[PATCH 3/4] target: Move core_alua_free_lu_gp() into ->release() callback

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch moves the core_alua_free_lu_gp() and subsequent release of
struct t10_alua_lu_gp memory to inside of the configfs callback
target_core_alua_lu_gp_ops->release() called from within
fs/configfs/item.c:config_item_cleanup() context.  This patch resolves the
following SLUB 'Poison overwritten' warning when calling core_alua_free_lu_gp()
-> kfree(lu_gp) directly after config_item_put():

[  293.452366] =============================================================================
[  293.452653] BUG t10_alua_lu_gp_cache: Poison overwritten
[  293.452653] -----------------------------------------------------------------------------
[  293.452653]
[  293.452653] INFO: 0xffff88001f7c2174-0xffff88001f7c2174. First byte 0x6a instead of 0x6b
[  293.452653] INFO: Allocated in core_alua_allocate_lu_gp+0x1c/0xa0 [target_core_mod] age=1799 cpu=0 pid=5229
[  293.452653] INFO: Freed in core_alua_free_lu_gp+0x105/0x111 [target_core_mod] age=52 cpu=0 pid=5235
[  293.452653] INFO: Slab 0xffffea00006e3270 objects=25 used=0 fp=0xffff88001f7c2000 flags=0x100000000004080
[  293.452653] INFO: Object 0xffff88001f7c2140 @offset=320 fp=0xffff88001f7c2280
[  293.452653]

Cc: Joel Becker <jlbec@evilplan.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
---
 drivers/target/target_core_configfs.c |   15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 3715c91..3933409 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -2195,7 +2195,16 @@ static struct configfs_attribute *target_core_alua_lu_gp_attrs[] = {
 	NULL,
 };
 
+static void target_core_alua_lu_gp_release(struct config_item *item)
+{
+	struct t10_alua_lu_gp *lu_gp = container_of(to_config_group(item),
+			struct t10_alua_lu_gp, lu_gp_group);
+
+	core_alua_free_lu_gp(lu_gp);
+}
+
 static struct configfs_item_operations target_core_alua_lu_gp_ops = {
+	.release		= target_core_alua_lu_gp_release,
 	.show_attribute		= target_core_alua_lu_gp_attr_show,
 	.store_attribute	= target_core_alua_lu_gp_attr_store,
 };
@@ -2246,9 +2255,11 @@ static void target_core_alua_drop_lu_gp(
 	printk(KERN_INFO "Target_Core_ConfigFS: Releasing ALUA Logical Unit"
 		" Group: core/alua/lu_gps/%s, ID: %hu\n",
 		config_item_name(item), lu_gp->lu_gp_id);
-
+	/*
+	 * core_alua_free_lu_gp() is called from target_core_alua_lu_gp_ops->release()
+	 * -> target_core_alua_lu_gp_release()
+	 */
 	config_item_put(item);
-	core_alua_free_lu_gp(lu_gp);
 }
 
 static struct configfs_group_operations target_core_alua_lu_gps_group_ops = {
-- 
1.5.6.5