• FUJITA Tomonori's avatar
    block: move the padding adjustment to blk_rq_map_sg · f18573ab
    FUJITA Tomonori authored
    blk_rq_map_user adjusts bi_size of the last bio. It breaks the rule
    that req->data_len (the true data length) is equal to sum(bio). It
    broke the scsi command completion code.
    
    commit e97a294e was introduced to fix
    the above issue. However, the partial completion code doesn't work
    with it. The commit is also a layer violation (scsi mid-layer should
    not know about the block layer's padding).
    
    This patch moves the padding adjustment to blk_rq_map_sg (suggested by
    James). The padding works like the drain buffer. This patch breaks the
    rule that req->data_len is equal to sum(sg), however, the drain buffer
    already broke it. So this patch just restores the rule that
    req->data_len is equal to sub(bio) without breaking anything new.
    
    Now when a low level driver needs padding, blk_rq_map_user and
    blk_rq_map_user_iov guarantee there's enough room for padding.
    blk_rq_map_sg can safely extend the last entry of a scatter list.
    
    blk_rq_map_sg must extend the last entry of a scatter list only for a
    request that got through bio_copy_user_iov. This patches introduces
    new REQ_COPY_USER flag.
    Signed-off-by: default avatarFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    Cc: Tejun Heo <htejun@gmail.com>
    Cc: Mike Christie <michaelc@cs.wisc.edu>
    Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
    Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
    f18573ab
blk-map.c 6.82 KB