From 4e35e6070b1ceed89c3bba2af4216c286fb1dafd Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:50:03 +1100 Subject: kernel: add bl_list Introduce a type of hlist that can support the use of the lowest bit in the hlist_head. This will be subsequently used to implement per-bucket bit spinlock for inode and dentry hashes, and may be useful in other cases such as network hashes. Reviewed-by: Paul E. McKenney Signed-off-by: Nick Piggin --- include/linux/list_bl.h | 144 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 include/linux/list_bl.h (limited to 'include/linux/list_bl.h') diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h new file mode 100644 index 000000000000..9ee97e7f2be4 --- /dev/null +++ b/include/linux/list_bl.h @@ -0,0 +1,144 @@ +#ifndef _LINUX_LIST_BL_H +#define _LINUX_LIST_BL_H + +#include + +/* + * Special version of lists, where head of the list has a lock in the lowest + * bit. This is useful for scalable hash tables without increasing memory + * footprint overhead. + * + * For modification operations, the 0 bit of hlist_bl_head->first + * pointer must be set. + * + * With some small modifications, this can easily be adapted to store several + * arbitrary bits (not just a single lock bit), if the need arises to store + * some fast and compact auxiliary data. + */ + +#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) +#define LIST_BL_LOCKMASK 1UL +#else +#define LIST_BL_LOCKMASK 0UL +#endif + +#ifdef CONFIG_DEBUG_LIST +#define LIST_BL_BUG_ON(x) BUG_ON(x) +#else +#define LIST_BL_BUG_ON(x) +#endif + + +struct hlist_bl_head { + struct hlist_bl_node *first; +}; + +struct hlist_bl_node { + struct hlist_bl_node *next, **pprev; +}; +#define INIT_HLIST_BL_HEAD(ptr) \ + ((ptr)->first = NULL) + +static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h) +{ + h->next = NULL; + h->pprev = NULL; +} + +#define hlist_bl_entry(ptr, type, member) container_of(ptr,type,member) + +static inline int hlist_bl_unhashed(const struct hlist_bl_node *h) +{ + return !h->pprev; +} + +static inline struct hlist_bl_node *hlist_bl_first(struct hlist_bl_head *h) +{ + return (struct hlist_bl_node *) + ((unsigned long)h->first & ~LIST_BL_LOCKMASK); +} + +static inline void hlist_bl_set_first(struct hlist_bl_head *h, + struct hlist_bl_node *n) +{ + LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); + LIST_BL_BUG_ON(!((unsigned long)h->first & LIST_BL_LOCKMASK)); + h->first = (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK); +} + +static inline int hlist_bl_empty(const struct hlist_bl_head *h) +{ + return !((unsigned long)h->first & ~LIST_BL_LOCKMASK); +} + +static inline void hlist_bl_add_head(struct hlist_bl_node *n, + struct hlist_bl_head *h) +{ + struct hlist_bl_node *first = hlist_bl_first(h); + + n->next = first; + if (first) + first->pprev = &n->next; + n->pprev = &h->first; + hlist_bl_set_first(h, n); +} + +static inline void __hlist_bl_del(struct hlist_bl_node *n) +{ + struct hlist_bl_node *next = n->next; + struct hlist_bl_node **pprev = n->pprev; + + LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK); + + /* pprev may be `first`, so be careful not to lose the lock bit */ + *pprev = (struct hlist_bl_node *) + ((unsigned long)next | + ((unsigned long)*pprev & LIST_BL_LOCKMASK)); + if (next) + next->pprev = pprev; +} + +static inline void hlist_bl_del(struct hlist_bl_node *n) +{ + __hlist_bl_del(n); + n->next = LIST_POISON1; + n->pprev = LIST_POISON2; +} + +static inline void hlist_bl_del_init(struct hlist_bl_node *n) +{ + if (!hlist_bl_unhashed(n)) { + __hlist_bl_del(n); + INIT_HLIST_BL_NODE(n); + } +} + +/** + * hlist_bl_for_each_entry - iterate over list of given type + * @tpos: the type * to use as a loop cursor. + * @pos: the &struct hlist_node to use as a loop cursor. + * @head: the head for your list. + * @member: the name of the hlist_node within the struct. + * + */ +#define hlist_bl_for_each_entry(tpos, pos, head, member) \ + for (pos = hlist_bl_first(head); \ + pos && \ + ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ + pos = pos->next) + +/** + * hlist_bl_for_each_entry_safe - iterate over list of given type safe against removal of list entry + * @tpos: the type * to use as a loop cursor. + * @pos: the &struct hlist_node to use as a loop cursor. + * @n: another &struct hlist_node to use as temporary storage + * @head: the head for your list. + * @member: the name of the hlist_node within the struct. + */ +#define hlist_bl_for_each_entry_safe(tpos, pos, n, head, member) \ + for (pos = hlist_bl_first(head); \ + pos && ({ n = pos->next; 1; }) && \ + ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1;}); \ + pos = n) + +#endif -- cgit v1.2.3-59-g8ed1b