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 /*
  52  * If we already own the lock, just exit and don't increase the depth.
  53  * Useful when we don't want to lock more than once.
  54  *
  55  * We always return the lock_depth we had before calling
  56  * this function.
  57  */
  58 int reiserfs_write_lock_once(struct super_block *s)
  59 {
  60         struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
  61
  62         if (sb_i->lock_owner != current) {
  63                 mutex_lock(&sb_i->lock);
  64                 sb_i->lock_owner = current;
  65                 return sb_i->lock_depth++;
  66         }
  67
  68         return sb_i->lock_depth;
  69 }
  70
  71 void reiserfs_write_unlock_once(struct super_block *s, int lock_depth)
  72 {
  73         if (lock_depth == -1)
  74                 reiserfs_write_unlock(s);
  75 }
  76
  77 /*
  78  * Utility function to force a BUG if it is called without the superblock
  79  * write lock held.  caller is the string printed just before calling BUG()
  80  */
  81 void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
  82 {
  83         struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
  84
  85         if (sb_i->lock_depth < 0)
  86                 reiserfs_panic(sb, "%s called without kernel lock held %d",
  87                                caller);
  88 }
  89
  90 #ifdef CONFIG_REISERFS_CHECK
  91 void reiserfs_lock_check_recursive(struct super_block *sb)
  92 {
  93         struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
  94
  95         WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
  96 }
  97 #endif