[PATCH] Btrfs: add label to snapshot and subvol

[Anand jain <Anand.Jain@oracle.com>]

From: Anand Jain <anand.jain@oracle.com>

This modifies the struct btrfs_root_item to hold the label,
and make it v3 of this structure.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/ctree.h       |   14 ++++++++++++++
 fs/btrfs/ioctl.c       |   32 ++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h       |    2 ++
 fs/btrfs/root-tree.c   |   44 +++++++++++++++++++++++---------------------
 fs/btrfs/transaction.c |    1 +
 5 files changed, 72 insertions(+), 21 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 994d255..b280256 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -759,6 +759,10 @@ struct btrfs_root_item {
 	struct btrfs_timespec otime;
 	struct btrfs_timespec stime;
 	struct btrfs_timespec rtime;
+
+	__le64 generation_v3;
+	char label[BTRFS_LABEL_SIZE]; /* Add label to subvol */
+	
 	__le64 reserved[8]; /* for future */
 } __attribute__ ((__packed__));
 
@@ -2428,6 +2432,8 @@ BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct btrfs_root_item,
 			 last_snapshot, 64);
 BTRFS_SETGET_STACK_FUNCS(root_generation_v2, struct btrfs_root_item,
 			 generation_v2, 64);
+BTRFS_SETGET_STACK_FUNCS(root_generation_v3, struct btrfs_root_item,
+			 generation_v3, 64);
 BTRFS_SETGET_STACK_FUNCS(root_ctransid, struct btrfs_root_item,
 			 ctransid, 64);
 BTRFS_SETGET_STACK_FUNCS(root_otransid, struct btrfs_root_item,
@@ -2441,6 +2447,14 @@ static inline bool btrfs_root_readonly(struct btrfs_root *root)
 {
 	return (root->root_item.flags & cpu_to_le64(BTRFS_ROOT_SUBVOL_RDONLY)) != 0;
 }
+static inline char * btrfs_root_label(struct btrfs_root *root)
+{
+	return (root->root_item.label);
+}
+static inline void btrfs_root_set_label(struct btrfs_root *root, char *val)
+{
+	memcpy(root->root_item.label,val,BTRFS_LABEL_SIZE);
+}
 
 /* struct btrfs_root_backup */
 BTRFS_SETGET_STACK_FUNCS(backup_tree_root, struct btrfs_root_backup,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e58bd9d..cce0128 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3725,6 +3725,34 @@ static int btrfs_ioctl_set_label(struct btrfs_root *root, void __user *arg)
 	return 0;
 }
 
+static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
+						void __user *arg)
+{
+	char *label;
+
+	label = btrfs_root_label(root);
+	if (copy_to_user(arg, label, BTRFS_LABEL_SIZE))
+		return -EFAULT;
+	return 0;
+}
+
+static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root,
+						void __user *arg)
+{
+	char label[BTRFS_LABEL_SIZE];
+	struct btrfs_trans_handle *trans;
+
+	if (copy_from_user(label, arg, BTRFS_LABEL_SIZE))
+		return -EFAULT;
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+	btrfs_root_set_label(root, label);
+	btrfs_commit_transaction(trans, root);
+
+	return 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3827,6 +3855,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_get_label(root, argp);
 	case BTRFS_IOC_SET_LABEL:
 		return btrfs_ioctl_set_label(root, argp);
+	case BTRFS_IOC_SUBVOL_GETLABEL:
+		return btrfs_ioctl_subvol_getlabel(root, argp);
+	case BTRFS_IOC_SUBVOL_SETLABEL:
+		return btrfs_ioctl_subvol_setlabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 0c60fcb..1009a0c 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_GET_LABEL _IOR(BTRFS_IOCTL_MAGIC, 53, __u64)
 #define BTRFS_IOC_SET_LABEL _IOW(BTRFS_IOCTL_MAGIC, 54, __u64)
+#define BTRFS_IOC_SUBVOL_GETLABEL _IOWR(BTRFS_IOCTL_MAGIC, 55, __u64)
+#define BTRFS_IOC_SUBVOL_SETLABEL _IOW(BTRFS_IOCTL_MAGIC, 56, __u64)
 #endif
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index eb923d0..2a9ae5f 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -35,32 +35,34 @@ void btrfs_read_root_item(struct btrfs_root *root,
 {
 	uuid_le uuid;
 	int len;
-	int need_reset = 0;
 
 	len = btrfs_item_size_nr(eb, slot);
 	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
 			min_t(int, len, (int)sizeof(*item)));
-	if (len < sizeof(*item))
-		need_reset = 1;
-	if (!need_reset && btrfs_root_generation(item)
-		!= btrfs_root_generation_v2(item)) {
-		if (btrfs_root_generation_v2(item) != 0) {
-			printk(KERN_WARNING "btrfs: mismatching "
-					"generation and generation_v2 "
-					"found in root item. This root "
-					"was probably mounted with an "
-					"older kernel. Resetting all "
-					"new fields.\n");
-		}
-		need_reset = 1;
-	}
-	if (need_reset) {
-		memset(&item->generation_v2, 0,
-			sizeof(*item) - offsetof(struct btrfs_root_item,
-					generation_v2));
 
-		uuid_le_gen(&uuid);
-		memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
+	/* when len is gt sizeof(*item) that means its downgrade and
+	   the new members won't be touched anyways
+	   if len is lt sizeof(*item) its upgrade, we need to take
+	   care to set/reset newer members.
+	*/
+	if (len < sizeof(*item)) {
+		/* there is an upgrade need to set/reset the new members 
+		   assume v1 v2 v3 it can be upgrade from
+			v1 to v2 (set/reset only new members of v2)
+			v2 to v3 (set/reset only new members of v3)
+			v1 to v3 (set/reset new to v1)
+		*/
+		if (btrfs_root_generation(item) != btrfs_root_generation_v2(item)) {
+			//memset(&item->generation_v2, 0, 
+				//sizeof(*item) - offsetof(struct btrfs_root_item, generation_v2));
+			memset(&item->generation_v2, 0, sizeof(*item) - len);
+			uuid_le_gen(&uuid);
+			memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
+		} else if (btrfs_root_generation_v2(item) != btrfs_root_generation_v3(item)) {
+			//memset(&item->generation_v3, 0,
+			//	sizeof(*item) - offsetof(struct btrfs_root_item, generation_v3));
+			memset(&item->generation_v3, 0, sizeof(*item) - len);
+		}
 	}
 }
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 04bbfb1..45bff43 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1116,6 +1116,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	btrfs_set_root_otransid(new_root_item, trans->transid);
 	memset(&new_root_item->stime, 0, sizeof(new_root_item->stime));
 	memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
+	memset(new_root_item->label, 0, BTRFS_LABEL_SIZE);
 	btrfs_set_root_stransid(new_root_item, 0);
 	btrfs_set_root_rtransid(new_root_item, 0);
 
-- 
1.7.1