Some errors are ignored in the I/O path during queueing chunks
for processing by chunk works. Since at least these errors are
transient in nature, it should be possible to retry the failed
incoming commands.

The fix -

Errors that can happen while queueing chunks are carried upwards
to the main mapping function and it now returns DM_MAPIO_REQUEUE
for any incoming requests that can not be properly queued.

Error logging/debug messages are added where needed.

Fixes: 3b1a94c8 ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>