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>
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 6a1eb0b..58d6645 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -964,6 +964,22 @@
"pointer type mismatch in container_of()"); \
((type *)(__mptr - offsetof(type, member))); })
+/**
+ * container_of_safe - cast a member of a structure out to the containing structure
+ * @ptr: the pointer to the member.
+ * @type: the type of the container struct this is embedded in.
+ * @member: the name of the member within the struct.
+ *
+ * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
+ */
+#define container_of_safe(ptr, type, member) ({ \
+ void *__mptr = (void *)(ptr); \
+ BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
+ !__same_type(*(ptr), void), \
+ "pointer type mismatch in container_of()"); \
+ IS_ERR_OR_NULL(ptr) ? ERR_CAST(ptr) : \
+ ((type *)(__mptr - offsetof(type, member))); })
+
/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
#ifdef CONFIG_FTRACE_MCOUNT_RECORD
# define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD