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.
> + }
> +
> + /* 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);
> + 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)
> + return ret;
Should goto out; to free subvol_info and path.
> + }
> +
> + 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 (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>
>
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