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Petersen" Cc: Mike Christie , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Qiliang Yuan X-Mailer: b4 0.13.0 core_alua_free_tg_pt_gp() frees a target port group when its configfs group goes away, including the default group of every device when its backstore is deleted. Readers of lun->lun_tg_pt_gp may still hold the group, so it waits for an RCU grace period before freeing it. The wait is synchronous, so deleting a backstore spends most of its time in synchronize_rcu(), which adds up when tearing down many of them. Free the group with kfree_rcu() instead. Nothing else in the function needs the grace period to have elapsed, and kmem_cache_destroy() waits for pending kfree_rcu() calls on module unload. Deleting 256 rd_mcp backstores through configfs, five rounds alternating with and without this patch, takes (median, min-max in parentheses): backstores before (ms) after (ms) change 256 2108 (2105-2127) 692 (675-700) -67% Signed-off-by: Qiliang Yuan --- drivers/target/target_core_alua.c | 3 +-- include/target/target_core_base.h | 1 + 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c index 140154d93c430..4ef243ae843bb 100644 --- a/drivers/target/target_core_alua.c +++ b/drivers/target/target_core_alua.c @@ -1771,8 +1771,7 @@ void core_alua_free_tg_pt_gp( } spin_unlock(&tg_pt_gp->tg_pt_gp_lock); - synchronize_rcu(); - kmem_cache_free(t10_alua_tg_pt_gp_cache, tg_pt_gp); + kfree_rcu(tg_pt_gp, rcu_head); } static struct t10_alua_tg_pt_gp *core_alua_get_tg_pt_gp_by_name( diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 002b0fc575876..cec29cbec1643 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -331,6 +331,7 @@ struct t10_alua_tg_pt_gp { struct list_head tg_pt_gp_lun_list; struct se_lun *tg_pt_gp_alua_lun; struct se_node_acl *tg_pt_gp_alua_nacl; + struct rcu_head rcu_head; }; struct t10_vpd { --- base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9 change-id: 20261110-bug-target-alua-free-gp-1465539a269a Best regards, -- Qiliang Yuan