btrfs: add metadata_uuid to FS_INFO ioctl

Add retrieval of the filesystem's metadata UUID to the fsinfo ioctl.
This is driven by setting the BTRFS_FS_INFO_FLAG_METADATA_UUID flag in
btrfs_ioctl_fs_info_args::flags.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 55dd20d0f9cb75a20bfd31deff529ab85825b64e..b4ddf51ae3770fe5e29ec0f28f6a06dbeb2300bb 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3252,6 +3252,12 @@ static long btrfs_ioctl_fs_info(struct btrfs_fs_info *fs_info,
                fi_args->flags |= BTRFS_FS_INFO_FLAG_GENERATION;
        }
 
+       if (flags_in & BTRFS_FS_INFO_FLAG_METADATA_UUID) {
+               memcpy(&fi_args->metadata_uuid, fs_devices->metadata_uuid,
+                      sizeof(fi_args->metadata_uuid));
+               fi_args->flags |= BTRFS_FS_INFO_FLAG_METADATA_UUID;
+       }
+
        if (copy_to_user(arg, fi_args, sizeof(*fi_args)))
                ret = -EFAULT;
 

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 9b82e01c191d165a3f04dceaf1791193e97ad962..2c39d15a2beb454256ddd8f26733993858bf3c0d 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -252,6 +252,8 @@ struct btrfs_ioctl_dev_info_args {
 
 /* Request information about filesystem generation */
 #define BTRFS_FS_INFO_FLAG_GENERATION                  (1 << 1)
+/* Request information about filesystem metadata UUID */
+#define BTRFS_FS_INFO_FLAG_METADATA_UUID               (1 << 2)
 
 struct btrfs_ioctl_fs_info_args {
        __u64 max_id;                           /* out */
@@ -265,7 +267,8 @@ struct btrfs_ioctl_fs_info_args {
        __u16 csum_size;                        /* out */
        __u64 flags;                            /* in/out */
        __u64 generation;                       /* out */
-       __u8 reserved[960];                     /* pad to 1k */
+       __u8 metadata_uuid[BTRFS_FSID_SIZE];    /* out */
+       __u8 reserved[944];                     /* pad to 1k */
 };
 
 /*