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 
36 struct bgl_lock {
37 	spinlock_t lock;
38 } ____cacheline_aligned_in_smp;
39 
40 struct blockgroup_lock {
41 	struct bgl_lock locks[NR_BG_LOCKS];
42 };
43 
bgl_lock_init(struct blockgroup_lock * bgl)44 static 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  */
56 static inline spinlock_t *
bgl_lock_ptr(struct blockgroup_lock * bgl,unsigned int block_group)57 bgl_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