[Ocfs2-devel] [PATCH 3/4] re-enable "ocfs2: mount shared volume without ha stack"

[Heming Zhao via Ocfs2-devel <ocfs2-devel@oss.oracle.com>]

the key different between local mount and non-clustered mount:
local mount feature (tunefs.ocfs2 --fs-features=[no]local) can't do
convert job without ha stack. non-clustered mount feature can run
totally without ha stack.

commit 912f655d78c5 ("ocfs2: mount shared volume without ha stack") had
bug, then commit c80af0c250c8f8a3c978aa5aafbe9c39b336b813 reverted it.

Let's give some explain for the issue mentioned by commit c80af0c250c8.

Under Junxiao's call trace, in __ocfs2_find_empty_slot(), the 'if'
accessment is wrong. sl_node_num could be 0 at o2cb env.

with current information, the trigger flow (base on 912f655d78c5):
1>
nodeA with 'node_num = 0' for mounting. it will succeed.
at this time, slotmap extent block will contains es_valid:1 &
es_node_num:0 for nodeA
then ocfs2_update_disk_slot() will write back slotmap info to disk.

2>
then, nodeB with 'node_num = 1' for mounting
this time, osb->node_num is 1 (set by config file), osb->preferred is
OCFS2_INVALID_SLOT (set by ocfs2_parse_options).

ocfs2_find_slot
 + ocfs2_update_slot_info //read slotmap info from disk
 |  + set si->si_slots[0].es_valid = 1 & si->si_slots[0].sl_node_num = 0
 |
 + __ocfs2_node_num_to_slot //will return -ENOENT.
 + __ocfs2_find_empty_slot
    + if ((preferred >= 0) && (preferred < si->si_num_slots))
    |  fails enter this 'if' for preferred value is OCFS2_INVALID_SLOT
    |
    + 'for(i = 0; i < si->si_num_slots; i++)' search slot 0
      successfully.
    |  'si->si_slots[0].sl_node_num' is false. trigger 'break' condition.
    |
    + return slot 0.
       it will cause nodeB grab nodeA journal dlm lock, then trigger hung.

How to do for this bug?

This commit re-enabled 912f655d78c5, next commit (add MMP support) will fix
the issue.

Signed-off-by: Heming Zhao <heming.zhao@suse.com>
---
 fs/ocfs2/ocfs2.h    |  4 +++-
 fs/ocfs2/slot_map.c | 46 ++++++++++++++++++++++++++-------------------
 fs/ocfs2/super.c    | 21 +++++++++++++++++++++
 3 files changed, 51 insertions(+), 20 deletions(-)

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 740b64238312..337527571461 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -277,6 +277,7 @@ 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
@@ -672,7 +673,8 @@ 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)
diff --git a/fs/ocfs2/slot_map.c b/fs/ocfs2/slot_map.c
index da7718cef735..0b0ae3ebb0cf 100644
--- a/fs/ocfs2/slot_map.c
+++ b/fs/ocfs2/slot_map.c
@@ -252,14 +252,16 @@ 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;
 		}
@@ -454,24 +456,30 @@ 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;
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 438be028935d..f7298816d8d9 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -172,6 +172,7 @@ enum {
 	Opt_dir_resv_level,
 	Opt_journal_async_commit,
 	Opt_err_cont,
+	Opt_nocluster,
 	Opt_err,
 };
 
@@ -205,6 +206,7 @@ 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}
 };
 
@@ -616,6 +618,13 @@ 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)) {
@@ -856,6 +865,7 @@ 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,
@@ -1127,6 +1137,11 @@ 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);
 
@@ -1437,6 +1452,9 @@ 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\" "
@@ -1548,6 +1566,9 @@ 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;
 }
 
-- 
2.37.1


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