scsi: sd: block: Fix regressions in read-only block device handling

hulk inclusion
category: bugfix
bugzilla: 46833 https://gitee.com/openeuler/kernel/issues/I4DCSN

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

Fix:
https://gitee.com/src-openeuler/util-linux/issues/I28N07

Origin patch:
https://patchwork.kernel.org/project/linux-scsi/patch/20190227041941

.
1568-1-martin.petersen@oracle.com/

If partition table changed online, will record partition read-only flag.

Some devices come online in write protected state and switch to
read-write once they are ready to process I/O requests. These devices
broke with commit 20bd1d02 ("scsi: sd: Keep disk read-only when
re-reading partition") because we had no way to distinguish between a
user decision to set a block_device read-only and the actual hardware
device being write-protected.

Because partitions are dropped and recreated on revalidate we are
unable to persist any user-provided policy in hd_struct. Introduce a
bitmap in struct gendisk to track the user configuration. This bitmap
is updated when BLKROSET is called on a given disk or partition.

A helper function, get_user_ro(), is provided to determine whether the
ioctl has forced read-only state for a given block device. This helper
is used by set_disk_ro() and add_partition() to ensure that both
existing and newly created partitions will get the correct state.

 - If BLKROSET sets a whole disk device read-only, all partitions will
   now end up in a read-only state.

 - If BLKROSET sets a given partition read-only, that partition will
   remain read-only post revalidate.

 - Otherwise both the whole disk device and any partitions will
   reflect the write protect state of the underlying device.

Since nobody knows what "policy" means, rename the field to
"read_only" for clarity.

Cc: Jeremy Cline <jeremy@jcline.org>
Cc: Oleksii Kurochko <olkuroch@cisco.com>
Cc: stable@vger.kernel.org # v4.16+
Reported-by: Oleksii Kurochko <olkuroch@cisco.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201221


Fixes: 20bd1d02 ("scsi: sd: Keep disk read-only when re-reading partition")
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Ye Bin <yebin10@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>