ocfs2: New slot map format
The old slot map had a few limitations:
- It was limited to one block, so the maximum slot count was 255.
- Each slot was signed 16bits, limiting node numbers to INT16_MAX.
- An empty slot was marked by the magic 0xFFFF (-1).
The new slot map format provides 32bit node numbers (UINT32_MAX), a
separate space to mark a slot in use, and extra room to grow. The slot
map is now bounded by i_size, not a block.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index 3299116..c495023 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -88,7 +88,8 @@
#define OCFS2_FEATURE_COMPAT_SUPP OCFS2_FEATURE_COMPAT_BACKUP_SB
#define OCFS2_FEATURE_INCOMPAT_SUPP (OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT \
| OCFS2_FEATURE_INCOMPAT_SPARSE_ALLOC \
- | OCFS2_FEATURE_INCOMPAT_INLINE_DATA)
+ | OCFS2_FEATURE_INCOMPAT_INLINE_DATA \
+ | OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP)
#define OCFS2_FEATURE_RO_COMPAT_SUPP OCFS2_FEATURE_RO_COMPAT_UNWRITTEN
/*
@@ -125,6 +126,10 @@
/* Support for data packed into inode blocks */
#define OCFS2_FEATURE_INCOMPAT_INLINE_DATA 0x0040
+/* Support for the extended slot map */
+#define OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP 0x100
+
+
/*
* backup superblock flag is used to indicate that this volume
* has backup superblocks.
@@ -476,7 +481,8 @@
/*
* On disk slot map for OCFS2. This defines the contents of the "slot_map"
- * system file.
+ * system file. A slot is valid if it contains a node number >= 0. The
+ * value -1 (0xFFFF) is OCFS2_INVALID_SLOT. This marks a slot empty.
*/
struct ocfs2_slot_map {
/*00*/ __le16 sm_slots[0];
@@ -486,6 +492,27 @@
*/
};
+struct ocfs2_extended_slot {
+/*00*/ __u8 es_valid;
+ __u8 es_reserved1[3];
+ __le32 es_node_num;
+/*10*/
+};
+
+/*
+ * The extended slot map, used when OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP
+ * is set. It separates out the valid marker from the node number, and
+ * has room to grow. Unlike the old slot map, this format is defined by
+ * i_size.
+ */
+struct ocfs2_slot_map_extended {
+/*00*/ struct ocfs2_extended_slot se_slots[0];
+/*
+ * Actual size is i_size of the slot_map system file. It should
+ * match s_max_slots * sizeof(struct ocfs2_extended_slot)
+ */
+};
+
/*
* On disk superblock for OCFS2
* Note that it is contained inside an ocfs2_dinode, so all offsets