From: Andy Shevchenko <andriy.shevchenko@linux.intel.com> stable inclusion from linux-4.19.207 commit 386a913d4960a83cc4657ebe0c9bc462d8f5e2a1 -------------------------------- commit e130816164e244b692921de49771eeb28205152d upstream. 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: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com> Link: https://lkml.kernel.org/r/20200929134342.51489-1-andriy.shevchenko@linux.int... Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- include/linux/list.h | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index fc0e87f94d286..6b7f633122dd6 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -494,6 +494,15 @@ 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. @@ -502,7 +511,7 @@ 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)) /** @@ -513,7 +522,7 @@ 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)) /** @@ -538,7 +547,7 @@ 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)) /** @@ -552,7 +561,7 @@ 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)) /** @@ -564,7 +573,7 @@ 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)) /** @@ -577,7 +586,7 @@ 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)) /** @@ -590,7 +599,7 @@ 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)) /** @@ -606,7 +615,7 @@ 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)) /** @@ -621,7 +630,7 @@ 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)) /** @@ -637,7 +646,7 @@ 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)) /** -- 2.25.1