fs/reiserfs/lock.c

   1 #include "reiserfs.h"
   2 #include <linux/mutex.h>
   3
   4 /*
   5  * The previous reiserfs locking scheme was heavily based on
   6  * the tricky properties of the Bkl:
   7  *
   8  * - it was acquired recursively by a same task
   9  * - the performances relied on the release-while-schedule() property
  10  *
  11  * Now that we replace it by a mutex, we still want to keep the same
  12  * recursive property to avoid big changes in the code structure.
  13  * We use our own lock_owner here because the owner field on a mutex
  14  * is only available in SMP or mutex debugging, also we only need this field
  15  * for this mutex, no need for a system wide mutex facility.
  16  *
  17  * Also this lock is often released before a call that could block because
  18  * reiserfs performances were partially based on the release while schedule()
  19  * property of the Bkl.
  20  */
  21 void reiserfs_write_lock(struct super_block *s)
  22 {
  23         struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
  24
  25         if (sb_i->lock_owner != current) {
  26                 mutex_lock(&sb_i->lock);
  27                 sb_i->lock_owner = current;
  28         }
  29
  30         /* No need to protect it, only the current task touches it */
  31         sb_i->lock_depth++;
  32 }
  33
  34 void reiserfs_write_unlock(struct super_block *s)
  35 {
  36         struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
  37
  38         /*
  39          * Are we unlocking without even holding the lock?
  40          * Such a situation must raise a BUG() if we don't want
  41          * to corrupt the data.
  42          */
  43         BUG_ON(sb_i->lock_owner != current);
  44
  45         if (--sb_i->lock_depth == -1) {
  46                 sb_i->lock_owner = NULL;
  47                 mutex_unlock(&sb_i->lock);
  48         }
  49 }
  50
  51 int __must_check reiserfs_write_unlock_nested(struct super_block *s)
  52 {
  53         struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
  54         int depth;
  55
  56         /* this can happen when the lock isn't always held */
  57         if (sb_i->lock_owner != current)
  58                 return -1;
  59
  60         depth = sb_i->lock_depth;
  61
  62         sb_i->lock_depth = -1;
  63         sb_i->lock_owner = NULL;
  64         mutex_unlock(&sb_i->lock);
  65
  66         return depth;
  67 }
  68
  69 void reiserfs_write_lock_nested(struct super_block *s, int depth)
  70 {
  71         struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
  72
  73         /* this can happen when the lock isn't always held */
  74         if (depth == -1)
  75                 return;
  76
  77         mutex_lock(&sb_i->lock);
  78         sb_i->lock_owner = current;
  79         sb_i->lock_depth = depth;
  80 }
  81
  82 /*
  83  * Utility function to force a BUG if it is called without the superblock
  84  * write lock held.  caller is the string printed just before calling BUG()
  85  */
  86 void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
  87 {
  88         struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
  89
  90         WARN_ON(sb_i->lock_depth < 0);
  91 }
  92
  93 #ifdef CONFIG_REISERFS_CHECK
  94 void reiserfs_lock_check_recursive(struct super_block *sb)
  95 {
  96         struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
  97
  98         WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
  99 }
 100 #endif