1 files changed, 88 insertions, 0 deletions

diff --git a/fs/reiserfs/lock.c b/fs/reiserfs/lock.c
new file mode 100644
index 000000000000..ee2cfc0fd8a7
--- /dev/null
+++ b/fs/reiserfs/lock.c
@@ -0,0 +1,88 @@
+#include <linux/reiserfs_fs.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 partialy 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);
+}