From 2943868a909f1d526da363dc077fd7b578643f4b Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Sat, 11 Feb 2023 19:53:05 +0800 Subject: [PATCH] btrfs: ioctl: return device fsid from DEV_INFO ioctl Currently user space utilizes dev info ioctl to grab the info of a certain devid, this includes its device uuid. But the returned info is not enough to determine if a device is a seed. Commit a26d60dedf9a ("btrfs: sysfs: add devinfo/fsid to retrieve actual fsid from the device") exports the same value in sysfs so this is for parity with ioctl. 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 combinations: - 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 find the fsid member is no longer zero, and trust its value. Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/ioctl.c | 1 + include/uapi/linux/btrfs.h | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 8ea557e22252..439a5bf5ebc6 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -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 diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index b4f0f9531119..ada0a489bf2b 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -245,7 +245,17 @@ 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 seeding one. + * + * Introduced in v6.3, 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[377]; /* pad to 4k */ __u8 path[BTRFS_DEVICE_PATH_NAME_MAX]; /* out */ };