Commit e1308161 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Linus Torvalds
Browse files

include/linux/list.h: add a macro to test if entry is pointing to the head 



Add a macro to test if entry is pointing to the head of the list which is
useful in cases like:

  list_for_each_entry(pos, &head, member) {
    if (cond)
      break;
  }
  if (list_entry_is_head(pos, &head, member))
    return -ERRNO;

that allows to avoid additional variable to be added to track if loop has
not been stopped in the middle.

While here, convert list_for_each_entry*() family of macros to use a new one.

Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarCezary Rojewski <cezary.rojewski@intel.com>
Link: https://lkml.kernel.org/r/20200929134342.51489-1-andriy.shevchenko@linux.intel.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1d339638

include/linux/list.h

+19 −10
Original line number Diff line number Diff line
@@ -609,6 +609,15 @@ static inline void list_splice_tail_init(struct list_head *list, 
	     pos != (head); \

	     pos = n, n = pos->prev)



/**

 * list_entry_is_head - test if the entry points to the head of the list

 * @pos:	the type * to cursor

 * @head:	the head for your list.

 * @member:	the name of the list_head within the struct.

 */

#define list_entry_is_head(pos, head, member)				\

	(&pos->member == (head))



/**

 * list_for_each_entry	-	iterate over list of given type

 * @pos:	the type * to use as a loop cursor.
@@ -617,7 +626,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 */

#define list_for_each_entry(pos, head, member)				\

	for (pos = list_first_entry(head, typeof(*pos), member);	\

	     &pos->member != (head);					\

	     !list_entry_is_head(pos, head, member);			\

	     pos = list_next_entry(pos, member))



/**
@@ -628,7 +637,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 */

#define list_for_each_entry_reverse(pos, head, member)			\

	for (pos = list_last_entry(head, typeof(*pos), member);		\

	     &pos->member != (head); 					\

	     !list_entry_is_head(pos, head, member); 			\

	     pos = list_prev_entry(pos, member))



/**
@@ -653,7 +662,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 */

#define list_for_each_entry_continue(pos, head, member) 		\

	for (pos = list_next_entry(pos, member);			\

	     &pos->member != (head);					\

	     !list_entry_is_head(pos, head, member);			\

	     pos = list_next_entry(pos, member))



/**
@@ -667,7 +676,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 */

#define list_for_each_entry_continue_reverse(pos, head, member)		\

	for (pos = list_prev_entry(pos, member);			\

	     &pos->member != (head);					\

	     !list_entry_is_head(pos, head, member);			\

	     pos = list_prev_entry(pos, member))



/**
@@ -679,7 +688,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 * Iterate over list of given type, continuing from current position.

 */

#define list_for_each_entry_from(pos, head, member) 			\

	for (; &pos->member != (head);					\

	for (; !list_entry_is_head(pos, head, member);			\

	     pos = list_next_entry(pos, member))



/**
@@ -692,7 +701,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 * Iterate backwards over list of given type, continuing from current position.

 */

#define list_for_each_entry_from_reverse(pos, head, member)		\

	for (; &pos->member != (head);					\

	for (; !list_entry_is_head(pos, head, member);			\

	     pos = list_prev_entry(pos, member))



/**
@@ -705,7 +714,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
#define list_for_each_entry_safe(pos, n, head, member)			\

	for (pos = list_first_entry(head, typeof(*pos), member),	\

		n = list_next_entry(pos, member);			\

	     &pos->member != (head); 					\

	     !list_entry_is_head(pos, head, member); 			\

	     pos = n, n = list_next_entry(n, member))



/**
@@ -721,7 +730,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
#define list_for_each_entry_safe_continue(pos, n, head, member) 		\

	for (pos = list_next_entry(pos, member), 				\

		n = list_next_entry(pos, member);				\

	     &pos->member != (head);						\

	     !list_entry_is_head(pos, head, member);				\

	     pos = n, n = list_next_entry(n, member))



/**
@@ -736,7 +745,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
 */

#define list_for_each_entry_safe_from(pos, n, head, member) 			\

	for (n = list_next_entry(pos, member);					\

	     &pos->member != (head);						\

	     !list_entry_is_head(pos, head, member);				\

	     pos = n, n = list_next_entry(n, member))



/**
@@ -752,7 +761,7 @@ static inline void list_splice_tail_init(struct list_head *list, 
#define list_for_each_entry_safe_reverse(pos, n, head, member)		\

	for (pos = list_last_entry(head, typeof(*pos), member),		\

		n = list_prev_entry(pos, member);			\

	     &pos->member != (head); 					\

	     !list_entry_is_head(pos, head, member); 			\

	     pos = n, n = list_prev_entry(n, member))



/**

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