xfs: use bounce buffering direct I/O when the device requires stable pages

xfs: use bounce buffering direct I/O when the device requires stable pages

Fix direct I/O on devices that require stable pages by asking iomap
to bounce buffer.  To support this, ioends are used for direct reads
in this case to provide a user context for copying data back from the
bounce buffer.

This fixes qemu when used on devices using T10 protection information
and probably other cases like iSCSI using data digests.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Tested-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>