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/spinlock.h>
10#include <linux/cache.h>
11
12#ifdef CONFIG_SMP
13
14/*
15 * We want a power-of-two.  Is there a better way than this?
16 */
17
18#if NR_CPUS >= 32
19#define NR_BG_LOCKS	128
20#elif NR_CPUS >= 16
21#define NR_BG_LOCKS	64
22#elif NR_CPUS >= 8
23#define NR_BG_LOCKS	32
24#elif NR_CPUS >= 4
25#define NR_BG_LOCKS	16
26#elif NR_CPUS >= 2
27#define NR_BG_LOCKS	8
28#else
29#define NR_BG_LOCKS	4
30#endif
31
32#else	/* CONFIG_SMP */
33#define NR_BG_LOCKS	1
34#endif	/* CONFIG_SMP */
35
36struct bgl_lock {
37	spinlock_t lock;
38} ____cacheline_aligned_in_smp;
39
40struct blockgroup_lock {
41	struct bgl_lock locks[NR_BG_LOCKS];
42};
43
44static inline void bgl_lock_init(struct blockgroup_lock *bgl)
45{
46	int i;
47
48	for (i = 0; i < NR_BG_LOCKS; i++)
49		spin_lock_init(&bgl->locks[i].lock);
50}
51
52/*
53 * The accessor is a macro so we can embed a blockgroup_lock into different
54 * superblock types
55 */
56static inline spinlock_t *
57bgl_lock_ptr(struct blockgroup_lock *bgl, unsigned int block_group)
58{
59	return &bgl->locks[(block_group) & (NR_BG_LOCKS-1)].lock;
60}
61
62#endif
63