vhost-scsi: Add better resource allocation failure handling

[ Upstream commit 3ca51662 ]

If we can't allocate mem to map in data for a request or can't find
a tag for a command, we currently drop the command. This leads to the
error handler running to clean it up. Instead of dropping the command
this has us return an error telling the initiator that it queued more
commands than we can handle. The initiator will then reduce how many
commands it will send us and retry later.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20241203191705.19431-4-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Stable-dep-of: b1826871 ("vhost-scsi: Fix vhost_scsi_send_bad_target()")
Signed-off-by: Sasha Levin <sashal@kernel.org>