Add new unprivileged ioctl BTRFS_IOC_GET_SUBVOL_INFO which returns the information of subvolume containing this inode. (i.e. returns the information in ROOT_ITEM and ROOT_BACKREF.)
Signed-off-by: Tomohiro Misono <misono.tomoh...@jp.fujitsu.com> --- v4 -> v5 - Update error handling of btrfs_next_leaf() to cover all cases - Return error if ROOT_BACKREF is not found (except top-level) fs/btrfs/ioctl.c | 146 +++++++++++++++++++++++++++++++++++++++++++++ include/uapi/linux/btrfs.h | 51 ++++++++++++++++ 2 files changed, 197 insertions(+) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 48e2ddff32bd..c1c9ae9a937d 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2242,6 +2242,150 @@ static noinline int btrfs_ioctl_ino_lookup(struct file *file, return ret; } +/* Get the subvolume information in BTRFS_ROOT_ITEM and BTRFS_ROOT_BACKREF */ +static noinline int btrfs_ioctl_get_subvol_info(struct file *file, + void __user *argp) +{ + struct btrfs_ioctl_get_subvol_info_args *subvol_info; + struct btrfs_root *root; + struct btrfs_path *path; + struct btrfs_key key; + + struct btrfs_root_item root_item; + struct btrfs_root_ref *rref; + struct extent_buffer *l; + int slot; + + unsigned long item_off; + unsigned long item_len; + + struct inode *inode; + int ret; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + subvol_info = kzalloc(sizeof(*subvol_info), GFP_KERNEL); + if (!subvol_info) { + btrfs_free_path(path); + return -ENOMEM; + } + + inode = file_inode(file); + root = BTRFS_I(inode)->root->fs_info->tree_root; + + key.objectid = BTRFS_I(inode)->root->root_key.objectid; + key.type = BTRFS_ROOT_ITEM_KEY; + key.offset = 0; + + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) { + goto out; + } else if (ret > 0) { + u64 objectid = key.objectid; + + if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) { + ret = btrfs_next_leaf(root, path); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = -ENOENT; + goto out; + } + } + + /* If the subvolume is a snapshot, offset is not zero */ + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if (key.objectid != objectid || + key.type != BTRFS_ROOT_ITEM_KEY) { + ret = -ENOENT; + goto out; + } + } + + l = path->nodes[0]; + slot = path->slots[0]; + item_off = btrfs_item_ptr_offset(l, slot); + item_len = btrfs_item_size_nr(l, slot); + read_extent_buffer(l, &root_item, item_off, item_len); + + subvol_info->id = key.objectid; + + subvol_info->generation = btrfs_root_generation(&root_item); + subvol_info->flags = btrfs_root_flags(&root_item); + + memcpy(subvol_info->uuid, root_item.uuid, BTRFS_UUID_SIZE); + memcpy(subvol_info->parent_uuid, root_item.parent_uuid, + BTRFS_UUID_SIZE); + memcpy(subvol_info->received_uuid, root_item.received_uuid, + BTRFS_UUID_SIZE); + + subvol_info->ctransid = btrfs_root_ctransid(&root_item); + subvol_info->ctime.sec = btrfs_stack_timespec_sec(&root_item.ctime); + subvol_info->ctime.nsec = btrfs_stack_timespec_nsec(&root_item.ctime); + + subvol_info->otransid = btrfs_root_otransid(&root_item); + subvol_info->otime.sec = btrfs_stack_timespec_sec(&root_item.otime); + subvol_info->otime.nsec = btrfs_stack_timespec_nsec(&root_item.otime); + + subvol_info->stransid = btrfs_root_stransid(&root_item); + subvol_info->stime.sec = btrfs_stack_timespec_sec(&root_item.stime); + subvol_info->stime.nsec = btrfs_stack_timespec_nsec(&root_item.stime); + + subvol_info->rtransid = btrfs_root_rtransid(&root_item); + subvol_info->rtime.sec = btrfs_stack_timespec_sec(&root_item.rtime); + subvol_info->rtime.nsec = btrfs_stack_timespec_nsec(&root_item.rtime); + + btrfs_release_path(path); + if (key.objectid != BTRFS_FS_TREE_OBJECTID) { + key.type = BTRFS_ROOT_BACKREF_KEY; + key.offset = 0; + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) { + goto out; + } else if (path->slots[0] >= + btrfs_header_nritems(path->nodes[0])) { + ret = btrfs_next_leaf(root, path); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = -ENOENT; + goto out; + } + } + + l = path->nodes[0]; + slot = path->slots[0]; + btrfs_item_key_to_cpu(l, &key, slot); + if (key.objectid == subvol_info->id && + key.type == BTRFS_ROOT_BACKREF_KEY) { + subvol_info->parent_id = key.offset; + + rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref); + subvol_info->dirid = btrfs_root_ref_dirid(l, rref); + + item_off = btrfs_item_ptr_offset(l, slot) + + sizeof(struct btrfs_root_ref); + item_len = btrfs_item_size_nr(l, slot) + - sizeof(struct btrfs_root_ref); + read_extent_buffer(l, subvol_info->name, + item_off, item_len); + } else { + ret = -ENOENT; + goto out; + } + } + + if (copy_to_user(argp, subvol_info, sizeof(*subvol_info))) + ret = -EFAULT; + +out: + kzfree(subvol_info); + btrfs_free_path(path); + return ret; +} + static noinline int btrfs_ioctl_snap_destroy(struct file *file, void __user *arg) { @@ -5374,6 +5518,8 @@ long btrfs_ioctl(struct file *file, unsigned int return btrfs_ioctl_get_features(file, argp); case BTRFS_IOC_SET_FEATURES: return btrfs_ioctl_set_features(file, argp); + case BTRFS_IOC_GET_SUBVOL_INFO: + return btrfs_ioctl_get_subvol_info(file, argp); } return -ENOTTY; diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index c8d99b9ca550..02cd1f1994e8 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -725,6 +725,55 @@ struct btrfs_ioctl_send_args { __u64 reserved[4]; /* in */ }; +struct btrfs_ioctl_get_subvol_info_args { + /* All field is out */ + /* Id of this subvolume */ + __u64 id; + /* Name of this subvolume, used to get the real name at mount point */ + char name[BTRFS_VOL_NAME_MAX + 1]; + /* + * Id of the subvolume which contains this subvolume. + * Zero for top-level subvolume or deleted subvolume + */ + __u64 parent_id; + /* + * Inode number of the directory which contains this subvolume. + * Zero for top-level subvolume or deleted subvolume + */ + __u64 dirid; + + /* Latest transaction id of this subvolume */ + __u64 generation; + /* Flags of this subvolume */ + __u64 flags; + + /* uuid of this subvolume */ + __u8 uuid[BTRFS_UUID_SIZE]; + /* + * uuid of the subvolume of which this subvolume is a snapshot. + * All zero for non-snapshot subvolume + */ + __u8 parent_uuid[BTRFS_UUID_SIZE]; + /* + * uuid of the subvolume from which this subvolume is received. + * All zero for non-received subvolume + */ + __u8 received_uuid[BTRFS_UUID_SIZE]; + + /* Transaction id indicates when change/create/send/receive happens */ + __u64 ctransid; + __u64 otransid; + __u64 stransid; + __u64 rtransid; + /* Time corresponds to c/o/s/rtransid */ + struct btrfs_ioctl_timespec ctime; + struct btrfs_ioctl_timespec otime; + struct btrfs_ioctl_timespec stime; + struct btrfs_ioctl_timespec rtime; + + __u64 reserved[8]; +}; + /* Error codes as returned by the kernel */ enum btrfs_err_code { BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET = 1, @@ -843,5 +892,7 @@ enum btrfs_err_code { struct btrfs_ioctl_vol_args_v2) #define BTRFS_IOC_LOGICAL_INO_V2 _IOWR(BTRFS_IOCTL_MAGIC, 59, \ struct btrfs_ioctl_logical_ino_args) +#define BTRFS_IOC_GET_SUBVOL_INFO _IOR(BTRFS_IOCTL_MAGIC, 60, \ + struct btrfs_ioctl_get_subvol_info_args) #endif /* _UAPI_LINUX_BTRFS_H */ -- 2.14.3 -- 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