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 | 118 +++++++++++++++++++++++++++++++++++++++++++++
include/uapi/linux/btrfs.h | 51 ++++++++++++++++++++
2 files changed, 169 insertions(+)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 111ee282b777..852421ac81cd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2309,6 +2309,122 @@ 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 __user *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) {
+ /* If the subvolume is a snapshot, offset is not zero */
+ u64 objectid = key.objectid;
+
+ 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;
+
+ 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 (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)
{
@@ -5663,6 +5779,8 @@ 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
--
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