ocfs2: Add new cluster lock type

Replace the dentry vote mechanism with a cluster lock which covers a set
of dentries. This allows us to force d_delete() only on nodes which actually
care about an unlink.

Every node that does a ->lookup() gets a read only lock on the dentry, until
an unlink during which the unlinking node, will request an exclusive lock,
forcing the other nodes who care about that dentry to d_delete() it. The
effect is that we retain a very lightweight ->d_revalidate(), and at the
same time get to make large improvements to the average case performance of
the ocfs2 unlink and rename operations.

This patch adds the cluster lock type which OCFS2 can attach to
dentries.  A small number of fs/ocfs2/dcache.c functions are stubbed
out so that this change can compile.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/fs/ocfs2/ocfs2_lockid.h b/fs/ocfs2/ocfs2_lockid.h
index 7dd9e1e705b0..4d5d5655c185 100644
--- a/fs/ocfs2/ocfs2_lockid.h
+++ b/fs/ocfs2/ocfs2_lockid.h
@@ -35,12 +35,15 @@
 #define OCFS2_LOCK_ID_MAX_LEN  32
 #define OCFS2_LOCK_ID_PAD "000000"
 
+#define OCFS2_DENTRY_LOCK_INO_START 18
+
 enum ocfs2_lock_type {
         OCFS2_LOCK_TYPE_META = 0,
         OCFS2_LOCK_TYPE_DATA,
         OCFS2_LOCK_TYPE_SUPER,
         OCFS2_LOCK_TYPE_RENAME,
         OCFS2_LOCK_TYPE_RW,
+        OCFS2_LOCK_TYPE_DENTRY,
         OCFS2_NUM_LOCK_TYPES
 };
 
@@ -63,6 +66,9 @@ static inline char ocfs2_lock_type_char(enum ocfs2_lock_type type)
                 case OCFS2_LOCK_TYPE_RW:
                         c = 'W';
                         break;
+                case OCFS2_LOCK_TYPE_DENTRY:
+                        c = 'N';
+                        break;
                 default:
                         c = '\0';
         }
@@ -70,4 +76,23 @@ static inline char ocfs2_lock_type_char(enum ocfs2_lock_type type)
         return c;
 }
 
+static char *ocfs2_lock_type_strings[] = {
+        [OCFS2_LOCK_TYPE_META] = "Meta",
+        [OCFS2_LOCK_TYPE_DATA] = "Data",
+        [OCFS2_LOCK_TYPE_SUPER] = "Super",
+        [OCFS2_LOCK_TYPE_RENAME] = "Rename",
+        /* Need to differntiate from [R]ename.. serializing writes is the
+         * important job it does, anyway. */
+        [OCFS2_LOCK_TYPE_RW] = "Write/Read",
+        [OCFS2_LOCK_TYPE_DENTRY] = "Dentry",
+};
+
+static inline const char *ocfs2_lock_type_string(enum ocfs2_lock_type type)
+{
+#ifdef __KERNEL__
+        mlog_bug_on_msg(type >= OCFS2_NUM_LOCK_TYPES, "%d\n", type);
+#endif
+        return ocfs2_lock_type_strings[type];
+}
+
 #endif  /* OCFS2_LOCKID_H */