CVE-2026-43309: md raid: fix hang when stopping arrays with metadata through dm-raid

In the Linux kernel, the following vulnerability has been resolved: md raid: fix hang when stopping arrays with metadata through dm-raid When using device-mapper's dm-raid target, stopping a RAID array can cause the system to hang under specific conditions. This occurs when: - A dm-raid managed device tree is suspended from top to bottom (the top-level RAID device is suspended first, followed by its underlying metadata and data devices) - The top-level RAID device is then removed Removing the top-level device triggers a hang in the following sequence: the dm-raid destructor calls md_stop(), which tries to flush the write-intent bitmap by writing to the metadata sub-devices. However, these devices are already suspended, making them unable to complete the write-intent operations and causing an indefinite block. Fix: - Prevent bitmap flushing when md_stop() is called from dm-raid destructor context and avoid a quiescing/unquescing cycle which could also cause I/O - Still allow write-intent bitmap flushing when called from dm-raid suspend context This ensures that RAID array teardown can complete successfully even when the underlying devices are in a suspended state. This second patch uses md_is_rdwr() to distinguish between suspend and destructor paths as elaborated on above.