@@ -2859,6 +2859,7 @@ static long btrfs_ioctl_dev_info(struct btrfs_fs_info *fs_info,
di_args->bytes_used = btrfs_device_get_bytes_used(dev);
di_args->total_bytes = btrfs_device_get_total_bytes(dev);
memcpy(di_args->uuid, dev->uuid, sizeof(di_args->uuid));
+ memcpy(di_args->fsid, dev->fs_devices->fsid, BTRFS_UUID_SIZE);
if (dev->name)
strscpy(di_args->path, btrfs_dev_name(dev), sizeof(di_args->path));
else
@@ -245,7 +245,18 @@ struct btrfs_ioctl_dev_info_args {
__u8 uuid[BTRFS_UUID_SIZE]; /* in/out */
__u64 bytes_used; /* out */
__u64 total_bytes; /* out */
- __u64 unused[379]; /* pad to 4k */
+ /*
+ * Optional, out.
+ *
+ * Showing the fsid of the device, allowing user space
+ * to check if this device is a seed one.
+ *
+ * Introduced in v6.4, thus user space still needs to
+ * check if kernel changed this value.
+ * Older kernel will not touch the values here.
+ */
+ __u8 fsid[BTRFS_UUID_SIZE];
+ __u64 unused[363]; /* pad to 4k */
__u8 path[BTRFS_DEVICE_PATH_NAME_MAX]; /* out */
};
Currently user space utilize dev info ioctl to grab the info of a certain devid, this includes its device uuid. But the return info is not enough to determine if a device is a seed. This patch will add a new member, fsid, into btrfs_ioctl_dev_info_args, and populate the member with fsid value. This should not cause any compatibility problem, following the following combination: - Old user space, old kernel - Old user space, new kernel User space tool won't even check the new member. - New user space, old kernel The kernel won't touch the new member, and user space tool should zero out its argument, thus the new member is all zero. User space tool can then know the kernel doesn't support this fsid reporting, and falls back to whatever they can. - New user space, new kernel Go as planned. Would found the fsid member is no longer zero, and trust its value. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/ioctl.c | 1 + include/uapi/linux/btrfs.h | 13 ++++++++++++- 2 files changed, 13 insertions(+), 1 deletion(-)