3 files changed, 134 insertions, 3 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index af929eca5412..9ff5811345a9 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -248,6 +248,7 @@ struct ocfs2_super
         struct ocfs2_alloc_stats alloc_stats;
         char dev_str[20];               /* "major,minor" of the device */
 
+        char osb_cluster_stack[OCFS2_STACK_LABEL_LEN + 1];
         struct ocfs2_cluster_connection *cconn;
         struct ocfs2_lock_res osb_super_lockres;
         struct ocfs2_lock_res osb_rename_lockres;
@@ -368,6 +369,12 @@ static inline int ocfs2_is_soft_readonly(struct ocfs2_super *osb)
         return ret;
 }
 
+static inline int ocfs2_userspace_stack(struct ocfs2_super *osb)
+{
+        return (osb->s_feature_incompat &
+                OCFS2_FEATURE_INCOMPAT_USERSPACE_STACK);
+}
+
 static inline int ocfs2_mount_local(struct ocfs2_super *osb)
 {
         return (osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT);
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index c49502329ab0..52c426665154 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -89,7 +89,8 @@
 #define OCFS2_FEATURE_INCOMPAT_SUPP     (OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT \
                                          | OCFS2_FEATURE_INCOMPAT_SPARSE_ALLOC \
                                          | OCFS2_FEATURE_INCOMPAT_INLINE_DATA \
-                                         | OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP)
+                                         | OCFS2_FEATURE_INCOMPAT_EXTENDED_SLOT_MAP \
+                                         | OCFS2_FEATURE_INCOMPAT_USERSPACE_STACK)
 #define OCFS2_FEATURE_RO_COMPAT_SUPP    OCFS2_FEATURE_RO_COMPAT_UNWRITTEN
 
 /*
@@ -131,6 +132,17 @@
 
 
 /*
+ * Support for alternate, userspace cluster stacks.  If set, the superblock
+ * field s_cluster_info contains a tag for the alternate stack in use as
+ * well as the name of the cluster being joined.
+ * mount.ocfs2 must pass in a matching stack name.
+ *
+ * If not set, the classic stack will be used.  This is compatbile with
+ * all older versions.
+ */
+#define OCFS2_FEATURE_INCOMPAT_USERSPACE_STACK  0x0080
+
+/*
  * backup superblock flag is used to indicate that this volume
  * has backup superblocks.
  */
@@ -272,6 +284,10 @@ struct ocfs2_new_group_input {
 #define OCFS2_VOL_UUID_LEN              16
 #define OCFS2_MAX_VOL_LABEL_LEN         64
 
+/* The alternate, userspace stack fields */
+#define OCFS2_STACK_LABEL_LEN           4
+#define OCFS2_CLUSTER_NAME_LEN          16
+
 /* Journal limits (in bytes) */
 #define OCFS2_MIN_JOURNAL_SIZE          (4 * 1024 * 1024)
 
@@ -513,6 +529,13 @@ struct ocfs2_slot_map_extended {
  */
 };
 
+struct ocfs2_cluster_info {
+/*00*/  __u8   ci_stack[OCFS2_STACK_LABEL_LEN];
+        __le32 ci_reserved;
+/*08*/  __u8   ci_cluster[OCFS2_CLUSTER_NAME_LEN];
+/*18*/
+};
+
 /*
  * On disk superblock for OCFS2
  * Note that it is contained inside an ocfs2_dinode, so all offsets
@@ -545,7 +568,20 @@ 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*/
+/*A0*/  struct ocfs2_cluster_info s_cluster_info; /* Selected userspace
+                                                     stack.  Only valid
+                                                     with INCOMPAT flag. */
+/*B8*/  __le64 s_reserved2[17];         /* Fill out superblock */
+/*140*/
+
+        /*
+         * NOTE: As stated above, all offsets are relative to
+         * ocfs2_dinode.id2, which is at 0xC0 in the inode.
+         * 0xC0 + 0x140 = 0x200 or 512 bytes.  A superblock must fit within
+         * our smallest blocksize, which is 512 bytes.  To ensure this,
+         * we reserve the space in s_reserved2.  Anything past s_reserved2
+         * will not be available on the smallest blocksize.
+         */
 };
 
 /*
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index e27a0d47ea2b..96ebe36d5d77 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -87,6 +87,7 @@ struct mount_options
         unsigned int    atime_quantum;
         signed short    slot;
         unsigned int    localalloc_opt;
+        char            cluster_stack[OCFS2_STACK_LABEL_LEN + 1];
 };
 
 static int ocfs2_parse_options(struct super_block *sb, char *options,
@@ -152,6 +153,7 @@ enum {
         Opt_commit,
         Opt_localalloc,
         Opt_localflocks,
+        Opt_stack,
         Opt_err,
 };
 
@@ -170,6 +172,7 @@ static match_table_t tokens = {
         {Opt_commit, "commit=%u"},
         {Opt_localalloc, "localalloc=%d"},
         {Opt_localflocks, "localflocks"},
+        {Opt_stack, "cluster_stack=%s"},
         {Opt_err, NULL}
 };
 
@@ -549,8 +552,17 @@ static int ocfs2_verify_heartbeat(struct ocfs2_super *osb)
                 }
         }
 
+        if (ocfs2_userspace_stack(osb)) {
+                if (osb->s_mount_opt & OCFS2_MOUNT_HB_LOCAL) {
+                        mlog(ML_ERROR, "Userspace stack expected, but "
+                             "o2cb heartbeat arguments passed to mount\n");
+                        return -EINVAL;
+                }
+        }
+
         if (!(osb->s_mount_opt & OCFS2_MOUNT_HB_LOCAL)) {
-                if (!ocfs2_mount_local(osb) && !ocfs2_is_hard_readonly(osb)) {
+                if (!ocfs2_mount_local(osb) && !ocfs2_is_hard_readonly(osb) &&
+                    !ocfs2_userspace_stack(osb)) {
                         mlog(ML_ERROR, "Heartbeat has to be started to mount "
                              "a read-write clustered device.\n");
                         return -EINVAL;
@@ -560,6 +572,35 @@ static int ocfs2_verify_heartbeat(struct ocfs2_super *osb)
         return 0;
 }
 
+/*
+ * If we're using a userspace stack, mount should have passed
+ * a name that matches the disk.  If not, mount should not
+ * have passed a stack.
+ */
+static int ocfs2_verify_userspace_stack(struct ocfs2_super *osb,
+                                        struct mount_options *mopt)
+{
+        if (!ocfs2_userspace_stack(osb) && mopt->cluster_stack[0]) {
+                mlog(ML_ERROR,
+                     "cluster stack passed to mount, but this filesystem "
+                     "does not support it\n");
+                return -EINVAL;
+        }
+
+        if (ocfs2_userspace_stack(osb) &&
+            strncmp(osb->osb_cluster_stack, mopt->cluster_stack,
+                    OCFS2_STACK_LABEL_LEN)) {
+                mlog(ML_ERROR,
+                     "cluster stack passed to mount (\"%s\") does not "
+                     "match the filesystem (\"%s\")\n",
+                     mopt->cluster_stack,
+                     osb->osb_cluster_stack);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
 static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
 {
         struct dentry *root;
@@ -598,6 +639,10 @@ static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
         osb->osb_commit_interval = parsed_options.commit_interval;
         osb->local_alloc_size = parsed_options.localalloc_opt;
 
+        status = ocfs2_verify_userspace_stack(osb, &parsed_options);
+        if (status)
+                goto read_super_error;
+
         sb->s_magic = OCFS2_SUPER_MAGIC;
 
         /* Hard readonly mode only if: bdev_read_only, MS_RDONLY,
@@ -752,6 +797,7 @@ static int ocfs2_parse_options(struct super_block *sb,
         mopt->atime_quantum = OCFS2_DEFAULT_ATIME_QUANTUM;
         mopt->slot = OCFS2_INVALID_SLOT;
         mopt->localalloc_opt = OCFS2_DEFAULT_LOCAL_ALLOC_SIZE;
+        mopt->cluster_stack[0] = '\0';
 
         if (!options) {
                 status = 1;
@@ -853,6 +899,25 @@ static int ocfs2_parse_options(struct super_block *sb,
                         if (!is_remount)
                                 mopt->mount_opt |= OCFS2_MOUNT_LOCALFLOCKS;
                         break;
+                case Opt_stack:
+                        /* Check both that the option we were passed
+                         * is of the right length and that it is a proper
+                         * string of the right length.
+                         */
+                        if (((args[0].to - args[0].from) !=
+                             OCFS2_STACK_LABEL_LEN) ||
+                            (strnlen(args[0].from,
+                                     OCFS2_STACK_LABEL_LEN) !=
+                             OCFS2_STACK_LABEL_LEN)) {
+                                mlog(ML_ERROR,
+                                     "Invalid cluster_stack option\n");
+                                status = 0;
+                                goto bail;
+                        }
+                        memcpy(mopt->cluster_stack, args[0].from,
+                               OCFS2_STACK_LABEL_LEN);
+                        mopt->cluster_stack[OCFS2_STACK_LABEL_LEN] = '\0';
+                        break;
                 default:
                         mlog(ML_ERROR,
                              "Unrecognized mount option \"%s\" "
@@ -911,6 +976,10 @@ static int ocfs2_show_options(struct seq_file *s, struct vfsmount *mnt)
         if (opts & OCFS2_MOUNT_LOCALFLOCKS)
                 seq_printf(s, ",localflocks,");
 
+        if (osb->osb_cluster_stack[0])
+                seq_printf(s, ",cluster_stack=%.*s", OCFS2_STACK_LABEL_LEN,
+                           osb->osb_cluster_stack);
+
         return 0;
 }
 
@@ -1403,6 +1472,25 @@ static int ocfs2_initialize_super(struct super_block *sb,
                 goto bail;
         }
 
+        if (ocfs2_userspace_stack(osb)) {
+                memcpy(osb->osb_cluster_stack,
+                       OCFS2_RAW_SB(di)->s_cluster_info.ci_stack,
+                       OCFS2_STACK_LABEL_LEN);
+                osb->osb_cluster_stack[OCFS2_STACK_LABEL_LEN] = '\0';
+                if (strlen(osb->osb_cluster_stack) != OCFS2_STACK_LABEL_LEN) {
+                        mlog(ML_ERROR,
+                             "couldn't mount because of an invalid "
+                             "cluster stack label (%s) \n",
+                             osb->osb_cluster_stack);
+                        status = -EINVAL;
+                        goto bail;
+                }
+        } else {
+                /* The empty string is identical with classic tools that
+                 * don't know about s_cluster_info. */
+                osb->osb_cluster_stack[0] = '\0';
+        }
+
         get_random_bytes(&osb->s_next_generation, sizeof(u32));
 
         /* FIXME