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    Subject[PATCH 02/20] kernel: add bl_list
    Date
    From: Nick Piggin <npiggin@suse.de>

    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 hashes.

    Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Reviewed-by: Andi Kleen <ak@linux.intel.com>
    Signed-off-by: Nick Piggin <npiggin@suse.de>
    Signed-off-by: Dave Chinner <dchinner@redhat.com>
    ---
    include/linux/list_bl.h | 145 +++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/poison.h | 2 +
    2 files changed, 147 insertions(+), 0 deletions(-)
    create mode 100644 include/linux/list_bl.h

    diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
    new file mode 100644
    index 0000000..0d791ff
    --- /dev/null
    +++ b/include/linux/list_bl.h
    @@ -0,0 +1,145 @@
    +#ifndef _LINUX_LIST_BL_H
    +#define _LINUX_LIST_BL_H
    +
    +#include <linux/list.h>
    +#include <linux/bit_spinlock.h>
    +
    +/*
    + * Special version of lists, where head of the list has a bit spinlock
    + * 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.
    + */
    +
    +#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(!bit_spin_is_locked(0, (unsigned long *)&h->first));
    + 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 = BL_LIST_POISON1;
    + n->pprev = BL_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)
    +
    +#endif
    +
    +/**
    + * hlist_bl_lock - lock a hash list
    + * @h: hash list head to lock
    + */
    +static inline void hlist_bl_lock(struct hlist_bl_head *h)
    +{
    + bit_spin_lock(0, (unsigned long *)h);
    +}
    +
    +/**
    + * hlist_bl_unlock - unlock a hash list
    + * @h: hash list head to unlock
    + */
    +static inline void hlist_bl_unlock(struct hlist_bl_head *h)
    +{
    + __bit_spin_unlock(0, (unsigned long *)h);
    +}
    diff --git a/include/linux/poison.h b/include/linux/poison.h
    index 2110a81..d367d39 100644
    --- a/include/linux/poison.h
    +++ b/include/linux/poison.h
    @@ -22,6 +22,8 @@
    #define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
    #define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)

    +#define BL_LIST_POISON1 ((void *) 0x00300300 + POISON_POINTER_DELTA)
    +#define BL_LIST_POISON2 ((void *) 0x00400400 + POISON_POINTER_DELTA)
    /********** include/linux/timer.h **********/
    /*
    * Magic number "tsta" to indicate a static timer initializer
    --
    1.7.1


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