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Btrfs: get/set label of a mounted file system

RFC PATCH Superseded Jeff Liu 2 participants 6 messages Dec 28, 2012 – Dec 31, 2012 Btrfs file system

v8 of 9 Superseded Latest is v9 →

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Jeff Liu

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#0 lore raw

v8 cover Btrfs: get/set label of a mounted file system

Hello,

Here is the updated version of introduce get/set_or_change label upon a mounted filesystem.

v8->v7:
btrfs_ioc_fs_getlabel():
- Examine the label length with strnlen().
- Tweak up warn() info if the label is not NUL terminated according to Goffredo's suggestions.

The old versions can be found at:
v7:
http://www.spinics.net/lists/linux-btrfs/msg20994.html

v6:
http://www.spinics.net/lists/linux-btrfs/msg20922.html

v5:
http://www.spinics.net/lists/linux-btrfs/msg20888.html

v4:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/21618

v3:
https://patchwork.kernel.org/patch/1124642/

v2:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/12877

v1:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/12872

Thanks,
-Jeff

author
#1 lore raw

RFC PATCH v8 1/2 Btrfs: Add a new ioctl to get the label of a mounted file system

Add a new ioctl(2) BTRFS_IOC_GET_FSLABLE, so that we can get the label upon a mounted file system.

Signed-off-by Jie Liu <[email protected]>
Signed-off-by Anand Jain <[email protected]>
Cc Miao Xie <[email protected]>
Cc Goffredo Baroncelli <[email protected]>
Cc David Sterba <[email protected]>
---
 fs/btrfs/ioctl.c |   22 ++++++++++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 24 insertions(+)
fs/btrfs/ioctl.c +22 -0
index 8fcf9a5..4be5d15 100644
@@ -3699,6 +3699,26 @@ out:
 	return ret;
 }
 
+static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
+{
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+	const char *label = root->fs_info->super_copy->label;
+	size_t len = strnlen(label, BTRFS_LABEL_SIZE);
+	int ret;
+
+	if (len == BTRFS_LABEL_SIZE) {
+		len--;
+		WARN(1, "btrfs: device label is not zero terminated, "
+			"it will be truncated to %zu bytes.\n", len);
+	}
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = copy_to_user(arg, label, len);
+	mutex_unlock(&root->fs_info->volume_mutex);
+
+	return ret ? -EFAULT : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {

@@ -3797,6 +3817,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_create(root, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
 		return btrfs_ioctl_qgroup_limit(root, argp);
+	case BTRFS_IOC_GET_FSLABEL:
+		return btrfs_ioctl_get_fslabel(file, argp);
 	}
 
 	return -ENOTTY;
fs/btrfs/ioctl.h +2 -0
index 731e287..5b2cbef 100644
@@ -451,6 +451,8 @@ struct btrfs_ioctl_send_args {
 			       struct btrfs_ioctl_qgroup_create_args)
 #define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
 			       struct btrfs_ioctl_qgroup_limit_args)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
+				   char[BTRFS_LABEL_SIZE])
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
 #endif
Signature · 1 line
1.7.9.5
#2 lore raw

Re: [RFC PATCH v8 1/2] Btrfs: Add a new ioctl to get the label of a mounted file system

fs/btrfs/ioctl.c out: · line 3712

Quoted 11 lines · Jeff Liu
fs/btrfs/ioctl.c +11 -0
+static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg)
+{
+	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+	const char *label = root->fs_info->super_copy->label;
+	size_t len = strnlen(label, BTRFS_LABEL_SIZE);
+	int ret;
+
+	if (len == BTRFS_LABEL_SIZE) {
+		len--;
+		WARN(1, "btrfs: device label is not zero terminated, "
+			"it will be truncated to %zu bytes.\n", len);

This will print a stacktrace, it's not needed in this context, the warning is enough.

		printk(KERN_WARNING "...");
Quoted 8 lines
fs/btrfs/ioctl.c +8 -0
+	}
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = copy_to_user(arg, label, len);
+	mutex_unlock(&root->fs_info->volume_mutex);
+
+	return ret ? -EFAULT : 0;
+}
author
#3 lore raw

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

In reply to Jeff Liu

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 <[email protected]>
Signed-off-by Anand Jain <[email protected]>
Reviewed-by Miao Xie <[email protected]>
Reviewed-by Goffredo Baroncelli <[email protected]>
Reviewed-by David Sterba <[email protected]>
---
 fs/btrfs/ioctl.c |   39 +++++++++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 41 insertions(+)
fs/btrfs/ioctl.c +39 -0
index 4be5d15..7383f49 100644
@@ -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;
fs/btrfs/ioctl.h +2 -0
index 5b2cbef..2abe239 100644
@@ -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
Signature · 1 line
1.7.9.5
#4 lore raw

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

Quoted 5 lines · Jeff Liu
fs/btrfs/ioctl.c +5 -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;

fs/btrfs/ioctl.c static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg) · line 3736

Quoted 10 lines
fs/btrfs/ioctl.c +10 -0
+	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.

fs/btrfs/ioctl.c static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg) · line 3744

Quoted 8 lines
fs/btrfs/ioctl.c +8 -0
+		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.

Quoted 13 lines
fs/btrfs/ioctl.c +13 -0
+	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;
+}
author
#5 lore raw

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

Quoted 11 lines · David Sterba
Quoted 10 lines · Jeff Liu
fs/btrfs/ioctl.c +10 -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;
Quoted 8 lines

fs/btrfs/ioctl.c static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg) · line 3736

Quoted 5 lines
fs/btrfs/ioctl.c +5 -0
+
+	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.

Quoted 13 lines

fs/btrfs/ioctl.c static int btrfs_ioctl_get_fslabel(struct file *file, void __user *arg) · line 3744

Quoted 9 lines
fs/btrfs/ioctl.c +8 -0
+		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

Quoted 14 lines
Quoted 14 lines
fs/btrfs/ioctl.c +13 -0
+	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;
+}