LXR linux-bk/include/linux/blockgroup

   1#ifndef _LINUX_BLOCKGROUP_LOCK_H
   2#define _LINUX_BLOCKGROUP_LOCK_H
   3/*
   4 * Per-blockgroup locking for ext2 and ext3.
   5 *
   6 * Simple hashed spinlocking.
   7 */
   8
   9#include <linux/config.h>
  10#include <linux/spinlock.h>
  11#include <linux/cache.h>
  12
  13#ifdef CONFIG_SMP
  14
  15/*
  16 * We want a power-of-two.  Is there a better way than this?
  17 */
  18
  19#if NR_CPUS >= 32
  20#define NR_BG_LOCKS     128
  21#elif NR_CPUS >= 16
  22#define NR_BG_LOCKS     64
  23#elif NR_CPUS >= 8
  24#define NR_BG_LOCKS     32
  25#elif NR_CPUS >= 4
  26#define NR_BG_LOCKS     16
  27#elif NR_CPUS >= 2
  28#define NR_BG_LOCKS     8
  29#else
  30#define NR_BG_LOCKS     4
  31#endif
  32
  33#else   /* CONFIG_SMP */
  34#define NR_BG_LOCKS     1
  35#endif  /* CONFIG_SMP */
  36
  37struct bgl_lock {
  38        spinlock_t lock;
  39} ____cacheline_aligned_in_smp;
  40
  41struct blockgroup_lock {
  42        struct bgl_lock locks[NR_BG_LOCKS];
  43};
  44
  45static inline void bgl_lock_init(struct blockgroup_lock *bgl)
  46{
  47        int i;
  48
  49        for (i = 0; i < NR_BG_LOCKS; i++)
  50                spin_lock_init(&bgl->locks[i].lock);
  51}
  52
  53/*
  54 * The accessor is a macro so we can embed a blockgroup_lock into different
  55 * superblock types
  56 */
  57#define sb_bgl_lock(sb, block_group) \
  58        (&(sb)->s_blockgroup_lock.locks[(block_group) & (NR_BG_LOCKS-1)].lock)
  59
  60#endif
  61