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.
>>> + 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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