blockgroup_lock.h
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#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
/*
* We want a power-of-two. Is there a better way than this?
*/
#if NR_CPUS >= 32
#define NR_BG_LOCKS 128
#elif NR_CPUS >= 16
#define NR_BG_LOCKS 64
#elif NR_CPUS >= 8
#define NR_BG_LOCKS 32
#elif NR_CPUS >= 4
#define NR_BG_LOCKS 16
#elif NR_CPUS >= 2
#define NR_BG_LOCKS 8
#else
#define NR_BG_LOCKS 4
#endif
#else /* CONFIG_SMP */
#define NR_BG_LOCKS 1
#endif /* CONFIG_SMP */
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);
}
/*
* The accessor is a macro so we can embed a blockgroup_lock into different
* superblock types
*/
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