[PATCH V2 1/3] dcache: add a new enum type for 'dentry_d_lock_class'

[yu kuai]

'dentry_d_lock_class' can be used for spin_lock_nested in case lockdep
confused about two different dentry take the 'd_lock'.

However, a single 'DENTRY_D_LOCK_NESTED' may not be enough if more than
two dentry are involed. So, add in 'DENTRY_D_LOCK_NESTED_TWICE'.

Signed-off-by: yu kuai <yukuai3@xxxxxxxxxx>
---
 include/linux/dcache.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 10090f11ab95..830405b401ce 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -129,7 +129,16 @@ struct dentry {
 enum dentry_d_lock_class
 {
 	DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
-	DENTRY_D_LOCK_NESTED
+	/* 
+	 * used by spin_lock_nested when two d_lock need to be taken
+	 * at the same time
+	 */
+	DENTRY_D_LOCK_NESTED,
+	/*
+	 * used by spin_lock_nested when three d_lock need to be taken
+	 * at the same time
+	 */
+	DENTRY_D_LOCK_NESTED_TWICE
 };
 
 struct dentry_operations {
-- 
2.17.2