On 2018/05/15 16:57, Gu, Jinxiang/顾 金香 wrote:
> Hi, add a missed a comment.
>
>> -----Original Message-----
>> From: Misono Tomohiro [mailto:misono.tomoh...@jp.fujitsu.com]
>> Sent: Tuesday, May 15, 2018 3:04 PM
>> To: Gu, Jinxiang/顾 金香 <g...@cn.fujitsu.com>; linux-btrfs@vger.kernel.org
>> Subject: Re: [PATCH v4 1/3] btrfs: Add unprivileged ioctl which returns
>> subvolume information
>>
>> On 2018/05/15 15:31, Gu, Jinxiang/顾 金香 wrote:
>>> Hi,
>>>
>>>> -----Original Message-----
>>>> From: linux-btrfs-ow...@vger.kernel.org
>>>> [mailto:linux-btrfs-ow...@vger.kernel.org] On Behalf Of Tomohiro
>>>> Misono
>>>> Sent: Friday, May 11, 2018 3:26 PM
>>>> To: linux-btrfs@vger.kernel.org
>>>> Subject: [PATCH v4 1/3] btrfs: Add unprivileged ioctl which returns
>>>> subvolume information
>>>>
>>>> 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>
>>>> ---
>>>> fs/btrfs/ioctl.c | 129
>>>> +++++++++++++++++++++++++++++++++++++++++++++
>>>> include/uapi/linux/btrfs.h | 51 ++++++++++++++++++
>>>> 2 files changed, 180 insertions(+)
>>>>
>>>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index
>>>> 48e2ddff32bd..64b23e22852f 100644
>>>> --- a/fs/btrfs/ioctl.c
>>>> +++ b/fs/btrfs/ioctl.c
>>>> @@ -2242,6 +2242,133 @@ 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)
>>>> + return ret;
>>> Should goto out; to free subvol_info and path.
>> Thanks, will update both.
>>
>
> Since btrfs_next_leaf may return 1 when nritems of next leaf is 0,
> So, btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); may goes
> wrong.
> And I think it should add a judge before btrfs_item_key_to_cpu.
Ok, I will update to handle all cases.
[snip]>>>> + 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);
>>>> + }
>>> If this if is not correct(ex. corrupt filesystem without backref),
>>> should it return -ENOENT, or its be ok without parent_id, dirid and name.
>>> Suggest to add logic of else.
>>
>> If backref does not exist (except top-level subvolume), it means filesystem
>> corruption.
>> So, I'd like to return -EUCLEAN here.
On second thought, I notice if this ioctl is called after containing subvolume
is deleted,
the entry may not exist. So, -ENOENT is fine.
Thanks,
Tomohiro Misono
>>
>> Thanks,
>> Tomohiro Misono
>>
>>>
>>>> +
>>>> + 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 +5501,8 @@ 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..ed053852c71f 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 filed 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
>>>>
>>>
>>> Reviewed-by: Gu Jinxiang <g...@cn.fujitsu.com>
>>>>
>>>> --
>>>> 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
>>>>
>>>
--
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
