Fixed MTP to work with TWRP

fs/reiserfs/lock.c

@@ -0,0 +1,100 @@
+#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