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>

3 files changed, 133 insertions, 15 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 95f783dbe8b2..f78e9ed53249 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -374,6 +374,13 @@ static inline int ocfs2_mount_local(struct ocfs2_super *osb)
         return (osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT);
 }
 
+static inline int ocfs2_uses_extended_slot_map(struct ocfs2_super *osb)
+{
+        return (osb->s_feature_incompat &
+                OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP);
+}
+
+
 #define OCFS2_IS_VALID_DINODE(ptr)                                      \
         (!strcmp((ptr)->i_signature, OCFS2_INODE_SIGNATURE))
 
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index 3299116b8021..c49502329ab0 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 @@ struct ocfs2_extent_block
 
 /*
  * 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_slot_map {
  */
 };
 
+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
diff --git a/fs/ocfs2/slot_map.c b/fs/ocfs2/slot_map.c
index e7e7a74156b1..63fb1b26d964 100644
--- a/fs/ocfs2/slot_map.c
+++ b/fs/ocfs2/slot_map.c
@@ -49,6 +49,8 @@ struct ocfs2_slot {
 };
 
 struct ocfs2_slot_info {
+        int si_extended;
+        int si_slots_per_block;
         struct inode *si_inode;
         unsigned int si_blocks;
         struct buffer_head **si_bh;
@@ -78,17 +80,37 @@ static void ocfs2_set_slot(struct ocfs2_slot_info *si,
         si->si_slots[slot_num].sl_node_num = node_num;
 }
 
+/* This version is for the extended slot map */
+static void ocfs2_update_slot_info_extended(struct ocfs2_slot_info *si)
+{
+        int b, i, slotno;
+        struct ocfs2_slot_map_extended *se;
+
+        slotno = 0;
+        for (b = 0; b < si->si_blocks; b++) {
+                se = (struct ocfs2_slot_map_extended *)si->si_bh[b]->b_data;
+                for (i = 0;
+                     (i < si->si_slots_per_block) &&
+                     (slotno < si->si_num_slots);
+                     i++, slotno++) {
+                        if (se->se_slots[i].es_valid)
+                                ocfs2_set_slot(si, slotno,
+                                               le32_to_cpu(se->se_slots[i].es_node_num));
+                        else
+                                ocfs2_invalidate_slot(si, slotno);
+                }
+        }
+}
+
 /*
  * Post the slot information on disk into our slot_info struct.
  * Must be protected by osb_lock.
  */
-static void ocfs2_update_slot_info(struct ocfs2_slot_info *si)
+static void ocfs2_update_slot_info_old(struct ocfs2_slot_info *si)
 {
         int i;
         struct ocfs2_slot_map *sm;
 
-        /* we don't read the slot block here as ocfs2_super_lock
-         * should've made sure we have the most recent copy. */
         sm = (struct ocfs2_slot_map *)si->si_bh[0]->b_data;
 
         for (i = 0; i < si->si_num_slots; i++) {
@@ -99,6 +121,18 @@ static void ocfs2_update_slot_info(struct ocfs2_slot_info *si)
         }
 }
 
+static void ocfs2_update_slot_info(struct ocfs2_slot_info *si)
+{
+        /*
+         * The slot data will have been refreshed when ocfs2_super_lock
+         * was taken.
+         */
+        if (si->si_extended)
+                ocfs2_update_slot_info_extended(si);
+        else
+                ocfs2_update_slot_info_old(si);
+}
+
 int ocfs2_refresh_slot_info(struct ocfs2_super *osb)
 {
         int ret;
@@ -131,13 +165,31 @@ int ocfs2_refresh_slot_info(struct ocfs2_super *osb)
 
 /* post the our slot info stuff into it's destination bh and write it
  * out. */
-static int ocfs2_update_disk_slots(struct ocfs2_super *osb,
-                                   struct ocfs2_slot_info *si)
+static void ocfs2_update_disk_slot_extended(struct ocfs2_slot_info *si,
+                                            int slot_num,
+                                            struct buffer_head **bh)
+{
+        int blkind = slot_num / si->si_slots_per_block;
+        int slotno = slot_num % si->si_slots_per_block;
+        struct ocfs2_slot_map_extended *se;
+
+        BUG_ON(blkind >= si->si_blocks);
+
+        se = (struct ocfs2_slot_map_extended *)si->si_bh[blkind]->b_data;
+        se->se_slots[slotno].es_valid = si->si_slots[slot_num].sl_valid;
+        if (si->si_slots[slot_num].sl_valid)
+                se->se_slots[slotno].es_node_num =
+                        cpu_to_le32(si->si_slots[slot_num].sl_node_num);
+        *bh = si->si_bh[blkind];
+}
+
+static void ocfs2_update_disk_slot_old(struct ocfs2_slot_info *si,
+                                       int slot_num,
+                                       struct buffer_head **bh)
 {
-        int status, i;
+        int i;
         struct ocfs2_slot_map *sm;
 
-        spin_lock(&osb->osb_lock);
         sm = (struct ocfs2_slot_map *)si->si_bh[0]->b_data;
         for (i = 0; i < si->si_num_slots; i++) {
                 if (si->si_slots[i].sl_valid)
@@ -146,9 +198,24 @@ static int ocfs2_update_disk_slots(struct ocfs2_super *osb,
                 else
                         sm->sm_slots[i] = cpu_to_le16(OCFS2_INVALID_SLOT);
         }
+        *bh = si->si_bh[0];
+}
+
+static int ocfs2_update_disk_slot(struct ocfs2_super *osb,
+                                  struct ocfs2_slot_info *si,
+                                  int slot_num)
+{
+        int status;
+        struct buffer_head *bh;
+
+        spin_lock(&osb->osb_lock);
+        if (si->si_extended)
+                ocfs2_update_disk_slot_extended(si, slot_num, &bh);
+        else
+                ocfs2_update_disk_slot_old(si, slot_num, &bh);
         spin_unlock(&osb->osb_lock);
 
-        status = ocfs2_write_block(osb, si->si_bh[0], si->si_inode);
+        status = ocfs2_write_block(osb, bh, si->si_inode);
         if (status < 0)
                 mlog_errno(status);
 
@@ -165,7 +232,12 @@ static int ocfs2_slot_map_physical_size(struct ocfs2_super *osb,
 {
         unsigned long long bytes_needed;
 
-        bytes_needed = osb->max_slots * sizeof(__le16);
+        if (ocfs2_uses_extended_slot_map(osb)) {
+                bytes_needed = osb->max_slots *
+                        sizeof(struct ocfs2_extended_slot);
+        } else {
+                bytes_needed = osb->max_slots * sizeof(__le16);
+        }
         if (bytes_needed > i_size_read(inode)) {
                 mlog(ML_ERROR,
                      "Slot map file is too small!  (size %llu, needed %llu)\n",
@@ -279,7 +351,7 @@ int ocfs2_clear_slot(struct ocfs2_super *osb, int slot_num)
         ocfs2_invalidate_slot(si, slot_num);
         spin_unlock(&osb->osb_lock);
 
-        return ocfs2_update_disk_slots(osb, osb->slot_info);
+        return ocfs2_update_disk_slot(osb, osb->slot_info, slot_num);
 }
 
 static int ocfs2_map_slot_buffers(struct ocfs2_super *osb,
@@ -301,6 +373,16 @@ static int ocfs2_map_slot_buffers(struct ocfs2_super *osb,
         if (!si->si_blocks)
                 goto bail;
 
+        if (si->si_extended)
+                si->si_slots_per_block =
+                        (osb->sb->s_blocksize /
+                         sizeof(struct ocfs2_extended_slot));
+        else
+                si->si_slots_per_block = osb->sb->s_blocksize / sizeof(__le16);
+
+        /* The size checks above should ensure this */
+        BUG_ON((osb->max_slots / si->si_slots_per_block) > blocks);
+
         mlog(0, "Slot map needs %u buffers for %llu bytes\n",
              si->si_blocks, bytes);
 
@@ -352,6 +434,7 @@ int ocfs2_init_slot_info(struct ocfs2_super *osb)
                 goto bail;
         }
 
+        si->si_extended = ocfs2_uses_extended_slot_map(osb);
         si->si_num_slots = osb->max_slots;
         si->si_slots = (struct ocfs2_slot *)((char *)si +
                                              sizeof(struct ocfs2_slot_info));
@@ -425,7 +508,7 @@ int ocfs2_find_slot(struct ocfs2_super *osb)
 
         mlog(0, "taking node slot %d\n", osb->slot_num);
 
-        status = ocfs2_update_disk_slots(osb, si);
+        status = ocfs2_update_disk_slot(osb, si, osb->slot_num);
         if (status < 0)
                 mlog_errno(status);
 
@@ -436,7 +519,7 @@ bail:
 
 void ocfs2_put_slot(struct ocfs2_super *osb)
 {
-        int status;
+        int status, slot_num;
         struct ocfs2_slot_info *si = osb->slot_info;
 
         if (!si)
@@ -445,11 +528,12 @@ void ocfs2_put_slot(struct ocfs2_super *osb)
         spin_lock(&osb->osb_lock);
         ocfs2_update_slot_info(si);
 
+        slot_num = osb->slot_num;
         ocfs2_invalidate_slot(si, osb->slot_num);
         osb->slot_num = OCFS2_INVALID_SLOT;
         spin_unlock(&osb->osb_lock);
 
-        status = ocfs2_update_disk_slots(osb, si);
+        status = ocfs2_update_disk_slot(osb, si, slot_num);
         if (status < 0) {
                 mlog_errno(status);
                 goto bail;