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