include/linux/blockgroup_lock.h

#ifndef _LINUX_BLOCKGROUP_LOCK_H
#define _LINUX_BLOCKGROUP_LOCK_H
/*
 * Per-blockgroup locking for ext2 and ext3.
 *
 * Simple hashed spinlocking.
 */

#include <linux/spinlock.h>
#include <linux/cache.h>

#ifdef CONFIG_SMP
#define NR_BG_LOCKS	(4 << ilog2(NR_CPUS < 32 ? NR_CPUS : 32))
#else
#define NR_BG_LOCKS	1
#endif

struct bgl_lock {
	spinlock_t lock;
} ____cacheline_aligned_in_smp;

struct blockgroup_lock {
	struct bgl_lock locks[NR_BG_LOCKS];
};

static inline void bgl_lock_init(struct blockgroup_lock *bgl)
{
	int i;

	for (i = 0; i < NR_BG_LOCKS; i++)
		spin_lock_init(&bgl->locks[i].lock);
}

static inline spinlock_t *
bgl_lock_ptr(struct blockgroup_lock *bgl, unsigned int block_group)
{
	return &bgl->locks[block_group & (NR_BG_LOCKS-1)].lock;
}

#endif