[PATCH 09/33] configfs: Introduce config_item_get_unless_zero()

[Bart Van Assche <bart.vanassche@sandisk.com>]

This new function is needed to fix a deadlock in the SCSI target
XCOPY implementation.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: linux-fsdevel@vger.kernel.org
---
 fs/configfs/item.c       | 6 ++++++
 include/linux/configfs.h | 1 +
 2 files changed, 7 insertions(+)

diff --git a/fs/configfs/item.c b/fs/configfs/item.c
index 8b2a994042dd..e3501b9bbb60 100644
--- a/fs/configfs/item.c
+++ b/fs/configfs/item.c
@@ -138,6 +138,12 @@ struct config_item *config_item_get(struct config_item *item)
 }
 EXPORT_SYMBOL(config_item_get);
 
+struct config_item *config_item_get_unless_zero(struct config_item *item)
+{
+	return item && kref_get_unless_zero(&item->ci_kref) ? item : NULL;
+}
+EXPORT_SYMBOL(config_item_get_unless_zero);
+
 static void config_item_cleanup(struct config_item *item)
 {
 	struct config_item_type *t = item->ci_type;
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 2319b8c108e8..406e16dabc28 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -75,6 +75,7 @@ extern void config_item_init_type_name(struct config_item *item,
 				       struct config_item_type *type);
 
 extern struct config_item * config_item_get(struct config_item *);
+extern struct config_item * config_item_get_unless_zero(struct config_item *);
 extern void config_item_put(struct config_item *);
 
 struct config_item_type {
-- 
2.12.2