[v2] Btrfs: add label to snapshot and subvol

Commit Message

Anand Jain Nov. 16, 2012, 4:52 a.m. UTC

From: Anand Jain <[e-mail]>

v1->v2:
This adds a new member label in the btrfs_root_item struct,
which uses 32 bytes of the reserved 64 bytes. So that 
btrfs_root_item remains same.

Signed-off-by: Anand Jain <[e-mail]>
---
 fs/btrfs/ctree.h       |   12 +++++++++++-
 fs/btrfs/ioctl.c       |   32 ++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h       |    2 ++
 fs/btrfs/transaction.c |    1 +
 4 files changed, 46 insertions(+), 1 deletions(-)

Comments

Miao Xie Nov. 16, 2012, 6:33 a.m. UTC | #1

Hi, Anand

On fri, 16 Nov 2012 12:52:25 +0800, Anand jain wrote:
> +static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
> +						void __user *arg)
> +{
> +	char *label;
> +
> +	label = btrfs_root_label(&root->root_item);
> +	if (copy_to_user(arg, label, BTRFS_SUBVOL_LABEL_SIZE))
> +		return -EFAULT;
> +	return 0;
> +}
> +
> +static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root,
> +						void __user *arg)
> +{
> +	char label[BTRFS_SUBVOL_LABEL_SIZE+1];
> +	struct btrfs_trans_handle *trans;
> +
> +	if (copy_from_user(label, arg, BTRFS_SUBVOL_LABEL_SIZE))
> +		return -EFAULT;
> +	trans = btrfs_join_transaction(root);
> +	if (IS_ERR(trans))
> +		return PTR_ERR(trans);
> +	btrfs_root_set_label(&root->root_item, label);
> +	btrfs_end_transaction(trans, root);

We need a lock to protect the label, and besides that, we need to get the write
access before we set the label for the subvolume.

Thanks
Miao

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Anand Jain Nov. 27, 2012, 6:26 p.m. UTC | #2

Hi Maio,

  Thanks for the review.
  Was away for sometime sorry for delay, have sent out the
  patch with review comments accepted.

-Anand

On 11/16/2012 02:33 PM, Miao Xie wrote:
> Hi, Anand
>
> On fri, 16 Nov 2012 12:52:25 +0800, Anand jain wrote:
>> +static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
>> +						void __user *arg)
>> +{
>> +	char *label;
>> +
>> +	label = btrfs_root_label(&root->root_item);
>> +	if (copy_to_user(arg, label, BTRFS_SUBVOL_LABEL_SIZE))
>> +		return -EFAULT;
>> +	return 0;
>> +}
>> +
>> +static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root,
>> +						void __user *arg)
>> +{
>> +	char label[BTRFS_SUBVOL_LABEL_SIZE+1];
>> +	struct btrfs_trans_handle *trans;
>> +
>> +	if (copy_from_user(label, arg, BTRFS_SUBVOL_LABEL_SIZE))
>> +		return -EFAULT;
>> +	trans = btrfs_join_transaction(root);
>> +	if (IS_ERR(trans))
>> +		return PTR_ERR(trans);
>> +	btrfs_root_set_label(&root->root_item, label);
>> +	btrfs_end_transaction(trans, root);
>
> We need a lock to protect the label, and besides that, we need to get the write
> access before we set the label for the subvolume.
>
> Thanks
> Miao
>
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>
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Patch

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 994d255..039e11c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -383,6 +383,7 @@  struct btrfs_header {
  */
 #define BTRFS_SYSTEM_CHUNK_ARRAY_SIZE 2048
 #define BTRFS_LABEL_SIZE 256
+#define BTRFS_SUBVOL_LABEL_SIZE 32
 
 /*
  * just in case we somehow lose the roots and are not able to mount,
@@ -759,7 +760,8 @@  struct btrfs_root_item {
 	struct btrfs_timespec otime;
 	struct btrfs_timespec stime;
 	struct btrfs_timespec rtime;
-	__le64 reserved[8]; /* for future */
+	char label[BTRFS_SUBVOL_LABEL_SIZE];
+	__le64 reserved[4]; /* for future */
 } __attribute__ ((__packed__));
 
 /*
@@ -2441,6 +2443,14 @@  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_item *root_item)
+{
+	return (root_item->label);
+}
+static inline void btrfs_root_set_label(struct btrfs_root_item *root_item, char *val)
+{
+	memcpy(root_item->label, val, BTRFS_SUBVOL_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..aa4eb23 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->root_item);
+	if (copy_to_user(arg, label, BTRFS_SUBVOL_LABEL_SIZE))
+		return -EFAULT;
+	return 0;
+}
+
+static int btrfs_ioctl_subvol_setlabel(struct btrfs_root *root,
+						void __user *arg)
+{
+	char label[BTRFS_SUBVOL_LABEL_SIZE+1];
+	struct btrfs_trans_handle *trans;
+
+	if (copy_from_user(label, arg, BTRFS_SUBVOL_LABEL_SIZE))
+		return -EFAULT;
+	trans = btrfs_join_transaction(root);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+	btrfs_root_set_label(&root->root_item, label);
+	btrfs_end_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/transaction.c b/fs/btrfs/transaction.c
index 04bbfb1..0a3f8b3 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1118,6 +1118,7 @@  static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
 	btrfs_set_root_stransid(new_root_item, 0);
 	btrfs_set_root_rtransid(new_root_item, 0);
+	memset(&new_root_item->label, 0, BTRFS_SUBVOL_LABEL_SIZE);
 
 	old = btrfs_lock_root_node(root);
 	ret = btrfs_cow_block(trans, root, old, NULL, 0, &old);