diff mbox

[RFC,v8,2/2] Btrfs: Add a new ioctl to set/change the label of a mounted file system

Message ID 50DD1530.5020308@oracle.com (mailing list archive)
State New, archived
Headers show

Commit Message

jeff.liu Dec. 28, 2012, 3:42 a.m. UTC 
With this new ioctl(2) BTRFS_IOC_SET_FSLABEL, we can set/change the label of a mounted file system.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: David Sterba <dsterba@suse.cz>

---
 fs/btrfs/ioctl.c |   39 +++++++++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 41 insertions(+)

Comments

David Sterba Dec. 28, 2012, 12:03 p.m. UTC | #1 
On Fri, Dec 28, 2012 at 11:42:40AM +0800, Jeff Liu wrote:
> +static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
> +{
> +	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
> +	struct btrfs_super_block *super_block = root->fs_info->super_copy;
> +	struct btrfs_trans_handle *trans;
> +	char label[BTRFS_LABEL_SIZE];
> +	int ret;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
> +	if (copy_from_user(label, arg, sizeof(label)))
> +		return -EFAULT;
> +
> +	if (strnlen(label, BTRFS_LABEL_SIZE) == BTRFS_LABEL_SIZE)

I would expect a message if this happens, similar to the 'get_fslabel'
one, otherwise it's difficult to find out the reason.

> +		return -EINVAL;
> +
> +	ret = mnt_want_write_file(file);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&root->fs_info->volume_mutex);
> +	trans = btrfs_start_transaction(root, 1);

Do we need to reserve 1 unit here? This does not touch any
non-superblock metadata, modifies superblock in place. This could lead
to an ENOSPC (changing label on a full fs), altghouh it need not happen.

> +	if (IS_ERR(trans)) {
> +		ret = PTR_ERR(trans);
> +		goto out_unlock;
> +	}
> +
> +	strcpy(super_block->label, label);
> +	ret = btrfs_end_transaction(trans, root);
> +
> +out_unlock:
> +	mutex_unlock(&root->fs_info->volume_mutex);
> +	mnt_drop_write_file(file);
> +	return ret;
> +}
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
jeff.liu Dec. 31, 2012, 10:23 a.m. UTC | #2 
On 12/28/2012 08:03 PM, David Sterba wrote:
> On Fri, Dec 28, 2012 at 11:42:40AM +0800, Jeff Liu wrote:
>> +static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
>> +{
>> +	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
>> +	struct btrfs_super_block *super_block = root->fs_info->super_copy;
>> +	struct btrfs_trans_handle *trans;
>> +	char label[BTRFS_LABEL_SIZE];
>> +	int ret;
>> +
>> +	if (!capable(CAP_SYS_ADMIN))
>> +		return -EPERM;
>> +
>> +	if (copy_from_user(label, arg, sizeof(label)))
>> +		return -EFAULT;
>> +
>> +	if (strnlen(label, BTRFS_LABEL_SIZE) == BTRFS_LABEL_SIZE)
> 
> I would expect a message if this happens, similar to the 'get_fslabel'
> one, otherwise it's difficult to find out the reason.
That's sounds make sense.
> 
>> +		return -EINVAL;
>> +
>> +	ret = mnt_want_write_file(file);
>> +	if (ret)
>> +		return ret;
>> +
>> +	mutex_lock(&root->fs_info->volume_mutex);
>> +	trans = btrfs_start_transaction(root, 1);
> 
> Do we need to reserve 1 unit here? This does not touch any
> non-superblock metadata, modifies superblock in place. This could lead
> to an ENOSPC (changing label on a full fs), altghouh it need not happen.
Don't need, I can not recalled why I did that before, will fix it.

Thanks,
-Jeff
> 
>> +	if (IS_ERR(trans)) {
>> +		ret = PTR_ERR(trans);
>> +		goto out_unlock;
>> +	}
>> +
>> +	strcpy(super_block->label, label);
>> +	ret = btrfs_end_transaction(trans, root);
>> +
>> +out_unlock:
>> +	mutex_unlock(&root->fs_info->volume_mutex);
>> +	mnt_drop_write_file(file);
>> +	return ret;
>> +}

--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 4be5d15..7383f49 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3719,6 +3719,43 @@  static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
 	return ret ? -EFAULT : 0;
 }
 
+static int btrfs_ioctl_set_fslabel(struct file *file, void __user *arg)
+{
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+	struct btrfs_super_block *super_block = root->fs_info->super_copy;
+	struct btrfs_trans_handle *trans;
+	char label[BTRFS_LABEL_SIZE];
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (copy_from_user(label, arg, sizeof(label)))
+		return -EFAULT;
+
+	if (strnlen(label, BTRFS_LABEL_SIZE) == BTRFS_LABEL_SIZE)
+		return -EINVAL;
+
+	ret = mnt_want_write_file(file);
+	if (ret)
+		return ret;
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out_unlock;
+	}
+
+	strcpy(super_block->label, label);
+	ret = btrfs_end_transaction(trans, root);
+
+out_unlock:
+	mutex_unlock(&root->fs_info->volume_mutex);
+	mnt_drop_write_file(file);
+	return ret;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3819,6 +3856,8 @@  long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_limit(root, argp);
 	case BTRFS_IOC_GET_FSLABEL:
 		return btrfs_ioctl_get_fslabel(file, argp);
+	case BTRFS_IOC_SET_FSLABEL:
+		return btrfs_ioctl_set_fslabel(file, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 5b2cbef..2abe239 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -453,6 +453,8 @@  struct btrfs_ioctl_send_args {
 			       struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
 				   char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 50, \
+				   char[BTRFS_LABEL_SIZE])
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
 #endif