btrfs: fix type of parameter generation in btrfs_get_dentry

The type of parameter generation has been u32 since the beginning,
however all callers pass a u64 generation, so unify the types to prevent
potential loss.

CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/export.c

@@ -58,7 +58,7 @@ static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
 }
 
 struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
-				u64 root_objectid, u32 generation,
+				u64 root_objectid, u64 generation,
 				int check_generation)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);

fs/btrfs/export.h

@@ -19,7 +19,7 @@ struct btrfs_fid {
 } __attribute__ ((packed));
 
 struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
-				u64 root_objectid, u32 generation,
+				u64 root_objectid, u64 generation,
 				int check_generation);
 struct dentry *btrfs_get_parent(struct dentry *child);