On 2018/05/18 10:10, Qu Wenruo wrote:
>
>
> On 2018年05月18日 09:00, Misono Tomohiro wrote:
>> On 2018/05/17 15:39, Qu Wenruo wrote:
>>>
>>>
>>> On 2018年05月16日 13:49, Tomohiro Misono wrote:
>>>> 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);
>>>
>>> What about just using btrfs_get_fs_root()?
>>>
>>> It would save several lines, and have better error handling along with
>>> better tree cache.
>>
>> Here we search ROOT_ITEM of subvolume in root_tree and
>> I don't think btrfs_get_fs_root() would save lines, right?
>
> btrfs_root has root_item member.
>
> So just btrfs_get_fs_root(), then use root->root_item.
Ok, I see. Thanks for you kind help.
>
>
>>>> + 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;
>>>> + }
>>>> + }
>
> These lines can be saved.
>
> Thanks,
> Qu
>
>>>> + 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 */
>>>>
>>>
>>
>
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