ide: Set BSY bit during FLUSH

ide: Set BSY bit during FLUSH

The implementation of the ATA FLUSH command invokes a flush at the block
layer, which may on raw files on POSIX entail a synchronous fdatasync().
This may in some cases take so long that the SLES 11 SP1 guest driver
reports I/O errors and filesystems get corrupted or remounted read-only.

Avoid this by setting BUSY_STAT, so that the guest is made aware we are
in the middle of an operation and no ATA commands are attempted to be
processed concurrently.

Addresses BNC#637297.

Suggested-by: Gonglei (Arei) <[email protected]>
Signed-off-by: Andreas Färber <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>