From: Andy Shevchenko andriy.shevchenko@linux.intel.com
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 --- include/linux/list.h | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)
--- a/include/linux/list.h +++ b/include/linux/list.h @@ -568,6 +568,15 @@ static inline void list_splice_tail_init 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. * @head: the head for your list. @@ -575,7 +584,7 @@ static inline void list_splice_tail_init */ #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))
/** @@ -586,7 +595,7 @@ static inline void list_splice_tail_init */ #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))
/** @@ -611,7 +620,7 @@ static inline void list_splice_tail_init */ #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))
/** @@ -625,7 +634,7 @@ static inline void list_splice_tail_init */ #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))
/** @@ -637,7 +646,7 @@ static inline void list_splice_tail_init * 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))
/** @@ -650,7 +659,7 @@ static inline void list_splice_tail_init * 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))
/** @@ -663,7 +672,7 @@ static inline void list_splice_tail_init #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))
/** @@ -679,7 +688,7 @@ static inline void list_splice_tail_init #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))
/** @@ -694,7 +703,7 @@ static inline void list_splice_tail_init */ #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))
/** @@ -710,7 +719,7 @@ static inline void list_splice_tail_init #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))
/**