staging: lustre: add container_of_safe()

Luster has a container_of0() function which is similar to
container_of() but passes an IS_ERR_OR_NULL() pointer through
unchanged.
This could be generally useful: bcache at last has a similar function.

Naming is hard, but the precedent set by hlist_entry_safe() suggests
a _safe suffix might be most consistent.

So add container_of_safe() to kernel.h, and replace all occurrences of
container_of0() with one of
  - list_first_entry, list_next_entry, when that is a better fit,
  - container_of(), when the pointer is used as a validpointer in
    surrounding code,
  - container_of_safe() when there is no obviously better alternative.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/staging/lustre/lustre/llite/vvp_internal.h b/drivers/staging/lustre/lustre/llite/vvp_internal.h
index 02ea5161d635..7d3abb43584a 100644
--- a/drivers/staging/lustre/lustre/llite/vvp_internal.h
+++ b/drivers/staging/lustre/lustre/llite/vvp_internal.h
@@ -263,22 +263,22 @@ static inline struct lu_device *vvp2lu_dev(struct vvp_device *vdv)
 
 static inline struct vvp_device *lu2vvp_dev(const struct lu_device *d)
 {
-	return container_of0(d, struct vvp_device, vdv_cl.cd_lu_dev);
+	return container_of_safe(d, struct vvp_device, vdv_cl.cd_lu_dev);
 }
 
 static inline struct vvp_device *cl2vvp_dev(const struct cl_device *d)
 {
-	return container_of0(d, struct vvp_device, vdv_cl);
+	return container_of_safe(d, struct vvp_device, vdv_cl);
 }
 
 static inline struct vvp_object *cl2vvp(const struct cl_object *obj)
 {
-	return container_of0(obj, struct vvp_object, vob_cl);
+	return container_of_safe(obj, struct vvp_object, vob_cl);
 }
 
 static inline struct vvp_object *lu2vvp(const struct lu_object *obj)
 {
-	return container_of0(obj, struct vvp_object, vob_cl.co_lu);
+	return container_of_safe(obj, struct vvp_object, vob_cl.co_lu);
 }
 
 static inline struct inode *vvp_object_inode(const struct cl_object *obj)