278f6679f4
The reiserfs write lock replaced the BKL and uses similar semantics. Frederic's locking code makes a distinction between when the lock is nested and when it's being acquired/released, but I don't think that's the right distinction to make. The right distinction is between the lock being released at end-of-use and the lock being released for a schedule. The unlock should return the depth and the lock should restore it, rather than the other way around as it is now. This patch implements that and adds a number of places where the lock should be dropped. Signed-off-by: Jeff Mahoney <jeffm@suse.com>
101 lines
2.6 KiB
C
101 lines
2.6 KiB
C
#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
|