include/linux/blockgroup_lock.h

   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
  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