loop: fix loop_validate_block_size() can't make sense

hulk inclusion
category: bugfix
bugzilla: 176146 https://gitee.com/openeuler/kernel/issues/I4DDEL



---------------------------

We config the block size of a loop device throuth
the following process:

lo_ioctl(..., unsigned long arg)
|                      ^^^^
lo_simple_ioctl(..., unsigned long arg)
|                             ^^^^
loop_set_block_size(..., unsigned long arg)
        |                         ^^^^
        loop_validate_block_size(unsigned short bsize)
        |                                 ^^^^^
        blk_queue_logical_block_size(..., unsigned int size) {
                '''
                limits->logical_block_size = size;
                        ^^^^ int
                '''
        }

loop_validate_block_size() will check the validity of bsize.
But long to short will be truncated(eg arg=1049600 and
it becomes 1024 after truncation by short. The block size
must within the range of 512 ~ PAGE_SZIE, This truncation will
turn illegal block szie to legal). The wrong of block size will
raise other errors.

Fixes: 3448914e ("loop: Add LOOP_CONFIGURE ioctl")
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>