ocfs2: Add an incompat feature flag OCFS2_FEATURE_INCOMPAT_CLUSTERINFO

OCFS2_FEATURE_INCOMPAT_CLUSTERINFO allows us to use sb->s_cluster_info for
both userspace and o2cb cluster stacks. It also allows us to extend cluster
info to include stack flags.

This patch also adds stackflags to sb->s_clusterinfo. It also introduces a
clusterinfo flag OCFS2_CLUSTER_O2CB_GLOBAL_HEARTBEAT to denote the enabled
global heartbeat mode.

This incompat flag can be set/cleared using tunefs.ocfs2 --fs-features. The
clusterinfo flag is set/cleared using tunefs.ocfs2 --update-cluster-stack.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>

3 files changed, 66 insertions, 9 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index c67003b6b5a..d5496a792bd 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -368,6 +368,8 @@ struct ocfs2_super
         struct ocfs2_alloc_stats alloc_stats;
         char dev_str[20];               /* "major,minor" of the device */
 
+        u8 osb_stackflags;
+
         char osb_cluster_stack[OCFS2_STACK_LABEL_LEN + 1];
         struct ocfs2_cluster_connection *cconn;
         struct ocfs2_lock_res osb_super_lockres;
@@ -601,10 +603,35 @@ static inline int ocfs2_is_soft_readonly(struct ocfs2_super *osb)
         return ret;
 }
 
-static inline int ocfs2_userspace_stack(struct ocfs2_super *osb)
+static inline int ocfs2_clusterinfo_valid(struct ocfs2_super *osb)
 {
         return (osb->s_feature_incompat &
-                OCFS2_FEATURE_INCOMPAT_USERSPACE_STACK);
+                (OCFS2_FEATURE_INCOMPAT_USERSPACE_STACK |
+                 OCFS2_FEATURE_INCOMPAT_CLUSTERINFO));
+}
+
+static inline int ocfs2_userspace_stack(struct ocfs2_super *osb)
+{
+        if (ocfs2_clusterinfo_valid(osb) &&
+            memcmp(osb->osb_cluster_stack, OCFS2_CLASSIC_CLUSTER_STACK,
+                   OCFS2_STACK_LABEL_LEN))
+                return 1;
+        return 0;
+}
+
+static inline int ocfs2_o2cb_stack(struct ocfs2_super *osb)
+{
+        if (ocfs2_clusterinfo_valid(osb) &&
+            !memcmp(osb->osb_cluster_stack, OCFS2_CLASSIC_CLUSTER_STACK,
+                   OCFS2_STACK_LABEL_LEN))
+                return 1;
+        return 0;
+}
+
+static inline int ocfs2_cluster_o2cb_global_heartbeat(struct ocfs2_super *osb)
+{
+        return ocfs2_o2cb_stack(osb) &&
+                (osb->osb_stackflags & OCFS2_CLUSTER_O2CB_GLOBAL_HEARTBEAT);
 }
 
 static inline int ocfs2_mount_local(struct ocfs2_super *osb)
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index fa31d05e41b..d5b1d99abc3 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -101,7 +101,8 @@
                                          | OCFS2_FEATURE_INCOMPAT_META_ECC \
                                          | OCFS2_FEATURE_INCOMPAT_INDEXED_DIRS \
                                          | OCFS2_FEATURE_INCOMPAT_REFCOUNT_TREE \
-                                         | OCFS2_FEATURE_INCOMPAT_DISCONTIG_BG)
+                                         | OCFS2_FEATURE_INCOMPAT_DISCONTIG_BG  \
+                                         | OCFS2_FEATURE_INCOMPAT_CLUSTERINFO)
 #define OCFS2_FEATURE_RO_COMPAT_SUPP    (OCFS2_FEATURE_RO_COMPAT_UNWRITTEN \
                                          | OCFS2_FEATURE_RO_COMPAT_USRQUOTA \
                                          | OCFS2_FEATURE_RO_COMPAT_GRPQUOTA)
@@ -170,6 +171,13 @@
 #define OCFS2_FEATURE_INCOMPAT_DISCONTIG_BG     0x2000
 
 /*
+ * Incompat bit to indicate useable clusterinfo with stackflags for all
+ * cluster stacks (userspace adnd o2cb). If this bit is set,
+ * INCOMPAT_USERSPACE_STACK becomes superfluous and thus should not be set.
+ */
+#define OCFS2_FEATURE_INCOMPAT_CLUSTERINFO      0x4000
+
+/*
  * backup superblock flag is used to indicate that this volume
  * has backup superblocks.
  */
@@ -292,10 +300,13 @@
 #define OCFS2_VOL_UUID_LEN              16
 #define OCFS2_MAX_VOL_LABEL_LEN         64
 
-/* The alternate, userspace stack fields */
+/* The cluster stack fields */
 #define OCFS2_STACK_LABEL_LEN           4
 #define OCFS2_CLUSTER_NAME_LEN          16
 
+/* Classic (historically speaking) cluster stack */
+#define OCFS2_CLASSIC_CLUSTER_STACK     "o2cb"
+
 /* Journal limits (in bytes) */
 #define OCFS2_MIN_JOURNAL_SIZE          (4 * 1024 * 1024)
 
@@ -305,6 +316,11 @@
  */
 #define OCFS2_MIN_XATTR_INLINE_SIZE     256
 
+/*
+ * Cluster info flags (ocfs2_cluster_info.ci_stackflags)
+ */
+#define OCFS2_CLUSTER_O2CB_GLOBAL_HEARTBEAT     (0x01)
+
 struct ocfs2_system_inode_info {
         char    *si_name;
         int     si_iflags;
@@ -566,9 +582,21 @@ struct ocfs2_slot_map_extended {
  */
 };
 
+/*
+ * ci_stackflags is only valid if the incompat bit
+ * OCFS2_FEATURE_INCOMPAT_CLUSTERINFO is set.
+ */
 struct ocfs2_cluster_info {
 /*00*/  __u8   ci_stack[OCFS2_STACK_LABEL_LEN];
-        __le32 ci_reserved;
+        union {
+                __le32 ci_reserved;
+                struct {
+                        __u8 ci_stackflags;
+                        __u8 ci_reserved1;
+                        __u8 ci_reserved2;
+                        __u8 ci_reserved3;
+                };
+        };
 /*08*/  __u8   ci_cluster[OCFS2_CLUSTER_NAME_LEN];
 /*18*/
 };
@@ -605,9 +633,9 @@ struct ocfs2_super_block {
                                          * group header */
 /*50*/  __u8  s_label[OCFS2_MAX_VOL_LABEL_LEN]; /* Label for mounting, etc. */
 /*90*/  __u8  s_uuid[OCFS2_VOL_UUID_LEN];       /* 128-bit uuid */
-/*A0*/  struct ocfs2_cluster_info s_cluster_info; /* Selected userspace
-                                                     stack.  Only valid
-                                                     with INCOMPAT flag. */
+/*A0*/  struct ocfs2_cluster_info s_cluster_info; /* Only valid if either
+                                                     userspace or clusterinfo
+                                                     INCOMPAT flag set. */
 /*B8*/  __le16 s_xattr_inline_size;     /* extended attribute inline size
                                            for this fs*/
         __le16 s_reserved0;
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index fa1be1b304d..75543173939 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -2149,7 +2149,9 @@ static int ocfs2_initialize_super(struct super_block *sb,
                 goto bail;
         }
 
-        if (ocfs2_userspace_stack(osb)) {
+        if (ocfs2_clusterinfo_valid(osb)) {
+                osb->osb_stackflags =
+                        OCFS2_RAW_SB(di)->s_cluster_info.ci_stackflags;
                 memcpy(osb->osb_cluster_stack,
                        OCFS2_RAW_SB(di)->s_cluster_info.ci_stack,
                        OCFS2_STACK_LABEL_LEN);