lock.c
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#include "reiserfs.h"
#include <linux/mutex.h>
/*
* The previous reiserfs locking scheme was heavily based on
* the tricky properties of the Bkl:
*
* - it was acquired recursively by a same task
* - the performances relied on the release-while-schedule() property
*
* Now that we replace it by a mutex, we still want to keep the same
* recursive property to avoid big changes in the code structure.
* We use our own lock_owner here because the owner field on a mutex
* is only available in SMP or mutex debugging, also we only need this field
* for this mutex, no need for a system wide mutex facility.
*
* Also this lock is often released before a call that could block because
* reiserfs performances were partially based on the release while schedule()
* property of the Bkl.
*/
void reiserfs_write_lock(struct super_block *s)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
if (sb_i->lock_owner != current) {
mutex_lock(&sb_i->lock);
sb_i->lock_owner = current;
}
/* No need to protect it, only the current task touches it */
sb_i->lock_depth++;
}
void reiserfs_write_unlock(struct super_block *s)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
/*
* Are we unlocking without even holding the lock?
* Such a situation must raise a BUG() if we don't want
* to corrupt the data.
*/
BUG_ON(sb_i->lock_owner != current);
if (--sb_i->lock_depth == -1) {
sb_i->lock_owner = NULL;
mutex_unlock(&sb_i->lock);
}
}
int __must_check reiserfs_write_unlock_nested(struct super_block *s)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
int depth;
/* this can happen when the lock isn't always held */
if (sb_i->lock_owner != current)
return -1;
depth = sb_i->lock_depth;
sb_i->lock_depth = -1;
sb_i->lock_owner = NULL;
mutex_unlock(&sb_i->lock);
return depth;
}
void reiserfs_write_lock_nested(struct super_block *s, int depth)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(s);
/* this can happen when the lock isn't always held */
if (depth == -1)
return;
mutex_lock(&sb_i->lock);
sb_i->lock_owner = current;
sb_i->lock_depth = depth;
}
/*
* Utility function to force a BUG if it is called without the superblock
* write lock held. caller is the string printed just before calling BUG()
*/
void reiserfs_check_lock_depth(struct super_block *sb, char *caller)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
WARN_ON(sb_i->lock_depth < 0);
}
#ifdef CONFIG_REISERFS_CHECK
void reiserfs_lock_check_recursive(struct super_block *sb)
{
struct reiserfs_sb_info *sb_i = REISERFS_SB(sb);
WARN_ONCE((sb_i->lock_depth > 0), "Unwanted recursive reiserfs lock!\n");
}
#endif