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The build_user_data() function packs multiple fields into a __u64 value using bit shifts. Without explicit __u64 casts before shifting, the shift operations are performed on 32-bit unsigned integers before being promoted to 64-bit, causing data loss. Specifically, when tgt_data >= 256, the expression (tgt_data << 24) shifts on a 32-bit value, truncating the upper 8 bits before promotion to __u64. Since tgt_data can be up to 16 bits (assertion allows up to 65535), values >= 256 would have their high byte lost. Add explicit __u64 casts to both op and tgt_data before shifting to ensure the shift operations happen in 64-bit space, preserving all bits of the input values. user_data_to_tgt_data() is only used by stripe.c, in which the max supported member disks are 4, so won't trigger this issue. Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>