Don't wait for a grace period when attaching a LUN
      scsi: target: alua: Drop the grace period wait from LUN detach

 drivers/target/target_core_alua.c | 2 --
 1 file changed, 2 deletions(-)
---
base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9
change-id: 20261110-bug-target-alua-lun-gp-b410ef8d1144

Best regards,
-- 
Qiliang Yuan <qiliang.yuan@linux.dev>