md/raid1,raid10: don't ignore IO flags

commit e879a0d9 upstream.

If blk-wbt is enabled by default, it's found that raid write performance
is quite bad because all IO are throttled by wbt of underlying disks,
due to flag REQ_IDLE is ignored. And turns out this behaviour exist since
blk-wbt is introduced.

Other than REQ_IDLE, other flags should not be ignored as well, for
example REQ_META can be set for filesystems, clearing it can cause priority
reverse problems; And REQ_NOWAIT should not be cleared as well, because
io will wait instead of failing directly in underlying disks.

Fix those problems by keep IO flags from master bio.

Fises: f51d46d0 ("md: add support for REQ_NOWAIT")
Fixes: e34cbd30 ("blk-wbt: add general throttling mechanism")
Fixes: 5404bc7a ("[PATCH] Allow file systems to differentiate between data and meta reads")
Link: https://lore.kernel.org/linux-raid/20250227121657.832356-1-yukuai1@huaweicloud.com


Signed-off-by: Yu Kuai <yukuai3@huawei.com>
[ Harshit: Resolve conflicts due to missing commit: f2a38abf
  ("md/raid1: Atomic write support") and  commit: a1d9b4fd
  ("md/raid10: Atomic write support") in 6.12.y, we don't have Atomic
  writes feature in 6.12.y ]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>