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