lock.c

Go to the documentation of this file.

#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);
    }
}

/*
 * If we already own the lock, just exit and don't increase the depth.
 * Useful when we don't want to lock more than once.
 *
 * We always return the lock_depth we had before calling
 * this function.
 */
int reiserfs_write_lock_once(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;
        return sb_i->lock_depth++;
    }

    return sb_i->lock_depth;
}

void reiserfs_write_unlock_once(struct super_block *s, int lock_depth)
{
    if (lock_depth == -1)
        reiserfs_write_unlock(s);
}

/*
 * 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);

    if (sb_i->lock_depth < 0)
        reiserfs_panic(sb, "%s called without kernel lock held %d",
                   caller);
}

#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