Generally snapshots are machine generated, so at any point in time
if a sysadmin looks at a list of snapshots there should be some
info about the snapshots to indicate purpose of it being created.
With this patch and along with the corresponding btrfs-progs patch
a 32byte info can be added to the snapshots/subvol.
Further, ioctl is preferred over the attribute to write the label
since btrfs-progs is not only the application which might be
interacting with the subvol to write the label, for example
btrfs-gui might as well write the label, so that needs an
additional efforts to maintain a consistent keyword across the
applications is difficult in the long run.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/ctree.h | 12 +++++++++-
fs/btrfs/ioctl.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/transaction.c | 1 +
include/uapi/linux/btrfs.h | 2 ++
4 files changed, 72 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1679051..6b527bc 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -392,6 +392,7 @@ 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,
@@ -769,7 +770,8 @@ 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__));
/*
@@ -2546,6 +2548,14 @@ 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 2bbbed5..211b319 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3982,6 +3982,60 @@ out_unlock:
return ret;
}
+static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
+ void __user *arg)
+{
+ char *label;
+
+ spin_lock(&root->root_item_lock);
+ label = btrfs_root_label(&root->root_item);
+ if (copy_to_user(arg, label, BTRFS_SUBVOL_LABEL_SIZE)) {
+ spin_unlock(&root->root_item_lock);
+ return -EFAULT;
+ }
+ spin_unlock(&root->root_item_lock);
+ return 0;
+}
+
+static int btrfs_ioctl_subvol_setlabel(struct file *file,
+ void __user *arg)
+{
+ char label[BTRFS_SUBVOL_LABEL_SIZE+1];
+ struct btrfs_trans_handle *trans;
+ struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+ struct inode *inode = file->f_path.dentry->d_inode;
+ int ret;
+
+ if (btrfs_root_readonly(root))
+ return -EROFS;
+
+ if (!inode_owner_or_capable(inode))
+ return -EACCES;
+
+ ret = mnt_want_write_file(file);
+ if (ret)
+ return ret;
+
+ if (copy_from_user(label, arg, BTRFS_SUBVOL_LABEL_SIZE)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ trans = btrfs_join_transaction(root);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ goto out;
+ }
+ spin_lock(&root->root_item_lock);
+ btrfs_root_set_label(&root->root_item, label);
+ spin_unlock(&root->root_item_lock);
+ btrfs_end_transaction(trans, root);
+
+out:
+ mnt_drop_write_file(file);
+ return ret;
+}
+
long btrfs_ioctl(struct file *file, unsigned int
cmd, unsigned long arg)
{
@@ -4086,6 +4140,10 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_get_fslabel(file, argp);
case BTRFS_IOC_SET_FSLABEL:
return btrfs_ioctl_set_fslabel(file, argp);
+ case BTRFS_IOC_SUBVOL_GETLABEL:
+ return btrfs_ioctl_subvol_getlabel(root, argp);
+ case BTRFS_IOC_SUBVOL_SETLABEL:
+ return btrfs_ioctl_subvol_setlabel(file, argp);
}
return -ENOTTY;
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 955204c..955097e 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1181,6 +1181,7 @@ 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);
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index fa3a5f9..38d0f56 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -510,5 +510,7 @@ struct btrfs_ioctl_send_args {
struct btrfs_ioctl_get_dev_stats)
#define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
struct btrfs_ioctl_dev_replace_args)
+#define BTRFS_IOC_SUBVOL_GETLABEL _IOWR(BTRFS_IOCTL_MAGIC, 55, __u64)
+#define BTRFS_IOC_SUBVOL_SETLABEL _IOW(BTRFS_IOCTL_MAGIC, 56, __u64)
#endif /* _UAPI_LINUX_BTRFS_H */
--
1.8.1.227.g44fe835
--
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