Linux Kernel  3.7.1
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blockgroup_lock.h
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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 {
39 
42 };
43 
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 *
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