ocfs2: mount shared volume without ha stack

Usually we create and use a ocfs2 shared volume on the top of ha stack.
For pcmk based ha stack, which includes DLM, corosync and pacemaker
services.

The customers complained they could not mount existent ocfs2 volume in
the single node without ha stack, e.g.  single node backup/restore
scenario.

Like this case, the customers just want to access the data from the
existent ocfs2 volume quickly, but do not want to restart or setup ha
stack.

Then, I'd like to add a mount option "nocluster", if the users use this
option to mount a ocfs2 shared volume, the whole mount will not depend
on the ha related services.  the command will mount the existent ocfs2
volume directly (like local mount), for avoiding setup the ha stack.

Signed-off-by: Gang He <ghe@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Link: http://lkml.kernel.org/r/20200423053300.22661-1-ghe@suse.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Gang He

fs/ocfs2/ocfs2.h

@@ -279,6 +279,7 @@ enum ocfs2_mount_options
 	OCFS2_MOUNT_JOURNAL_ASYNC_COMMIT = 1 << 15,  /* Journal Async Commit */
 	OCFS2_MOUNT_ERRORS_CONT = 1 << 16, /* Return EIO to the calling process on error */
 	OCFS2_MOUNT_ERRORS_ROFS = 1 << 17, /* Change filesystem to read-only on error */
+	OCFS2_MOUNT_NOCLUSTER = 1 << 18, /* No cluster aware filesystem mount */
 };
 
 #define OCFS2_OSB_SOFT_RO	0x0001
@@ -673,7 +674,8 @@ static inline int ocfs2_cluster_o2cb_global_heartbeat(struct ocfs2_super *osb)
 
 static inline int ocfs2_mount_local(struct ocfs2_super *osb)
 {
-	return (osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT);
+	return ((osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT)
+		|| (osb->s_mount_opt & OCFS2_MOUNT_NOCLUSTER));
 }
 
 static inline int ocfs2_uses_extended_slot_map(struct ocfs2_super *osb)

fs/ocfs2/slot_map.c

@@ -254,14 +254,16 @@ static int __ocfs2_find_empty_slot(struct ocfs2_slot_info *si,
 	int i, ret = -ENOSPC;
 
 	if ((preferred >= 0) && (preferred < si->si_num_slots)) {
-		if (!si->si_slots[preferred].sl_valid) {
+		if (!si->si_slots[preferred].sl_valid ||
+		    !si->si_slots[preferred].sl_node_num) {
 			ret = preferred;
 			goto out;
 		}
 	}
 
 	for(i = 0; i < si->si_num_slots; i++) {
-		if (!si->si_slots[i].sl_valid) {
+		if (!si->si_slots[i].sl_valid ||
+		    !si->si_slots[i].sl_node_num) {
 			ret = i;
 			break;
 		}
@@ -456,24 +458,30 @@ int ocfs2_find_slot(struct ocfs2_super *osb)
 	spin_lock(&osb->osb_lock);
 	ocfs2_update_slot_info(si);
 
-	/* search for ourselves first and take the slot if it already
-	 * exists. Perhaps we need to mark this in a variable for our
-	 * own journal recovery? Possibly not, though we certainly
-	 * need to warn to the user */
-	slot = __ocfs2_node_num_to_slot(si, osb->node_num);
-	if (slot < 0) {
-		/* if no slot yet, then just take 1st available
-		 * one. */
-		slot = __ocfs2_find_empty_slot(si, osb->preferred_slot);
+	if (ocfs2_mount_local(osb))
+		/* use slot 0 directly in local mode */
+		slot = 0;
+	else {
+		/* search for ourselves first and take the slot if it already
+		 * exists. Perhaps we need to mark this in a variable for our
+		 * own journal recovery? Possibly not, though we certainly
+		 * need to warn to the user */
+		slot = __ocfs2_node_num_to_slot(si, osb->node_num);
 		if (slot < 0) {
-			spin_unlock(&osb->osb_lock);
-			mlog(ML_ERROR, "no free slots available!\n");
-			status = -EINVAL;
-			goto bail;
-		}
-	} else
-		printk(KERN_INFO "ocfs2: Slot %d on device (%s) was already "
-		       "allocated to this node!\n", slot, osb->dev_str);
+			/* if no slot yet, then just take 1st available
+			 * one. */
+			slot = __ocfs2_find_empty_slot(si, osb->preferred_slot);
+			if (slot < 0) {
+				spin_unlock(&osb->osb_lock);
+				mlog(ML_ERROR, "no free slots available!\n");
+				status = -EINVAL;
+				goto bail;
+			}
+		} else
+			printk(KERN_INFO "ocfs2: Slot %d on device (%s) was "
+			       "already allocated to this node!\n",
+			       slot, osb->dev_str);
+	}
 
 	ocfs2_set_slot(si, slot, osb->node_num);
 	osb->slot_num = slot;

fs/ocfs2/super.c

@@ -175,6 +175,7 @@ enum {
 	Opt_dir_resv_level,
 	Opt_journal_async_commit,
 	Opt_err_cont,
+	Opt_nocluster,
 	Opt_err,
 };
 
@@ -208,6 +209,7 @@ static const match_table_t tokens = {
 	{Opt_dir_resv_level, "dir_resv_level=%u"},
 	{Opt_journal_async_commit, "journal_async_commit"},
 	{Opt_err_cont, "errors=continue"},
+	{Opt_nocluster, "nocluster"},
 	{Opt_err, NULL}
 };
 
@@ -619,6 +621,13 @@ static int ocfs2_remount(struct super_block *sb, int *flags, char *data)
 		goto out;
 	}
 
+	tmp = OCFS2_MOUNT_NOCLUSTER;
+	if ((osb->s_mount_opt & tmp) != (parsed_options.mount_opt & tmp)) {
+		ret = -EINVAL;
+		mlog(ML_ERROR, "Cannot change nocluster option on remount\n");
+		goto out;
+	}
+
 	tmp = OCFS2_MOUNT_HB_LOCAL | OCFS2_MOUNT_HB_GLOBAL |
 		OCFS2_MOUNT_HB_NONE;
 	if ((osb->s_mount_opt & tmp) != (parsed_options.mount_opt & tmp)) {
@@ -859,6 +868,7 @@ static int ocfs2_verify_userspace_stack(struct ocfs2_super *osb,
 	}
 
 	if (ocfs2_userspace_stack(osb) &&
+	    !(osb->s_mount_opt & OCFS2_MOUNT_NOCLUSTER) &&
 	    strncmp(osb->osb_cluster_stack, mopt->cluster_stack,
 		    OCFS2_STACK_LABEL_LEN)) {
 		mlog(ML_ERROR,
@@ -1139,6 +1149,11 @@ static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
 	       osb->s_mount_opt & OCFS2_MOUNT_DATA_WRITEBACK ? "writeback" :
 	       "ordered");
 
+	if ((osb->s_mount_opt & OCFS2_MOUNT_NOCLUSTER) &&
+	   !(osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_LOCAL_MOUNT))
+		printk(KERN_NOTICE "ocfs2: The shared device (%s) is mounted "
+		       "without cluster aware mode.\n", osb->dev_str);
+
 	atomic_set(&osb->vol_state, VOLUME_MOUNTED);
 	wake_up(&osb->osb_mount_event);
 
@@ -1445,6 +1460,9 @@ static int ocfs2_parse_options(struct super_block *sb,
 		case Opt_journal_async_commit:
 			mopt->mount_opt |= OCFS2_MOUNT_JOURNAL_ASYNC_COMMIT;
 			break;
+		case Opt_nocluster:
+			mopt->mount_opt |= OCFS2_MOUNT_NOCLUSTER;
+			break;
 		default:
 			mlog(ML_ERROR,
 			     "Unrecognized mount option \"%s\" "
@@ -1556,6 +1574,9 @@ static int ocfs2_show_options(struct seq_file *s, struct dentry *root)
 	if (opts & OCFS2_MOUNT_JOURNAL_ASYNC_COMMIT)
 		seq_printf(s, ",journal_async_commit");
 
+	if (opts & OCFS2_MOUNT_NOCLUSTER)
+		seq_printf(s, ",nocluster");
+
 	return 0;
 }